Acceleration feedback improves balancing against reflex delay
Insperger, Tamás; Milton, John; Stépán, Gábor
2013-01-01
A model for human postural balance is considered in which the time-delayed feedback depends on position, velocity and acceleration (proportional–derivative–acceleration (PDA) feedback). It is shown that a PDA controller is equivalent to a predictive controller, in which the prediction is based on the most recent information of the state, but the control input is not involved into the prediction. A PDA controller is superior to the corresponding proportional–derivative controller in the sense that the PDA controller can stabilize systems with approximately 40 per cent larger feedback delays. The addition of a sensory dead zone to account for the finite thresholds for detection by sensory receptors results in highly intermittent, complex oscillations that are a typical feature of human postural sway. PMID:23173196
Acceleration and torque feedback for robotic control - Experimental results
NASA Technical Reports Server (NTRS)
Mclnroy, John E.; Saridis, George N.
1990-01-01
Gross motion control of robotic manipulators typically requires significant on-line computations to compensate for nonlinear dynamics due to gravity, Coriolis, centripetal, and friction nonlinearities. One controller proposed by Luo and Saridis avoids these computations by feeding back joint acceleration and torque. This study implements the controller on a Puma 600 robotic manipulator. Joint acceleration measurement is obtained by measuring linear accelerations of each joint, and deriving a computationally efficient transformation from the linear measurements to the angular accelerations. Torque feedback is obtained by using the previous torque sent to the joints. The implementation has stability problems on the Puma 600 due to the extremely high gains inherent in the feedback structure. Since these high gains excite frequency modes in the Puma 600, the algorithm is modified to decrease the gain inherent in the feedback structure. The resulting compensator is stable and insensitive to high frequency unmodeled dynamics. Moreover, a second compensator is proposed which uses acceleration and torque feedback, but still allows nonlinear terms to be fed forward. Thus, by feeding the increment in the easily calculated gravity terms forward, improved responses are obtained. Both proposed compensators are implemented, and the real time results are compared to those obtained with the computed torque algorithm.
NASA Astrophysics Data System (ADS)
Deng, Chao; Ren, Wei; Mao, Yao; Ren, Ge
2017-08-01
A plug-in module acceleration feedback control (Plug-In AFC) strategy based on the disturbance observer (DOB) principle is proposed for charge-coupled device (CCD)-based fast steering mirror (FSM) stabilization systems. In classical FSM tracking systems, dual-loop control (DLC), including velocity feedback and position feedback, is usually utilized to enhance the closed-loop performance. Due to the mechanical resonance of the system and CCD time delay, the closed-loop bandwidth is severely restricted. To solve this problem, cascade acceleration feedback control (AFC), which is a kind of high-precision robust control method, is introduced to strengthen the disturbance rejection property. However, in practical applications, it is difficult to realize an integral algorithm in an acceleration controller to compensate for the quadratic differential contained in the FSM acceleration model, resulting in a challenging controller design and a limited improvement. To optimize the acceleration feedback framework in the FSM system, different from the cascade AFC, the accelerometers are used to construct DOB to compensate for the platform vibrations directly. The acceleration nested loop can be plugged into the velocity loop without changing the system stability, and the controller design is quite simple. A series of comparative experimental results demonstrate that the disturbance rejection property of the CCD-based FSM can be effectively improved by the proposed approach.
Effects of Grip-Force, Contact, and Acceleration Feedback on a Teleoperated Pick-and-Place Task.
Khurshid, Rebecca P; Fitter, Naomi T; Fedalei, Elizabeth A; Kuchenbecker, Katherine J
2017-01-01
The multifaceted human sense of touch is fundamental to direct manipulation, but technical challenges prevent most teleoperation systems from providing even a single modality of haptic feedback, such as force feedback. This paper postulates that ungrounded grip-force, fingertip-contact-and-pressure, and high-frequency acceleration haptic feedback will improve human performance of a teleoperated pick-and-place task. Thirty subjects used a teleoperation system consisting of a haptic device worn on the subject's right hand, a remote PR2 humanoid robot, and a Vicon motion capture system to move an object to a target location. Each subject completed the pick-and-place task 10 times under each of the eight haptic conditions obtained by turning on and off grip-force feedback, contact feedback, and acceleration feedback. To understand how object stiffness affects the utility of the feedback, half of the subjects completed the task with a flexible plastic cup, and the others used a rigid plastic block. The results indicate that the addition of grip-force feedback with gain switching enables subjects to hold both the flexible and rigid objects more stably, and it also allowed subjects who manipulated the rigid block to hold the object more delicately and to better control the motion of the remote robot's hand. Contact feedback improved the ability of subjects who manipulated the flexible cup to move the robot's arm in space, but it deteriorated this ability for subjects who manipulated the rigid block. Contact feedback also caused subjects to hold the flexible cup less stably, but the rigid block more securely. Finally, adding acceleration feedback slightly improved the subject's performance when setting the object down, as originally hypothesized; interestingly, it also allowed subjects to feel vibrations produced by the robot's motion, causing them to be more careful when completing the task. This study supports the utility of grip-force and high-frequency acceleration
Acceleration of tropical cyclogenesis by self-aggregation feedbacks
NASA Astrophysics Data System (ADS)
Muller, Caroline J.; Romps, David M.
2018-03-01
Idealized simulations of tropical moist convection have revealed that clouds can spontaneously clump together in a process called self-aggregation. This results in a state where a moist cloudy region with intense deep convection is surrounded by extremely dry subsiding air devoid of deep convection. Because of the idealized settings of the simulations where it was discovered, the relevance of self-aggregation to the real world is still debated. Here, we show that self-aggregation feedbacks play a leading-order role in the spontaneous genesis of tropical cyclones in cloud-resolving simulations. Those feedbacks accelerate the cyclogenesis process by a factor of 2, and the feedbacks contributing to the cyclone formation show qualitative and quantitative agreement with the self-aggregation process. Once the cyclone is formed, wind-induced surface heat exchange (WISHE) effects dominate, although we find that self-aggregation feedbacks have a small but nonnegligible contribution to the maintenance of the mature cyclone. Our results suggest that self-aggregation, and the framework developed for its study, can help shed more light into the physical processes leading to cyclogenesis and cyclone intensification. In particular, our results point out the importance of the longwave radiative cooling outside the cyclone.
Nataraj, Raviraj; Audu, Musa L; Triolo, Ronald J
2012-05-06
The purpose of this study was to determine the comparative effectiveness of feedback control systems for maintaining standing balance based on joint kinematics or total body center of mass (COM) acceleration, and assess their clinical practicality for standing neuroprostheses after spinal cord injury (SCI). In simulation, controller performance was measured according to the upper extremity effort required to stabilize a three-dimensional model of bipedal standing against a variety of postural disturbances. Three cases were investigated: proportional-derivative control based on joint kinematics alone, COM acceleration feedback alone, and combined joint kinematics and COM acceleration feedback. Additionally, pilot data was collected during external perturbations of an individual with SCI standing with functional neuromuscular stimulation (FNS), and the resulting joint kinematics and COM acceleration data was analyzed. Compared to the baseline case of maximal constant muscle excitations, the three control systems reduced the mean upper extremity loading by 51%, 43% and 56%, respectively against external force-pulse perturbations. Controller robustness was defined as the degradation in performance with increasing levels of input errors expected with clinical deployment of sensor-based feedback. At error levels typical for body-mounted inertial sensors, performance degradation due to sensor noise and placement were negligible. However, at typical tracking error levels, performance could degrade as much as 86% for joint kinematics feedback and 35% for COM acceleration feedback. Pilot data indicated that COM acceleration could be estimated with a few well-placed sensors and efficiently captures information related to movement synergies observed during perturbed bipedal standing following SCI. Overall, COM acceleration feedback may be a more feasible solution for control of standing with FNS given its superior robustness and small number of inputs required.
2012-01-01
Background The purpose of this study was to determine the comparative effectiveness of feedback control systems for maintaining standing balance based on joint kinematics or total body center of mass (COM) acceleration, and assess their clinical practicality for standing neuroprostheses after spinal cord injury (SCI). Methods In simulation, controller performance was measured according to the upper extremity effort required to stabilize a three-dimensional model of bipedal standing against a variety of postural disturbances. Three cases were investigated: proportional-derivative control based on joint kinematics alone, COM acceleration feedback alone, and combined joint kinematics and COM acceleration feedback. Additionally, pilot data was collected during external perturbations of an individual with SCI standing with functional neuromuscular stimulation (FNS), and the resulting joint kinematics and COM acceleration data was analyzed. Results Compared to the baseline case of maximal constant muscle excitations, the three control systems reduced the mean upper extremity loading by 51%, 43% and 56%, respectively against external force-pulse perturbations. Controller robustness was defined as the degradation in performance with increasing levels of input errors expected with clinical deployment of sensor-based feedback. At error levels typical for body-mounted inertial sensors, performance degradation due to sensor noise and placement were negligible. However, at typical tracking error levels, performance could degrade as much as 86% for joint kinematics feedback and 35% for COM acceleration feedback. Pilot data indicated that COM acceleration could be estimated with a few well-placed sensors and efficiently captures information related to movement synergies observed during perturbed bipedal standing following SCI. Conclusions Overall, COM acceleration feedback may be a more feasible solution for control of standing with FNS given its superior robustness and small
Xue, Chao; Quan, Li-Di; Yang, Shan-Qing; Wang, Bing-Peng; Wu, Jun-Fei; Shao, Cheng-Gang; Tu, Liang-Cheng; Milyukov, Vadim; Luo, Jun
2014-01-01
This paper describes the preliminary measurement of the Newtonian gravitational constant G with the angular acceleration feedback method at HUST. The apparatus has been built, and preliminary measurement performed, to test all aspects of the experimental design, particularly the feedback function, which was recently discussed in detail by Quan et al. The experimental results show that the residual twist angle of the torsion pendulum at the signal frequency introduces 0.4 ppm to the value of G. The relative uncertainty of the angular acceleration of the turntable is approximately 100 ppm, which is mainly limited by the stability of the apparatus. Therefore, the experiment has been modified with three features: (i) the height of the apparatus is reduced almost by half, (ii) the aluminium shelves were replaced with shelves made from ultra-low expansion material and (iii) a perfect compensation of the laboratory-fixed gravitational background will be carried out. With these improvements, the angular acceleration is expected to be determined with an uncertainty of better than 10 ppm, and a reliable value of G with 20 ppm or below will be obtained in the near future. PMID:25201996
Xue, Chao; Quan, Li-Di; Yang, Shan-Qing; Wang, Bing-Peng; Wu, Jun-Fei; Shao, Cheng-Gang; Tu, Liang-Cheng; Milyukov, Vadim; Luo, Jun
2014-10-13
This paper describes the preliminary measurement of the Newtonian gravitational constant G with the angular acceleration feedback method at HUST. The apparatus has been built, and preliminary measurement performed, to test all aspects of the experimental design, particularly the feedback function, which was recently discussed in detail by Quan et al. The experimental results show that the residual twist angle of the torsion pendulum at the signal frequency introduces 0.4 ppm to the value of G. The relative uncertainty of the angular acceleration of the turntable is approximately 100 ppm, which is mainly limited by the stability of the apparatus. Therefore, the experiment has been modified with three features: (i) the height of the apparatus is reduced almost by half, (ii) the aluminium shelves were replaced with shelves made from ultra-low expansion material and (iii) a perfect compensation of the laboratory-fixed gravitational background will be carried out. With these improvements, the angular acceleration is expected to be determined with an uncertainty of better than 10 ppm, and a reliable value of G with 20 ppm or below will be obtained in the near future. © 2014 The Author(s) Published by the Royal Society. All rights reserved.
2007-11-01
Control Theory Perspective of Effects-Based Thinking and Operations Modelling “Operations” as a Feedback Control System Philip S. E... Theory Perspective of Effects-Based Thinking and Operations Modelling “Operations” as a Feedback Control System Philip S. E. Farrell...Abstract This paper explores operations that involve effects-based thinking (EBT) using Control Theory techniques in order to highlight the concept’s
Carbon-climate feedbacks accelerate ocean acidification
NASA Astrophysics Data System (ADS)
Matear, Richard J.; Lenton, Andrew
2018-03-01
Carbon-climate feedbacks have the potential to significantly impact the future climate by altering atmospheric CO2 concentrations (Zaehle et al. 2010). By modifying the future atmospheric CO2 concentrations, the carbon-climate feedbacks will also influence the future ocean acidification trajectory. Here, we use the CO2 emissions scenarios from four representative concentration pathways (RCPs) with an Earth system model to project the future trajectories of ocean acidification with the inclusion of carbon-climate feedbacks. We show that simulated carbon-climate feedbacks can significantly impact the onset of undersaturated aragonite conditions in the Southern and Arctic oceans, the suitable habitat for tropical coral and the deepwater saturation states. Under the high-emissions scenarios (RCP8.5 and RCP6), the carbon-climate feedbacks advance the onset of surface water under saturation and the decline in suitable coral reef habitat by a decade or more. The impacts of the carbon-climate feedbacks are most significant for the medium- (RCP4.5) and low-emissions (RCP2.6) scenarios. For the RCP4.5 scenario, by 2100 the carbon-climate feedbacks nearly double the area of surface water undersaturated with respect to aragonite and reduce by 50 % the surface water suitable for coral reefs. For the RCP2.6 scenario, by 2100 the carbon-climate feedbacks reduce the area suitable for coral reefs by 40 % and increase the area of undersaturated surface water by 20 %. The sensitivity of ocean acidification to the carbon-climate feedbacks in the low to medium emission scenarios is important because recent CO2 emission reduction commitments are trying to transition emissions to such a scenario. Our study highlights the need to better characterise the carbon-climate feedbacks and ensure we do not underestimate the projected ocean acidification.
Optimized operation of dielectric laser accelerators: Multibunch
NASA Astrophysics Data System (ADS)
Hanuka, Adi; Schächter, Levi
2018-06-01
We present a self-consistent analysis to determine the optimal charge, gradient, and efficiency for laser driven accelerators operating with a train of microbunches. Specifically, we account for the beam loading reduction on the material occurring at the dielectric-vacuum interface. In the case of a train of microbunches, such beam loading effect could be detrimental due to energy spread, however this may be compensated by a tapered laser pulse. We ultimately propose an optimization procedure with an analytical solution for group velocity which equals to half the speed of light. This optimization results in a maximum efficiency 20% lower than the single bunch case, and a total accelerated charge of 1 06 electrons in the train. The approach holds promise for improving operations of dielectric laser accelerators and may have an impact on emerging laser accelerators driven by high-power optical lasers.
NASA Astrophysics Data System (ADS)
Strathdee, A.
1985-10-01
The topics discussed are related to high-energy accelerators and colliders, particle sources and electrostatic accelerators, controls, instrumentation and feedback, beam dynamics, low- and intermediate-energy circular accelerators and rings, RF and other acceleration systems, beam injection, extraction and transport, operations and safety, linear accelerators, applications of accelerators, radiation sources, superconducting supercolliders, new acceleration techniques, superconducting components, cryogenics, and vacuum. Accelerator and storage ring control systems are considered along with linear and nonlinear orbit theory, transverse and longitudinal instabilities and cures, beam cooling, injection and extraction orbit theory, high current dynamics, general beam dynamics, and medical and radioisotope applications. Attention is given to superconducting RF structures, magnet technology, superconducting magnets, and physics opportunities with relativistic heavy ion accelerators.
Operating room metrics score card-creating a prototype for individualized feedback.
Gabriel, Rodney A; Gimlich, Robert; Ehrenfeld, Jesse M; Urman, Richard D
2014-11-01
The balance between reducing costs and inefficiencies with that of patient safety is a challenging problem faced in the operating room suite. An ongoing challenge is the creation of effective strategies that reduce these inefficiencies and provide real-time personalized metrics and electronic feedback to anesthesia practitioners. We created a sample report card structure, utilizing existing informatics systems. This system allows to gather and analyze operating room metrics for each anesthesia provider and offer personalized feedback. To accomplish this task, we identified key metrics that represented time and quality parameters. We collected these data for individual anesthesiologists and compared performance to the overall group average. Data were presented as an electronic score card and made available to individual clinicians on a real-time basis in an effort to provide effective feedback. These metrics included number of cancelled cases, average turnover time, average time to operating room ready and patient in room, number of delayed first case starts, average induction time, average extubation time, average time to recovery room arrival to discharge, performance feedback from other providers, compliance to various protocols, and total anesthetic costs. The concept we propose can easily be generalized to a variety of operating room settings, types of facilities and OR health care professionals. Such a scorecard can be created using content that is important for operating room efficiency, research, and practice improvement for anesthesia providers.
Operational Characteristics of an Accelerator Driven Fissile Solution System
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kimpland, Robert Herbert
Operational characteristics represent the set of responses that a nuclear system exhibits during normal operation. Operators rely on this behavior to assess the status of the system and to predict the consequences of off-normal events. These characteristics largely refer to the relationship between power and system operating conditions. The static and dynamic behavior of a chain-reacting system, operating at sufficient power, is primarily governed by reactivity effects. The science of reactor physics has identified and evaluated a number of such effects, including Doppler broadening and shifts in the thermal neutron spectrum. Often these reactivity effects are quantified in the formmore » of feedback coefficients that serve as coupling coefficients relating the neutron population and the physical mechanisms that drive reactivity effects, such as fissile material temperature and density changes. The operational characteristics of such nuclear systems usually manifest themselves when perturbations between system power (neutron population) and system operating conditions arise. Successful operation of such systems requires the establishment of steady equilibrium conditions. However, prior to obtaining the desired equilibrium (steady-state) conditions, an approach from zero-power (startup) must occur. This operational regime may possess certain limiting system conditions that must be maintained to achieve effective startup. Once steady-state is achieved, a key characteristic of this operational regime is the level of stability that the system possesses. Finally, a third operational regime, shutdown, may also possess limiting conditions of operation that must be maintained. This report documents the operational characteristics of a “generic” Accelerator Driven Fissile Solution (ADFS) system during the various operational regimes of startup, steady-state operation, and shutdown. Typical time-dependent behavior for each operational regime will be illustrated, and
Feedbacks between Reservoir Operation and Floodplain Development
NASA Astrophysics Data System (ADS)
Wallington, K.; Cai, X.
2017-12-01
The increased connectedness of socioeconomic and natural systems warrants the study of them jointly as Coupled Natural-Human Systems (CNHS) (Liu et al., 2007). One such CNHS given significant attention in recent years has been the coupled sociological-hydrological system of floodplains. Di Baldassarre et al. (2015) developed a model coupling floodplain development and levee heightening, a flood control measure, which demonstrated the "levee effect" and "adaptation effect" seen in observations. Here, we adapt the concepts discussed by Di Baldassarre et al. (2015) and apply them to floodplains in which the primary flood control measure is reservoir storage, rather than levee construction, to study the role of feedbacks between reservoir operation and floodplain development. Specifically, we investigate the feedback between floodplain development and optimal management of trade-offs between flood water conservation and flood control. By coupling a socio-economic model based on that of Di Baldassarre et al. (2015) with a reservoir optimization model based on that discussed in Ding et al. (2017), we show that reservoir operation rules can co-evolve with floodplain development. Furthermore, we intend to demonstrate that the model results are consistent with real-world data for reservoir operating curves and floodplain development. This model will help explain why some reservoirs are currently operated for purposes which they were not originally intended and thus inform reservoir design and construction.
NASA Technical Reports Server (NTRS)
Kirkpatrick, M.; Brye, R. G.
1974-01-01
A motion cue investigation program is reported that deals with human factor aspects of high fidelity vehicle simulation. General data on non-visual motion thresholds and specific threshold values are established for use as washout parameters in vehicle simulation. A general purpose similator is used to test the contradictory cue hypothesis that acceleration sensitivity is reduced during a vehicle control task involving visual feedback. The simulator provides varying acceleration levels. The method of forced choice is based on the theory of signal detect ability.
Surface-plasmon distributed-feedback quantum cascade lasers operating pulsed, room temperature
NASA Astrophysics Data System (ADS)
Bousseksou, A.; Chassagneux, Y.; Coudevylle, J. R.; Colombelli, R.; Sirtori, C.; Patriarche, G.; Beaudoin, G.; Sagnes, I.
2009-08-01
We report distributed-feedback surface-plasmon quantum cascade lasers operating at λ ≈7.6μm. The distributed feedback is obtained by the sole patterning of the top metal contact on a surface plasmon waveguide. Single mode operation with more than 30dB side mode suppression ratio is obtained in pulsed mode and at room temperature. A careful experimental study confirms that by varying the grating duty cycle, one can reduce the waveguide losses with respect to standard, unpatterned surface-plasmon devices. This allows one to reduce the laser threshold current of more than a factor of 2 in the 200-300K temperature range. This approach may lead to a fabrication technology for midinfrared distributed-feedback lasers based on a very simple processing.
Theory of repetitively pulsed operation of diode lasers subject to delayed feedback
DOE Office of Scientific and Technical Information (OSTI.GOV)
Napartovich, A P; Sukharev, A G
2015-03-31
Repetitively pulsed operation of a diode laser with delayed feedback has been studied theoretically at varying feedback parameters and pump power levels. A new approach has been proposed that allows one to reduce the system of Lang–Kobayashi equations for a steady-state repetitively pulsed operation mode to a first-order nonlinear differential equation. We present partial solutions that allow the pulse shape to be predicted. (lasers)
Accelerator/Experiment Operations - FY 2014
DOE Office of Scientific and Technical Information (OSTI.GOV)
Czarapata, P.; Geer, S.; Geesaman, D.
2014-10-01
This Technical Memorandum (TM) summarizes the Fermilab accelerator and accelerator experiment operations for FY 2014. It is one of a series of annual publications intended to gather information in one place. In this case, the information concerns the FY 2014 MINOS and MINERvA experiments using the Main Injector Neutrino Beam (NuMI), the MiniBooNE experiment running in the Booster Neutrino Beam (BNB), and the SeaQuest experiment and Meson Test Beam (MTest) activities in the 120 GeV external Switchyard beam (SY120). Each section was prepared by the relevant authors, and was somewhat edited for inclusion in this summary.
Development of wide area environment accelerator operation and diagnostics method
NASA Astrophysics Data System (ADS)
Uchiyama, Akito; Furukawa, Kazuro
2015-08-01
Remote operation and diagnostic systems for particle accelerators have been developed for beam operation and maintenance in various situations. Even though fully remote experiments are not necessary, the remote diagnosis and maintenance of the accelerator is required. Considering remote-operation operator interfaces (OPIs), the use of standard protocols such as the hypertext transfer protocol (HTTP) is advantageous, because system-dependent protocols are unnecessary between the remote client and the on-site server. Here, we have developed a client system based on WebSocket, which is a new protocol provided by the Internet Engineering Task Force for Web-based systems, as a next-generation Web-based OPI using the Experimental Physics and Industrial Control System Channel Access protocol. As a result of this implementation, WebSocket-based client systems have become available for remote operation. Also, as regards practical application, the remote operation of an accelerator via a wide area network (WAN) faces a number of challenges, e.g., the accelerator has both experimental device and radiation generator characteristics. Any error in remote control system operation could result in an immediate breakdown. Therefore, we propose the implementation of an operator intervention system for remote accelerator diagnostics and support that can obviate any differences between the local control room and remote locations. Here, remote-operation Web-based OPIs, which resolve security issues, are developed.
Continuous wave operation of quantum cascade lasers with frequency-shifted feedback
DOE Office of Scientific and Technical Information (OSTI.GOV)
Lyakh, A., E-mail: arkadiy.lyakh@ucf.edu; NanoScience Technology Center, University of Central Florida, 12424 Research Pkwy, Orlando, FL 32826; College of Optics and Photonics, University of Central Florida, 304 Scorpius St, Orlando, FL 32826
2016-01-15
Operation of continuous wave quantum cascade lasers with a frequency-shifted feedback provided by an acousto-optic modulator is reported. Measured linewidth of 1.7 cm{sup −1} for these devices, under CW operating conditions, was in a good agreement with predictions of a model based on frequency-shifted feedback seeded by spontaneous emission. Linewidth broadening was observed for short sweep times, consistent with sound wave grating period variation across the illuminated area on the acousto-optic modulator. Standoff detection capability of the AOM-based QCL setup was demonstrated for several solid materials.
Operating experience feedback report: New plants, Commercial power reactors
DOE Office of Scientific and Technical Information (OSTI.GOV)
Dennig, R.L.; O'Reilly, P.D.
1987-07-01
This report documents a detailed review of the cause of unplanned events during the early months of licensed operation for plants licensed between March 1983 and April 1986. The major lessons and corrective actions that appear to have the greatest potential for improving the effectiveness of plant startups are provided for consideration through the operating experience feedback programs and activities of the industry and the NRC staff.
Accelerated recovery after cardiac operations.
Kaplan, Mehmet; Kut, Mustafa Sinan; Yurtseven, Nurgul; Cimen, Serdar; Demirtas, Mahmut Murat
2002-01-01
The accelerated-recovery approach, involving early extubation, early mobility, decreased duration of intensive care unit stay, and decreased duration of hospitalization has recently become a controversial issue in cardiac surgery. We investigated timing of extubation, length of intensive care unit stay, and duration of hospitalization in 225 consecutive cardiac surgery patients. Of the 225 patients, 139 were male and 86 were female; average age was 49.73 +/- 16.95 years. Coronary artery bypass grafting was performed in 127 patients; 65 patients underwent aortic and/or mitral or pulmonary valvular operations; 5 patients underwent valvular plus coronary artery operations; and in 28 patients surgical interventions for congenital anomalies were carried out. The accelerated-recovery approach could be applied in 169 of the 225 cases (75.11%). Accelerated-recovery patients were extubated after an average of 3.97 +/- 1.59 hours, and the average duration of stay in the intensive care unit was 20.93 +/- 2.44 hours for these patients. Patients were discharged if they met all of the following criteria: hemodynamic stability, cooperativeness, ability to initiate walking exercises within wards, lack of pathology in laboratory investigations, and psychological readiness for discharge. Mean duration of hospitalization for accelerated-recovery patients was 4.24 +/- 0.75 days. Two patients (1.18%) who were extubated within the first 6 hours required reintubation. Four patients (2.36%) who were sent to the wards returned to intensive care unit due to various reasons and 6 (3.55%) of the discharged patients were rehospitalized. Approaches for decreasing duration of intubation, intensive care unit stay and hospitalization may be applied in elective and uncomplicated cardiac surgical interventions with short duration of aortic cross-clamping and cardiopulmonary bypass, without risking patients. Frequencies of reintubation, return to intensive care unit, and rehospitalization are quite
Feedback-Assisted Extension of the Tokamak Operating Space to Low Safety Factor
NASA Astrophysics Data System (ADS)
Hanson, J. M.
2013-10-01
Recent DIII-D experiments have demonstrated stable operation at very low edge safety factor, q95 <~ 2 through the use of magnetic feedback to control the n = 1 resistive wall mode (RWM) instability. The performance of tokamak fusion devices may benefit from increased plasma current, and thus, decreased q. However, disruptive stability limits are commonly encountered in experiments at qedge ~ 2 (limited plasmas) and q95 ~ 2 (diverted plasmas), limiting exploration of low q regimes. In the recent DIII-D experiments, the impact and control of key disruptive instabilities was studied. Locked n = 1 modes with exponential growth times on the order of the wall eddy current decay timescale τw preceded disruptions at q95 = 2 . The instabilities have a poloidal structure that is consistent with VALEN simulations of the RWM mode structure at q95 = 2 . Applying proportional gain magnetic feedback control of the n = 1 mode resulted in stabilized operation with q95 reaching 1.9, and an extension of the discharge lifetime for > 100τw . Loss of feedback control was accompanied by power supply saturation, followed by a rapidly growing n = 1 mode and disruption. Comparisons of the feedback dynamics with VALEN simulations will be presented. The DIII-D results complement and will be discussed alongside recent RFX-MOD demonstrations of RWM control using magnetic feedback in limited tokamak discharges with qedge < 2. These results call attention to the utility of magnetic feedback in significantly extending the tokamak operational space and potentially opening a new route to economical fusion power production. Supported by the US Department of Energy under DE-FG02-04ER54761 and DE-FC02-04ER54698.
Bello, Ricardo J; Sarmiento, Samuel; Meyer, Meredith L; Rosson, Gedge D; Cooney, Damon S; Lifchez, Scott D; Cooney, Carisa M
2018-04-20
Operative performance feedback is essential for surgical training. We aimed to understand surgical trainees' views on their operative performance feedback needs and to characterize feedback to elucidate factors affecting its value from the resident perspective. Using a qualitative research approach, 2 research fellows conducted semistructured, one-on-one interviews with surgical trainees. We analyzed recurring themes generated during interviews related to feedback characteristics, as well as the extent to which performance rating tools can help meet trainees' operative feedback needs. Departments or divisions of general or plastic surgery at 9 US academic institutions. Surgical residents and clinical fellows in general or plastic surgery. We conducted 30 interviews with 9 junior residents, 14 senior residents, and 7 clinical fellows. Eighteen (60%) participants were in plastic and 12 (40%) were in general surgery. Twenty-four participants (80%) reported feedback as very or extremely important during surgical training. All trainees stated that verbal, face-to-face feedback is the most valuable, especially if occurring during (92%) or immediately after (65%) cases. Of those trainees using performance rating tools (74%), most (57%) expressed positive views about them but wanted the tools to complement and not replace verbal feedback in surgical education. Trainees value feedback more if received within 1 week or the case. Verbal, face-to-face feedback is very or extremely important to surgical trainees. Residents and fellows prefer to receive feedback during or immediately after a case and continue to value feedback if received within 1 week of the event. Performance rating tools can be useful for providing formative feedback and documentation but should not replace verbal, face-to-face feedback. Considering trainee views on feedback may help reduce perceived gaps in feedback demand-versus-supply in surgical training, which may be essential to overcoming current
Pope, K.E.
1958-01-01
This patent relates to an improved acceleration integrator and more particularly to apparatus of this nature which is gyrostabilized. The device may be used to sense the attainment by an airborne vehicle of a predetermined velocitv or distance along a given vector path. In its broad aspects, the acceleration integrator utilizes a magnetized element rotatable driven by a synchronous motor and having a cylin drical flux gap and a restrained eddy- current drag cap deposed to move into the gap. The angular velocity imparted to the rotatable cap shaft is transmitted in a positive manner to the magnetized element through a servo feedback loop. The resultant angular velocity of tae cap is proportional to the acceleration of the housing in this manner and means may be used to measure the velocity and operate switches at a pre-set magnitude. To make the above-described dcvice sensitive to acceleration in only one direction the magnetized element forms the spinning inertia element of a free gyroscope, and the outer housing functions as a gimbal of a gyroscope.
Visual feedback system to reduce errors while operating roof bolting machines
Steiner, Lisa J.; Burgess-Limerick, Robin; Eiter, Brianna; Porter, William; Matty, Tim
2015-01-01
Problem Operators of roof bolting machines in underground coal mines do so in confined spaces and in very close proximity to the moving equipment. Errors in the operation of these machines can have serious consequences, and the design of the equipment interface has a critical role in reducing the probability of such errors. Methods An experiment was conducted to explore coding and directional compatibility on actual roof bolting equipment and to determine the feasibility of a visual feedback system to alert operators of critical movements and to also alert other workers in close proximity to the equipment to the pending movement of the machine. The quantitative results of the study confirmed the potential for both selection errors and direction errors to be made, particularly during training. Results Subjective data confirmed a potential benefit of providing visual feedback of the intended operations and movements of the equipment. Impact This research may influence the design of these and other similar control systems to provide evidence for the use of warning systems to improve operator situational awareness. PMID:23398703
Operational and design aspects of accelerators for medical applications
NASA Astrophysics Data System (ADS)
Schippers, Jacobus Maarten; Seidel, Mike
2015-03-01
Originally, the typical particle accelerators as well as their associated beam transport equipment were designed for particle and nuclear physics research and applications in isotope production. In the past few decades, such accelerators and related equipment have also been applied for medical use. This can be in the original physics laboratory environment, but for the past 20 years also in hospital-based or purely clinical environments for particle therapy. The most important specific requirements of accelerators for radiation therapy with protons or ions will be discussed. The focus will be on accelerator design, operational, and formal aspects. We will discuss the special requirements to reach a high reliability for patient treatments as well as an accurate delivery of the dose at the correct position in the patient using modern techniques like pencil beam scanning. It will be shown that the technical requirements, safety aspects, and required reliability of the accelerated beam differ substantially from those in a nuclear physics laboratory. It will be shown that this difference has significant implications on the safety and interlock systems. The operation of such a medical facility should be possible by nonaccelerator specialists at different operating sites (treatment rooms). The organization and role of the control and interlock systems can be considered as being the most crucially important issue, and therefore a special, dedicated design is absolutely necessary in a facility providing particle therapy.
Vibrotactile Feedback for Brain-Computer Interface Operation
Cincotti, Febo; Kauhanen, Laura; Aloise, Fabio; Palomäki, Tapio; Caporusso, Nicholas; Jylänki, Pasi; Mattia, Donatella; Babiloni, Fabio; Vanacker, Gerolf; Nuttin, Marnix; Marciani, Maria Grazia; Millán, José del R.
2007-01-01
To be correctly mastered, brain-computer interfaces (BCIs) need an uninterrupted flow of feedback to the user. This feedback is usually delivered through the visual channel. Our aim was to explore the benefits of vibrotactile feedback during users' training and control of EEG-based BCI applications. A protocol for delivering vibrotactile feedback, including specific hardware and software arrangements, was specified. In three studies with 33 subjects (including 3 with spinal cord injury), we compared vibrotactile and visual feedback, addressing: (I) the feasibility of subjects' training to master their EEG rhythms using tactile feedback; (II) the compatibility of this form of feedback in presence of a visual distracter; (III) the performance in presence of a complex visual task on the same (visual) or different (tactile) sensory channel. The stimulation protocol we developed supports a general usage of the tactors; preliminary experimentations. All studies indicated that the vibrotactile channel can function as a valuable feedback modality with reliability comparable to the classical visual feedback. Advantages of using a vibrotactile feedback emerged when the visual channel was highly loaded by a complex task. In all experiments, vibrotactile feedback felt, after some training, more natural for both controls and SCI users. PMID:18354734
NASA Astrophysics Data System (ADS)
Poehlman, W. F. S.; Garland, Wm. J.; Stark, J. W.
1993-06-01
In an era of downsizing and a limited pool of skilled accelerator personnel from which to draw replacements for an aging workforce, the impetus to integrate intelligent computer automation into the accelerator operator's repertoire is strong. However, successful deployment of an "Operator's Companion" is not trivial. Both graphical and human factors need to be recognized as critical areas that require extra care when formulating the Companion. They include interactive graphical user's interface that mimics, for the operator, familiar accelerator controls; knowledge of acquisition phases during development must acknowledge the expert's mental model of machine operation; and automated operations must be seen as improvements to the operator's environment rather than threats of ultimate replacement. Experiences with the PACES Accelerator Operator Companion developed at two sites over the past three years are related and graphical examples are given. The scale of the work involves multi-computer control of various start-up/shutdown and tuning procedures for Model FN and KN Van de Graaff accelerators. The response from licensing agencies has been encouraging.
NASA Technical Reports Server (NTRS)
Darroy, Jean Michel
1993-01-01
Current trends in the spacecraft mission operations area (spacecraft & mission complexity, project duration, required flexibility are requiring a breakthrough for what concerns philosophy, organization, and support tools. A major evolution is related to space operations 'informationalization', i.e adding to existing operations support & data processing systems a new generation of tools based on advanced information technologies (object-oriented programming, artificial intelligence, data bases, hypertext) that automate, at least partially, operations tasks that used be performed manually (mission & project planning/scheduling, operations procedures elaboration & execution, data analysis & failure diagnosis). All the major facets of this 'informationalization' are addressed at MATRA MARCONI SPACE, operational applications were fielded and generic products are becoming available. These various applications have generated a significant feedback from the users (at ESA, CNES, ARIANESPACE, MATRA MARCONI SPACE), which is now allowing us to precisely measure how the deployment of this new generation of tools, that we called OPSWARE, can 'reengineer' current spacecraft mission operations philosophy, how it can make space operations faster, better, and cheaper. This paper can be considered as an update of the keynote address 'Knowledge-Based Systems for Spacecraft Control' presented during the first 'Ground Data Systems for Spacecraft Control' conference in Darmstadt, June 1990, with a special emphasis on these last two years users feedback.
Karim, Azad S; Sternbach, Joel M; Bender, Edward M; Zwischenberger, Joseph B; Meyerson, Shari L
Residents frequently report inadequate feedback both in quantity and quality. The study evaluates the quality of faculty feedback about operative performance given using an app-based system. Residents requested operative performance evaluation from faculty on a real-time basis using the "Zwisch Me!!" mobile application which allows faculty to provide brief written feedback. Qualitative analysis of feedback was performed using grounded theory. The 7 academic medical centers with thoracic surgery training programs. Volunteer thoracic surgery residents in both integrated and traditional training pathways and their affiliated cardiothoracic faculty. Residents (n = 33) at 7 institutions submitted a total of 596 evaluations to faculty (n = 48). Faculty acknowledged the evaluation request in 476 cases (80%) and in 350 cases (74%) provided written feedback. Initial open coding generated 12 categories of feedback type. We identified 3 overarching themes. The first theme was the tone of the feedback. Encouraging elements were identified in 162 comments (46%) and corrective elements in 230 (65%). The second theme was the topic of the feedback. Surgical technique was the most common category at 148 comments (42.2%) followed by preparation for case (n = 69, 19.7%). The final theme was the specificity of the feedback. Just over half of comments (n = 190, 54.3%) contained specific feedback, which could be applied to future cases. However, 51 comments (14.6%) contained no useful information for the learners. An app-based system resulted in thoracic surgery residents receiving identifiable feedback in a high proportion of cases. In over half of comments the feedback was specific enough to allow improvement. Feedback was better quality when addressing error prevention and surgical technique but was less useful when addressing communication, flow of the case, and assisting. Faculty development around feedback should focus on making feedback specific and actionable, avoiding case
Auditory display as feedback for a novel eye-tracking system for sterile operating room interaction.
Black, David; Unger, Michael; Fischer, Nele; Kikinis, Ron; Hahn, Horst; Neumuth, Thomas; Glaser, Bernhard
2018-01-01
The growing number of technical systems in the operating room has increased attention on developing touchless interaction methods for sterile conditions. However, touchless interaction paradigms lack the tactile feedback found in common input devices such as mice and keyboards. We propose a novel touchless eye-tracking interaction system with auditory display as a feedback method for completing typical operating room tasks. Auditory display provides feedback concerning the selected input into the eye-tracking system as well as a confirmation of the system response. An eye-tracking system with a novel auditory display using both earcons and parameter-mapping sonification was developed to allow touchless interaction for six typical scrub nurse tasks. An evaluation with novice participants compared auditory display with visual display with respect to reaction time and a series of subjective measures. When using auditory display to substitute for the lost tactile feedback during eye-tracking interaction, participants exhibit reduced reaction time compared to using visual-only display. In addition, the auditory feedback led to lower subjective workload and higher usefulness and system acceptance ratings. Due to the absence of tactile feedback for eye-tracking and other touchless interaction methods, auditory display is shown to be a useful and necessary addition to new interaction concepts for the sterile operating room, reducing reaction times while improving subjective measures, including usefulness, user satisfaction, and cognitive workload.
Environmental Impact From Accelerator Operation at SLAC
DOE Office of Scientific and Technical Information (OSTI.GOV)
Liu, James C
1999-03-22
Environmental impacts from electron accelerator operations at the Stanford Linear Accelerator Center, which is located near populated areas, are illustrated by using examples of three different accelerator facilities: the low power (a few watts) SSRL, the high power (a few kilowatts) PEP-II, and the 50-kW SLC. Three types of major impacts are discussed: (1) off-site doses from skyshine radiation, mainly neutrons, (2) off-site doses from radioactive air emission, mainly {sup 13}N, and (3) radioactivities, mainly {sup 3}H, produced in the groundwater. It was found that, from SSRL operation, the skyshine radiation result in a MEI (Maximum Exposed Individual) of 0.3more » {mu}Sv/y while a conservative calculation using CAP88 showed a MEI of 0.36 {mu}Sv/y from radioactive air releases. The calculated MEI doses due to future PEP-II operation are 30 {mu}Sv/y from skyshine radiation and 2 {mu}Sv/y from air releases. The population doses due to radioactive air emission are 0.5 person-mSv from SSRL and 12 person-mSv from PEP-II. Because of the stronger decrease of skyshine dose as the distance increases, the population dose from skyshine radiation are smaller than that from air release. The third environmental impact, tritium activity produced in the groundwater, was also demonstrated to be acceptable from both the well water measurements and the FLUKA calculations for the worst case of the SLC high-power dump.« less
Operation regimes of a dielectric laser accelerator
NASA Astrophysics Data System (ADS)
Hanuka, Adi; Schächter, Levi
2018-04-01
We investigate three operation regimes in dielectric laser driven accelerators: maximum efficiency, maximum charge, and maximum loaded gradient. We demonstrate, using a self-consistent approach, that loaded gradients of the order of 1 to 6 [GV/m], efficiencies of 20% to 80%, and electrons flux of 1014 [el/s] are feasible, without significant concerns regarding damage threshold fluence. The latter imposes that the total charge per squared wavelength is constant (a total of 106 per μm2). We conceive this configuration as a zero-order design that should be considered for the road map of future accelerators.
Moore, Maureen D; Abelson, Jonathan S; O'Mahoney, Paul; Bagautdinov, Iskander; Yeo, Heather; Watkins, Anthony C
As an adjunct to simulation-based teaching, laparoscopic video-based surgical coaching has been an effective tool to augment surgical education. However, the wide use of video review in open surgery has been limited primarily due to technological and logistical challenges. The aims of our study were to (1) evaluate perceptions of general surgery (GS) residents on video-assisted operative instruction and (2) conduct a pilot study using a head-mounted GoPro in conjunction with the operative performance rating system to assess feasibility of providing video review to enhance operative feedback during open procedures. GS residents were anonymously surveyed to evaluate their perceptions of oral and written operative feedback and use of video-based operative resources. We then conducted a pilot study of 10 GS residents to assess the utility and feasibility of using a GoPro to record resident performance of an arteriovenous fistula creation with an attending surgeon. Categorical variables were analyzed using the chi-square test. Academic, tertiary medical center. GS residents and faculty. A total of 59 GS residents were anonymously surveyed (response rate = 65.5%). A total of 40% (n = 24) of residents reported that structured evaluations rarely or never provided meaningful feedback. When feedback was received, 55% (n = 32) residents reported that it was only rarely or sometimes in regard to their operative skills. There was no significant difference in surveyed responses among junior postgraduate year (PGY 1-2), senior (PGY 3-4), or chief residents (PGY-5). A total of 80% (n = 8) of residents found the use of GoPro video review very or extremely useful for education; they also deemed video review more useful for operative feedback than written or communicative feedback. An overwhelming majority (90%, n = 9) felt that video review would lead to improved technical skills, wanted to review the video with the attending surgeon for further feedback, and desired expansion of
Operation of polycarbonate projectiles in the ram accelerator
NASA Astrophysics Data System (ADS)
Elder, Timothy
The ram accelerator is a hypervelocity launcher with direct space launch applications in which a sub-caliber projectile, analogous to the center-body of a ramjet engine, flies through fuel and oxidizer that have been premixed in a tube. Shock interactions in the tube ignite the propellant upon entrance of the projectile and the combustion travels with it, creating thrust on the projectile by stabilizing a high pressure region of gas behind it. Conventional ram accelerator projectiles consist of aluminum, magnesium, or titanium nosecones and bodies. An experimental program has been undertaken to determine the performance of polycarbonate projectiles in ram accelerator operation. Experimentation using polycarbonate projectiles has been divided into two series: determining the lower limit for starting velocity (i.e., less than 1100 m/s) and investigating the upper velocity limit. To investigate the influence of body length and starting velocity, a newly developed "combustion gun" was used to launch projectiles to their initial velocities. The combustion gun uses 3-6 m of ram accelerator test section as a breech and 4-6 m of the ram accelerator test section as a launch tube. A fuel-oxidizer mix is combusted in the breech using a spark plug or electric match and bursts a diaphragm, accelerating the ram projectile to its entrance velocity. The combustion gun can be operated at modest fill pressures (20 bar) but can only launch to relatively low velocities (approximately 1000 m/s) without destroying the projectile and obturator upon launch. Projectiles were successfully started at entrance velocities as low as 810 m/s and projectile body lengths as long as 91 mm were used. The tests investigating the upper Mach number limits of polycarbonate projectiles used the conventional single-stage light-gas gun because of its ability to reach higher velocities with a lower acceleration launch. It was determined that polycarbonate projectiles have an upper velocity limit in the
Operator control systems and methods for swing-free gantry-style cranes
Feddema, J.T.; Petterson, B.J.; Robinett, R.D. III
1998-07-28
A system and method are disclosed for eliminating swing motions in gantry-style cranes while subject to operator control. The present invention comprises an infinite impulse response (IIR) filter and a proportional-integral (PI) feedback controller. The IIR filter receives input signals (commanded velocity or acceleration) from an operator input device and transforms them into output signals in such a fashion that the resulting motion is swing free (i.e., end-point swinging prevented). The parameters of the IIR filter are updated in real time using measurements from a hoist cable length encoder. The PI feedback controller compensates for modeling errors and external disturbances, such as wind or perturbations caused by collision with objects. The PI feedback controller operates on cable swing angle measurements provided by a cable angle sensor. The present invention adjusts acceleration and deceleration to eliminate oscillations. An especially important feature of the present invention is that it compensates for variable-length cable motions from multiple cables attached to a suspended payload. 10 figs.
Antiproton acceleration in the Fermilab Main Ring and Tevatron
DOE Office of Scientific and Technical Information (OSTI.GOV)
Martin, P.; Dinkel, J.; Ducar, R.
1987-03-01
The operation of the Fermilab Main Ring and Tevatron rf systems for colliding beams physics is discussed. The changes in the rf feedback system required for the accelration of antiprotons, and the methods for achieving proper transfer of both protons and antiprotons are described. Data on acceleration and transfer efficiencies are presented.
Accelerator/Experiment Operations - FY 2015
DOE Office of Scientific and Technical Information (OSTI.GOV)
Czarapata, P.
2015-10-01
This Technical Memorandum summarizes the Fermilab accelerator and experiment operations for FY 2015. It is one of a series of annual publications intended to gather information in one place. In this case, the information concerns the FY 2015 NOvA, MINOS+ and MINERvA experiments using the Main Injector Neutrino Beam (NuMI), the activities in the SciBooNE Hall using the Booster Neutrino Beam (BNB), and the SeaQuest experiment and Meson Test Beam (MTest) activities in the 120 GeV external Switchyard beam (SY120).
NASA Astrophysics Data System (ADS)
Tang, Tao; Zhang, Tong; Du, Jun-Feng; Ren, Ge; Tian, Jing
2016-11-01
This paper proposes a dual-motor configuration to enhance closed-loop performance of a telescope control system. Two identical motors are mounted on each side of a U-type frame to drive the telescope elevation axis instead of a single motor drive, which is usually used in a classical design. This new configuration and mechanism can reduce the motor to half the size used in the former design, and it also provides some other advantages. A master-slave current control mode is employed to synchronize the two motors. Acceleration feedback control is utilized to further enhance the servo performance. Extensive experiments are used to validate the effectiveness of the proposed control algorithm in synchronization, disturbance attenuation and low-velocity tracking.
Enabling cost-effective high-current burst-mode operation in superconducting accelerators
Sheffield, Richard L.
2015-06-01
Superconducting (SC) accelerators are very efficient for CW or long-pulse operation, and normal conducting (NC) accelerators are cost effective for short-pulse operation. The addition of a short NC linac section to a SC linac can correct for the energy droop that occurs when pulsed high-current operation is required that exceeds the capability of the klystrons to replenish the cavity RF fields due to the long field fill-times of SC structures, or a requirement to support a broad range of beam currents results in variable beam loading. This paper describes the implementation of this technique to enable microseconds of high beam-current,more » 90 mA or more, in a 12 GeV SC long-pulse accelerator designed for the MaRIE 42-keV XFEL proposed for Los Alamos National Laboratory.« less
Tested by Fire - How two recent Wildfires affected Accelerator Operations at LANL
DOE Office of Scientific and Technical Information (OSTI.GOV)
Spickermann, Thomas
2012-08-01
In a little more than a decade two large wild fires threatened Los Alamos and impacted accelerator operations at LANL. In 2000 the Cerro Grande Fire destroyed hundreds of homes, as well as structures and equipment at the DARHT facility. The DARHT accelerators were safe in a fire-proof building. In 2011 the Las Conchas Fire burned about 630 square kilometers (250 square miles) and came dangerously close to Los Alamos/LANL. LANSCE accelerator operations Lessons Learned during Las Conchas fire: (1) Develop a plan to efficiently shut down the accelerator on short notice; (2) Establish clear lines of communication in emergencymore » situations; and (3) Plan recovery and keep squirrels out.« less
Optimization methodology for the global 10 Hz orbit feedback in RHIC
DOE Office of Scientific and Technical Information (OSTI.GOV)
Liu, Chuyu; Hulsart, R.; Mernick, K.
To combat beam oscillations induced by triplet vibrations at the Relativistic Heavy Ion Collider (RHIC), a global orbit feedback system was developed and applied at injection and top energy in 2011, and during beam acceleration in 2012. Singular Value Decomposition (SVD) was employed to determine the strengths and currents of the applied corrections. The feedback algorithm was optimized for different magnetic configurations (lattices) at fixed beam energies and during beam acceleration. While the orbit feedback performed well since its inception, corrector current transients and feedback-induced beam oscillations were observed during the polarized proton program in 2015. In this paper, wemore » present the feedback algorithm, the optimization of the algorithm for various lattices and the solution adopted to mitigate the observed current transients during beam acceleration.« less
Optimization methodology for the global 10 Hz orbit feedback in RHIC
Liu, Chuyu; Hulsart, R.; Mernick, K.; ...
2018-05-08
To combat beam oscillations induced by triplet vibrations at the Relativistic Heavy Ion Collider (RHIC), a global orbit feedback system was developed and applied at injection and top energy in 2011, and during beam acceleration in 2012. Singular Value Decomposition (SVD) was employed to determine the strengths and currents of the applied corrections. The feedback algorithm was optimized for different magnetic configurations (lattices) at fixed beam energies and during beam acceleration. While the orbit feedback performed well since its inception, corrector current transients and feedback-induced beam oscillations were observed during the polarized proton program in 2015. In this paper, wemore » present the feedback algorithm, the optimization of the algorithm for various lattices and the solution adopted to mitigate the observed current transients during beam acceleration.« less
Operator control systems and methods for swing-free gantry-style cranes
Feddema, John T.; Petterson, Ben J.; Robinett, III, Rush D.
1998-01-01
A system and method for eliminating swing motions in gantry-style cranes while subject to operator control is presented. The present invention comprises an infinite impulse response ("IIR") filter and a proportional-integral ("PI") feedback controller (50). The IIR filter receives input signals (46) (commanded velocity or acceleration) from an operator input device (45) and transforms them into output signals (47) in such a fashion that the resulting motion is swing free (i.e., end-point swinging prevented). The parameters of the IIR filter are updated in real time using measurements from a hoist cable length encoder (25). The PI feedback controller compensates for modeling errors and external disturbances, such as wind or perturbations caused by collision with objects. The PI feedback controller operates on cable swing angle measurements provided by a cable angle sensor (27). The present invention adjusts acceleration and deceleration to eliminate oscillations. An especially important feature of the present invention is that it compensates for variable-length cable motions from multiple cables attached to a suspended payload.
An evaluation of the feedback loops in the poverty focus of world bank operations.
Fardoust, Shahrokh; Kanbur, Ravi; Luo, Xubei; Sundberg, Mark
2018-04-01
The World Bank Group in 2013 made the elimination of extreme poverty by 2030 a central institutional focus and purpose. This paper, based on an evaluation conducted by the Independent Evaluation Group of the World Bank Group, examines how, and how well, the Bank uses feedback loops to enhance the poverty focus of its operations. Feedback loops are important for every element of the results chain running from data, to diagnostics, to strategy formulation and finally to strategy implementation. The evaluation uses a range of instruments, including surveys of stakeholders and World Bank staff, focus group meetings, country case studies and systematic reviews of Bank lending and non-lending operations. We find that while the Bank generates useful information on poverty reduction from its projects and programs, the feedback loops - from outcomes to data analysis to diagnostics to strategy formulation and implementation - have generally been weak, with sizable variation across countries. Copyright © 2017 The World Bank. Published by Elsevier Ltd.. All rights reserved.
Particle Accelerator Focus Automation
NASA Astrophysics Data System (ADS)
Lopes, José; Rocha, Jorge; Redondo, Luís; Cruz, João
2017-08-01
The Laboratório de Aceleradores e Tecnologias de Radiação (LATR) at the Campus Tecnológico e Nuclear, of Instituto Superior Técnico (IST) has a horizontal electrostatic particle accelerator based on the Van de Graaff machine which is used for research in the area of material characterization. This machine produces alfa (He+) and proton (H+) beams of some μA currents up to 2 MeV/q energies. Beam focusing is obtained using a cylindrical lens of the Einzel type, assembled near the high voltage terminal. This paper describes the developed system that automatically focuses the ion beam, using a personal computer running the LabVIEW software, a multifunction input/output board and signal conditioning circuits. The focusing procedure consists of a scanning method to find the lens bias voltage which maximizes the beam current measured on a beam stopper target, which is used as feedback for the scanning cycle. This system, as part of a wider start up and shut down automation system built for this particle accelerator, brings great advantages to the operation of the accelerator by turning it faster and easier to operate, requiring less human presence, and adding the possibility of total remote control in safe conditions.
Operating wind turbines in strong wind conditions by using feedforward-feedback control
NASA Astrophysics Data System (ADS)
Feng, Ju; Sheng, Wen Zhong
2014-12-01
Due to the increasing penetration of wind energy into power systems, it becomes critical to reduce the impact of wind energy on the stability and reliability of the overall power system. In precedent works, Shen and his co-workers developed a re-designed operation schema to run wind turbines in strong wind conditions based on optimization method and standard PI feedback control, which can prevent the typical shutdowns of wind turbines when reaching the cut-out wind speed. In this paper, a new control strategy combing the standard PI feedback control with feedforward controls using the optimization results is investigated for the operation of variable-speed pitch-regulated wind turbines in strong wind conditions. It is shown that the developed control strategy is capable of smoothening the power output of wind turbine and avoiding its sudden showdown at high wind speeds without worsening the loads on rotor and blades.
Network acceleration techniques
NASA Technical Reports Server (NTRS)
Crowley, Patricia (Inventor); Maccabe, Arthur Barney (Inventor); Awrach, James Michael (Inventor)
2012-01-01
Splintered offloading techniques with receive batch processing are described for network acceleration. Such techniques offload specific functionality to a NIC while maintaining the bulk of the protocol processing in the host operating system ("OS"). The resulting protocol implementation allows the application to bypass the protocol processing of the received data. Such can be accomplished this by moving data from the NIC directly to the application through direct memory access ("DMA") and batch processing the receive headers in the host OS when the host OS is interrupted to perform other work. Batch processing receive headers allows the data path to be separated from the control path. Unlike operating system bypass, however, the operating system still fully manages the network resource and has relevant feedback about traffic and flows. Embodiments of the present disclosure can therefore address the challenges of networks with extreme bandwidth delay products (BWDP).
Optimized operation of dielectric laser accelerators: Single bunch
NASA Astrophysics Data System (ADS)
Hanuka, Adi; Schächter, Levi
2018-05-01
We introduce a general approach to determine the optimal charge, efficiency and gradient for laser driven accelerators in a self-consistent way. We propose a way to enhance the operational gradient of dielectric laser accelerators by leverage of beam-loading effect. While the latter may be detrimental from the perspective of the effective gradient experienced by the particles, it can be beneficial as the effective field experienced by the accelerating structure, is weaker. As a result, the constraint imposed by the damage threshold fluence is accordingly weakened and our self-consistent approach predicts permissible gradients of ˜10 GV /m , one order of magnitude higher than previously reported experimental results—with unbunched pulse of electrons. Our approach leads to maximum efficiency to occur for higher gradients as compared with a scenario in which the beam-loading effect on the material is ignored. In any case, maximum gradient does not occur for the same conditions that maximum efficiency does—a trade-off set of parameters is suggested.
Guo, Jin; Guo, Shuxiang; Tamiya, Takashi; Hirata, Hideyuki; Ishihara, Hidenori
2016-03-01
An Internet-based tele-operative robotic catheter operating system was designed for vascular interventional surgery, to afford unskilled surgeons the opportunity to learn basic catheter/guidewire skills, while allowing experienced physicians to perform surgeries cooperatively. Remote surgical procedures, limited by variable transmission times for visual feedback, have been associated with deterioration in operability and vascular wall damage during surgery. At the patient's location, the catheter shape/position was detected in real time and converted into three-dimensional coordinates in a world coordinate system. At the operation location, the catheter shape was reconstructed in a virtual-reality environment, based on the coordinates received. The data volume reduction significantly reduced visual feedback transmission times. Remote transmission experiments, conducted over inter-country distances, demonstrated the improved performance of the proposed prototype. The maximum error for the catheter shape reconstruction was 0.93 mm and the transmission time was reduced considerably. The results were positive and demonstrate the feasibility of remote surgery using conventional network infrastructures. Copyright © 2015 John Wiley & Sons, Ltd.
Accelerator/Experiment Operations - FY 2016
DOE Office of Scientific and Technical Information (OSTI.GOV)
Blake, A.; Convery, M.; Geer, S.
2016-10-01
This Technical Memorandum summarizes the Fermilab accelerator and experiment operations for FY 2016. It is one of a series of annual publications intended to gather information in one place. In this case, the information concerns the FY 2016 NOvA, MINOS+ and MINERvA experiments using the Main Injector Neutrino Beam (NuMI), the MicroBooNE experiment and the activities in the SciBooNE Hall using the Booster Neutrino Beam (BNB), and the SeaQuest experiment, LArIAT experiment and Meson Test Beam activities in the 120 GeV external switchyard beam (SY120). Each section was prepared by the relevant authors, and was then edited for inclusion inmore » this summary.« less
Operation and reactivity measurements of an accelerator driven subcritical TRIGA reactor
NASA Astrophysics Data System (ADS)
O'Kelly, David Sean
Experiments were performed at the Nuclear Engineering Teaching Laboratory (NETL) in 2005 and 2006 in which a 20 MeV linear electron accelerator operating as a photoneutron source was coupled to the TRIGA (Training, Research, Isotope production, General Atomics) Mark II research reactor at the University of Texas at Austin (UT) to simulate the operation and characteristics of a full-scale accelerator driven subcritical system (ADSS). The experimental program provided a relatively low-cost substitute for the higher power and complexity of internationally proposed systems utilizing proton accelerators and spallation neutron sources for an advanced ADSS that may be used for the burning of high-level radioactive waste. Various instrumentation methods that permitted ADSS neutron flux monitoring in high gamma radiation fields were successfully explored and the data was used to evaluate the Stochastic Pulsed Feynman method for reactivity monitoring.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ueno, A., E-mail: akira.ueno@j-parc.jp; Ohkoshi, K.; Ikegami, K.
2015-04-08
In order to satisfy the Japan Proton Accelerator Research Complex (J-PARC) second stage requirements of an H{sup −} ion beam of 60mA within normalized emittances of 1.5πmm•mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500μs×25Hz) and a life-time of longer than 1month, the J-PARC cesiated RF-driven H{sup −} ion source was developed by using an internal-antenna developed at the Spallation Neutron Source (SNS). The maintenance and operation procedure to minimize the plasma chamber (PCH) replacement time on the beam line, which is very important to maximize the J-PARC beam time especially for an antenna failure,more » is presented in this paper. The PCH preserved by filling argon (Ar) gas inside after pre-conditioning including pre-cesiation to produce the required beam at a test-stand successfully produced the required beam on the beam line with slight addition of cesium (Cs). The methods of the feedback controls of a 2MHz-RF-matching, an H{sup −} ion beam intensity and the addition of Cs are also presented. The RF-matching feedback by using two vacuum variable capacitors (VVCs) and RF-frequency shift produced the almost perfect matching with negligibly small reflected RF-power. The H{sup −} ion beam intensity was controlled within errors of ±0.1mA by the RF-power feedback. The amount of Cs was also controlled by remotely opening a Cs-valve to keep the RF-power lower than a settled value.« less
A Current-Mode Common-Mode Feedback Circuit (CMFB) with Rail-to-Rail Operation
NASA Astrophysics Data System (ADS)
Suadet, Apirak; Kasemsuwan, Varakorn
2011-03-01
This paper presents a current-mode common-mode feedback (CMFB) circuit with rail-to-rail operation. The CMFB is a stand-alone circuit, which can be connected to any low voltage transconductor without changing or upsetting the existing circuit. The proposed CMFB employs current mirrors, operating as common-mode detector and current amplifier to enhance the loop gain of the CMFB. The circuit employs positive feedback to enhance the output impedance and gain. The circuit has been designed using a 0.18
Reliability Considerations for the Operation of Large Accelerator User Facilities
Willeke, F. J.
2016-01-29
The lecture provides an overview of considerations relevant for achieving highly reliable operation of accelerator based user facilities. The article starts with an overview of statistical reliability formalism which is followed by high reliability design considerations with examples. Finally, the article closes with operational aspects of high reliability such as preventive maintenance and spares inventory.
Characteristics of a 30-cm thruster operated with small hole accelerator grid ion optics
NASA Technical Reports Server (NTRS)
Vahrenkamp, R. P.
1976-01-01
Small hole accelerator grid ion optical systems have been tested as a possible means of improving 30-cm ion thruster performance. The effects of small hole grids on the critical aspects of thruster operation including discharge chamber performance, doubly-charged ion concentration, effluent beam characteristics, and plasma properties have been evaluated. In general, small hole accelerator grids are beneficial in improving thruster performance while maintaining low double ion ratios. However, extremely small accelerator aperture diameters tend to degrade beam divergence characteristics. A quantitative discussion of these advantages and disadvantages of small hole accelerator grids, as well as resulting variations in thruster operation characteristics, is presented.
Choosing order of operations to accelerate strip structure analysis in parameter range
NASA Astrophysics Data System (ADS)
Kuksenko, S. P.; Akhunov, R. R.; Gazizov, T. R.
2018-05-01
The paper considers the issue of using iteration methods in solving the sequence of linear algebraic systems obtained in quasistatic analysis of strip structures with the method of moments. Using the analysis of 4 strip structures, the authors have proved that additional acceleration (up to 2.21 times) of the iterative process can be obtained during the process of solving linear systems repeatedly by means of choosing a proper order of operations and a preconditioner. The obtained results can be used to accelerate the process of computer-aided design of various strip structures. The choice of the order of operations to accelerate the process is quite simple, universal and could be used not only for strip structure analysis but also for a wide range of computational problems.
Ignition feedback regenerative free electron laser (FEL) amplifier
Kim, Kwang-Je; Zholents, Alexander; Zolotorev, Max
2001-01-01
An ignition feedback regenerative amplifier consists of an injector, a linear accelerator with energy recovery, and a high-gain free electron laser amplifier. A fraction of the free electron laser output is coupled to the input to operate the free electron laser in the regenerative mode. A mode filter in this loop prevents run away instability. Another fraction of the output, after suitable frequency up conversion, is used to drive the photocathode. An external laser is provided to start up both the amplifier and the injector, thus igniting the system.
SEE induced in SRAM operating in a superconducting electron linear accelerator environment
NASA Astrophysics Data System (ADS)
Makowski, D.; Mukherjee, Bhaskar; Grecki, M.; Simrock, Stefan
2005-02-01
Strong fields of bremsstrahlung photons and photoneutrons are produced during the operation of high-energy electron linacs. Therefore, a mixed gamma and neutron radiation field dominates the accelerators environment. The gamma radiation induced Total Ionizing Dose (TID) effect manifests the long-term deterioration of the electronic devices operating in accelerator environment. On the other hand, the neutron radiation is responsible for Single Event Effects (SEE) and may cause a temporal loss of functionality of electronic systems. This phenomenon is known as Single Event Upset (SEU). The neutron dose (KERMA) was used to scale the neutron induced SEU in the SRAM chips. Hence, in order to estimate the neutron KERMA conversion factor for Silicon (Si), dedicated calibration experiments using an Americium-Beryllium (241Am/Be) neutron standard source was carried out. Single Event Upset (SEU) influences the short-term operation of SRAM compared to the gamma induced TID effect. We are at present investigating the feasibility of an SRAM based real-time beam-loss monitor for high-energy accelerators utilizing the SEU caused by fast neutrons. This paper highlights the effects of gamma and neutron radiations on Static Random Access Memory (SRAM), placed at selected locations near the Superconducting Linear Accelerator driving the Vacuum UV Free Electron Laser (VUVFEL) of DESY.
Operational Assessment of Tools for Accelerating Leader Development (ALD): Volume 2, Appendices
2009-06-01
Qual Qualitative Quant Quantitative RC Reserve Component R&D Research and Development re: reference reqts requirements ROTC Reserve Officer...part in the Accelerating Leader Development program, please complete the Pretest , Training, and Posttest . Of course, you may complete the longer...ARI Research Note 2009-09 Operational Assessment of Tools for Accelerating Leader Development (ALD): Volume II, Appendices Bruce
Next Generation Environmentally-Friendly Driving Feedback Systems Research and Development
DOE Office of Scientific and Technical Information (OSTI.GOV)
Barth, Matthew; Boriboonsomsin, Kanok
2014-12-31
used for paratransit service. Detailed vehicle travel and operation data including route taken, driving speed, acceleration, braking, and the corresponding fuel consumption, were collected both before and during the test period. The data analysis results show that the fleet average fuel efficiency improvements for the three fleets with the use of the driving feedback system are in the range of 2% to 9%. The economic viability of the driving feedback system is high. A fully deployed system would require capital investment in smart device ($150-$350) and on-board diagnostics connector ($50-$100) as well as paying operating costs for wireless data plan and subscription fees ($20-$30 per month) for connecting to the data server and receiving various system services. For individual consumers who already own a smart device (such as smartphone) and commercial fleets that already use some kind of telematics services, the costs for deploying this driving feedback system would be much lower.« less
Operational Assessment of Tools for Accelerating Leader Development (ALD): Volume 1, Capstone Report
2009-06-01
in units and user juries provided feedback on the tools. The pressures of the operational environment seriously limited the time available to work...following functions: account set-up, user authentication, learning management , usage monitoring, problem reporting, assessment data collection, data...especially sources of data) represented—demonstration/assessment manager , operations manager , Web site experts, users (target audience), data collectors
Nonlinear feedback guidance law for aero-assisted orbit transfer maneuvers
NASA Technical Reports Server (NTRS)
Menon, P. K. A.
1992-01-01
Aero-assisted orbit transfer vehicles have the potential for significantly reducing the fuel requirements in certain classes of orbit transfer operations. Development of a nonlinear feedback guidance law for performing aero-assisted maneuvers that accomplish simultaneous change of all the orbital elements with least vehicle acceleration magnitude is discussed. The analysis is based on a sixth order nonlinear point-mass vehicle model with lift, bank angle, thrust and drag modulation as the control variables. The guidance law uses detailed vehicle aerodynamic and the atmosphere models in the feedback loop. Higher-order gravitational harmonics, planetary atmosphere rotation and ambient winds are included in the formulation. Due to modest computational requirements, the guidance law is implementable on-board an orbit transfer vehicle. The guidance performance is illustrated for three sets of boundary conditions.
An efficient magnetron transmitter for superconducting accelerators
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kazakevich, G.; Lebedev, V.; Yakovlev, V.
A concept of a highly-efficient high-power magnetron transmitter allowing wide-band phase and the mid-frequency power control at the frequency of the locking signal is proposed. The proposal is aimed for powering Superconducting RF (SRF) cavities of intensity-frontier accelerators. The transmitter is intended to operate with phase and amplitude control feedback loops allowing suppression of microphonics and beam loading in the SRF cavities. The concept utilizes injectionlocked magnetrons controlled in phase by the locking signal supplied by a feedback system. The injection-locking signal pre-excites the magnetron and allows its operation below the critical voltage. This realizes control of the magnetron powermore » in a wide range by control of the magnetron current. Pre-excitation of the magnetron by the locking signal provides an output power range up to 10 dB. Experimental studies were carried out with 2.45 GHz, 1 kW, CW magnetrons. They demonstrated stable operation of the magnetrons and power control at a low noise level. In conclusion, an analysis of the kinetics of the drifting charge in the drift approximation substantiates the concept and the experimental results.« less
An efficient magnetron transmitter for superconducting accelerators
Kazakevich, G.; Lebedev, V.; Yakovlev, V.; ...
2016-09-22
A concept of a highly-efficient high-power magnetron transmitter allowing wide-band phase and the mid-frequency power control at the frequency of the locking signal is proposed. The proposal is aimed for powering Superconducting RF (SRF) cavities of intensity-frontier accelerators. The transmitter is intended to operate with phase and amplitude control feedback loops allowing suppression of microphonics and beam loading in the SRF cavities. The concept utilizes injectionlocked magnetrons controlled in phase by the locking signal supplied by a feedback system. The injection-locking signal pre-excites the magnetron and allows its operation below the critical voltage. This realizes control of the magnetron powermore » in a wide range by control of the magnetron current. Pre-excitation of the magnetron by the locking signal provides an output power range up to 10 dB. Experimental studies were carried out with 2.45 GHz, 1 kW, CW magnetrons. They demonstrated stable operation of the magnetrons and power control at a low noise level. In conclusion, an analysis of the kinetics of the drifting charge in the drift approximation substantiates the concept and the experimental results.« less
Feedback-assisted extension of the tokamak operating space to low safety factor
Hanson, Jeremy M.; Bialek, James M.; Baruzzo, M.; ...
2014-07-07
Recent DIII-D and RFX-mod experiments have demonstrated stable tokamak operation at very low values of the edge safety factor q( a) near and below 2. The onset of n = 1 resistive wall mode (RWM) kink instabilities leads to a disruptive stability limit, encountered at q( a) = 2 (limiter plasmas) and q 95 = 2 (divertor plasmas). However, passively stable operation can be attained for q( a) and q 95 values as low as 2.2. RWM damping in the q( a) = 2 regime was measured using active MHD spectroscopy. Although consistent with theoretical predictions, the amplitude of themore » damped response does not increase significantly as the q( a) = 2 limit is approached, in contrast with damping measurements made approaching the pressure-driven RWM limit. Applying proportional gain magnetic feedback control of the n = 1 modes has resulted in stabilized operation with q 95 values reaching as low as 1.9 in DIII-D and q( a) reaching 1.55 in RFX-mod. In addition to being consistent with the q( a) = 2 external kink mode stability limit, the unstable modes have growth rates on the order of the characteristic wall eddy-current decay timescale in both devices, and a dominant m = 2 poloidal structure that is consistent with ideal MHD predictions. As a result, the experiments contribute to validating MHD stability theory and demonstrate that a key tokamak stability limit can be overcome with feedback.« less
Prsa, Mario; Galiñanes, Gregorio L; Huber, Daniel
2017-02-22
Neuronal motor commands, whether generating real or neuroprosthetic movements, are shaped by ongoing sensory feedback from the displacement being produced. Here we asked if cortical stimulation could provide artificial feedback during operant conditioning of cortical neurons. Simultaneous two-photon imaging and real-time optogenetic stimulation were used to train mice to activate a single neuron in motor cortex (M1), while continuous feedback of its activity level was provided by proportionally stimulating somatosensory cortex. This artificial signal was necessary to rapidly learn to increase the conditioned activity, detect correct performance, and maintain the learned behavior. Population imaging in M1 revealed that learning-related activity changes are observed in the conditioned cell only, which highlights the functional potential of individual neurons in the neocortex. Our findings demonstrate the capacity of animals to use an artificially induced cortical channel in a behaviorally relevant way and reveal the remarkable speed and specificity at which this can occur. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.
A prototype of a beam steering assistant tool for accelerator operations
DOE Office of Scientific and Technical Information (OSTI.GOV)
M. Bickley; P. Chevtsov
2006-10-24
The CEBAF accelerator provides nuclear physics experiments at Jefferson Lab with high quality electron beams. Three experimental end stations can simultaneously receive the beams with different energies and intensities. For each operational mode, the accelerator setup procedures are complicated and require very careful checking of beam spot sizes and positions on multiple beam viewers. To simplify these procedures and make them reproducible, a beam steering assistant GUI tool has been created. The tool is implemented as a multi-window control screen. The screen has an interactive graphical object window, which is an overlay on top of a digitized live video imagemore » from a beam viewer. It allows a user to easily create and edit any graphical objects consisting of text, ellipses, and lines, right above the live beam viewer image and then save them in a file that is called a beam steering template. The template can show, for example, the area within which the beam must always be on the viewer. Later, this template can be loaded in the interactive graphical object window to help accelerator operators steer the beam to the specified area on the viewer.« less
Fundamental Principles of Coherent-Feedback Quantum Control
2014-12-08
in metrology (acceleration sensing, vibrometry, gravity wave detection) and in quantum information processing (continuous-variables quantum ...AFRL-OSR-VA-TR-2015-0009 FUNDAMENTAL PRINCIPLES OF COHERENT-FEEDBACK QUANTUM CONTROL Hideo Mabuchi LELAND STANFORD JUNIOR UNIV CA Final Report 12/08...foundations and potential applications of coherent-feedback quantum control. We have focused on potential applications in quantum -enhanced metrology and
Production of isometric forces during sustained acceleration.
Sand, D P; Girgenrath, M; Bock, O; Pongratz, H
2003-06-01
The operation of high-performance aircraft requires pilots to apply finely graded forces on controls. Since they are often exposed to high levels of acceleration in flight, we investigated to what extent this ability is degraded in such an environment. Twelve healthy non-pilot volunteers were seated in the gondola of a centrifuge and their performance was tested at normal gravity (1 G) and while exposed to sustained forces of 1.5 G and 3 G oriented from head to foot (+Gz). Using an isometric joystick, they attempted to produce force vectors with specific lengths and directions commanded in random order by a visual display. Acceleration had substantial effects on the magnitude of produced force. Compared with 1 G, maximum produced force was about 2 N higher at 1.5 G and about 10 N higher at 3 G. The size of this effect was constant across the different magnitudes, but varied with the direction of the prescribed force. Acceleration degrades control of force production. This finding may indicate that the motor system misinterprets the unusual gravitoinertial environment and/or that proprioceptive feedback is degraded due to increased muscle tone. The production of excessive isometric force could affect the safe operation of high-performance aircraft.
NASA Astrophysics Data System (ADS)
Mao, Xuefeng; Zhou, Xinlei; Yu, Qingxu
2016-02-01
We describe a stabilizing operation point technique based on the tunable Distributed Feedback (DFB) laser for quadrature demodulation of interferometric sensors. By introducing automatic lock quadrature point and wavelength periodically tuning compensation into an interferometric system, the operation point of interferometric system is stabilized when the system suffers various environmental perturbations. To demonstrate the feasibility of this stabilizing operation point technique, experiments have been performed using a tunable-DFB-laser as light source to interrogate an extrinsic Fabry-Perot interferometric vibration sensor and a diaphragm-based acoustic sensor. Experimental results show that good tracing of Q-point was effectively realized.
Effects of acoustic feedback training in elite-standard Para-Rowing.
Schaffert, Nina; Mattes, Klaus
2015-01-01
Assessment and feedback devices have been regularly used in technique training in high-performance sports. Biomechanical analysis is mainly visually based and so can exclude athletes with visual impairments. The aim of this study was to examine the effects of auditory feedback on mean boat speed during on-water training of visually impaired athletes. The German National Para-Rowing team (six athletes, mean ± s, age 34.8 ± 10.6 years, body mass 76.5 ± 13.5 kg, stature 179.3 ± 8.6 cm) participated in the study. Kinematics included boat acceleration and distance travelled, collected with Sofirow at two intensities of training. The boat acceleration-time traces were converted online into acoustic feedback and presented via speakers during rowing (sections with and without alternately). Repeated-measures within-participant factorial ANOVA showed greater boat speed with acoustic feedback than baseline (0.08 ± 0.01 m·s(-1)). The time structure of rowing cycles was improved (extended time of positive acceleration). Questioning of athletes showed acoustic feedback to be a supportive training aid as it provided important functional information about the boat motion independent of vision. It gave access for visually impaired athletes to biomechanical analysis via auditory information. The concept for adaptive athletes has been successfully integrated into the preparation for the Para-Rowing World Championships and Paralympics.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Green, O; Mutic, S; Li, H
2016-06-15
Purpose: To describe the performance of a linear accelerator operating in a compact MRI-guided radiation therapy system. Methods: A commercial linear accelerator was placed in an MRI unit that is employed in a commercial MR-based image guided radiation therapy (IGRT) system. The linear accelerator components were placed within magnetic field-reducing hardware that provided magnetic fields of less than 40 G for the magnetron, gun driver, and port circulator, with 1 G for the linear accelerator. The system did not employ a flattening filter. The test linear accelerator was an industrial 4 MV model that was employed to test the abilitymore » to run an accelerator in the MR environment. An MR-compatible diode detector array was used to measure the beam profiles with the accelerator outside and inside the MR field and with the gradient coils on and off to examine if there was any effect on the delivered dose distribution. The beam profiles and time characteristics of the beam were measured. Results: The beam profiles exhibited characteristic unflattened Bremsstrahlung features with less than ±1.5% differences in the profile magnitude when the system was outside and inside the magnet and less than 1% differences with the gradient coils on and off. The central axis dose rate fluctuated by less than 1% over a 30 second period when outside and inside the MRI. Conclusion: A linaccompatible MR design has been shown to be effective in not perturbing the operation of a commercial linear accelerator. While the accelerator used in the tests was 4MV, there is nothing fundamentally different with the operation of a 6MV unit, implying that the design will enable operation of the proposed clinical unit. Research funding provided by ViewRay, Inc.« less
Iowa Acceleration Scale Manual: A Guide for Whole-Grade Acceleration K-8. (3rd Edition, Manual)
ERIC Educational Resources Information Center
Assouline, Susan G.; Colangelo, Nicholas; Lupkowski-Shoplik, Ann; Forstadt, Leslie; Lipscomb, Jonathon
2009-01-01
Feedback from years of nationwide use has resulted in a 3rd Edition of this unique, systematic, and objective guide to considering and implementing academic acceleration. Developed and tested by the Belin-Blank Center at the University of Iowa, the IAS ensures that acceleration decisions are systematic, thoughtful, well reasoned, and defensible.…
Adaptive control for accelerators
Eaton, Lawrie E.; Jachim, Stephen P.; Natter, Eckard F.
1991-01-01
An adaptive feedforward control loop is provided to stabilize accelerator beam loading of the radio frequency field in an accelerator cavity during successive pulses of the beam into the cavity. A digital signal processor enables an adaptive algorithm to generate a feedforward error correcting signal functionally determined by the feedback error obtained by a beam pulse loading the cavity after the previous correcting signal was applied to the cavity. Each cavity feedforward correcting signal is successively stored in the digital processor and modified by the feedback error resulting from its application to generate the next feedforward error correcting signal. A feedforward error correcting signal is generated by the digital processor in advance of the beam pulse to enable a composite correcting signal and the beam pulse to arrive concurrently at the cavity.
Does Mechanism Matter? Student Recall of Electronic versus Handwritten Feedback
ERIC Educational Resources Information Center
Osterbur, Megan E.; Hammer, Elizabeth Yost; Hammer, Elliott
2015-01-01
Student consumption and recall of feedback are necessary preconditions of successful formative assessment. Drawing on Sadler's (1998) definition of formative assessment as that which is intended to accelerate learning and improve performance through the providing of feedback, we examine how the mechanism of transmission may impact student…
Performance evaluation of a robot-assisted catheter operating system with haptic feedback.
Song, Yu; Guo, Shuxiang; Yin, Xuanchun; Zhang, Linshuai; Hirata, Hideyuki; Ishihara, Hidenori; Tamiya, Takashi
2018-06-20
In this paper, a novel robot-assisted catheter operating system (RCOS) has been proposed as a method to reduce physical stress and X-ray exposure time to physicians during endovascular procedures. The unique design of this system allows the physician to apply conventional bedside catheterization skills (advance, retreat and rotate) to an input catheter, which is placed at the master side to control another patient catheter placed at the slave side. For this purpose, a magnetorheological (MR) fluids-based master haptic interface has been developed to measure the axial and radial motions of an input catheter, as well as to provide the haptic feedback to the physician during the operation. In order to achieve a quick response of the haptic force in the master haptic interface, a hall sensor-based closed-loop control strategy is employed. In slave side, a catheter manipulator is presented to deliver the patient catheter, according to position commands received from the master haptic interface. The contact forces between the patient catheter and blood vessel system can be measured by designed force sensor unit of catheter manipulator. Four levels of haptic force are provided to make the operator aware of the resistance encountered by the patient catheter during the insertion procedure. The catheter manipulator was evaluated for precision positioning. The time lag from the sensed motion to replicated motion is tested. To verify the efficacy of the proposed haptic feedback method, the evaluation experiments in vitro are carried out. The results demonstrate that the proposed system has the ability to enable decreasing the contact forces between the catheter and vasculature.
Exploratory Evaluation of Audio Email Technology in Formative Assessment Feedback
ERIC Educational Resources Information Center
Macgregor, George; Spiers, Alex; Taylor, Chris
2011-01-01
Formative assessment generates feedback on students' performance, thereby accelerating and improving student learning. Anecdotal evidence gathered by a number of evaluations has hypothesised that audio feedback may be capable of enhancing student learning more than other approaches. In this paper we report on the preliminary findings of a…
Operations and maintenance manual for the linear accelerator (sled)
NASA Technical Reports Server (NTRS)
1981-01-01
The Linear Accelerator, a sliding chair which is pulled along a stationary platform in a horizontal axis is described. The driving force is a motor controlled by a velocity loop amplifier, and the mechanical link to the chair is a steel cable. The chair is moved in forward and reverse directions as indicated by the direction of motor rotation. The system operation is described with emphasis on the electronic control and monitoring functions. Line-by-line schematics and wire lists are included.
NASA Technical Reports Server (NTRS)
Delombard, Richard; Finley, Brian D.
1991-01-01
The Space Acceleration Measurement System (SAMS) project and flight units are briefly described. The SAMS operations during the STS-40 mission are summarized, and a preliminary look at some of the acceleration data from that mission are provided. The background and rationale for the SAMS project is described to better illustrate its goals. The functions and capabilities of each SAMS flight unit are first explained, then the STS-40 mission, the SAMS's function for that mission, and the preparation of the SAMS are described. Observations about the SAMS operations during the first SAMS mission are then discussed. Some sample data are presented illustrating several aspects of the mission's microgravity environment.
Achievement of radiative feedback control for long-pulse operation on EAST
NASA Astrophysics Data System (ADS)
Wu, K.; Yuan, Q. P.; Xiao, B. J.; Wang, L.; Duan, Y. M.; Chen, J. B.; Zheng, X. W.; Liu, X. J.; Zhang, B.; Xu, J. C.; Luo, Z. P.; Zang, Q.; Li, Y. Y.; Feng, W.; Wu, J. H.; Yang, Z. S.; Zhang, L.; Luo, G.-N.; Gong, X. Z.; Hu, L. Q.; Hu, J. S.; Li, J.
2018-05-01
The active feedback control of radiated power to prevent divertor target plates overheating during long-pulse operation has been developed and implemented on EAST. The radiation control algorithm, with impurity seeding via a supersonic molecular beam injection (SMBI) system, has shown great success in both reliability and stability. By seeding a sequence of short neon (Ne) impurity pulses with the SMBI from the outer mid-plane, the radiated power of the bulk plasma can be well controlled, and the duration of radiative control (feedforward and feedback) is 4.5 s during a discharge of 10 s. Reliable control of the total radiated power of bulk plasma has been successfully achieved in long-pulse upper single null (USN) discharges with a tungsten divertor. The achieved control range of {{f}rad} is 20%–30% in L-mode regimes and 18%–36% in H-mode regimes. The temperature of the divertor target plates was maintained at a low level during the radiative control phase. The peak particle flux on the divertor target was decreased by feedforward Ne injection in the L-mode discharges, while the Ne pulses from the SMBI had no influence on the peak particle flux because of the very small injecting volume. It is shown that although the radiated power increased, no serious reduction of plasma-stored energy or confinement was observed during the control phase. The success of the radiation control algorithm and current experiments in radiated power control represents a significant advance for steady-state divertor radiation and heat flux control on EAST for near-future long-pulse operation.
Mitigating driver distraction with retrospective and concurrent feedback.
Donmez, Birsen; Boyle, Linda Ng; Lee, John D
2008-03-01
An experiment was conducted to assess the effects of retrospective and combined retrospective and concurrent feedback on driver performance and engagement in distracting activities. A previous study conducted by the authors showed that concurrent (or real time) feedback can help drivers better modulate their distracting activities. However, research also shows that concurrent feedback can pose additional distractions due to the limited time and resources available during driving. Retrospective feedback, which is presented at the end of a trip (i.e., post-drive), can include additional information on safety critical situations during a trip and help the driver learn safe driving habits. A driving simulator study was conducted with 48 participants and 3 conditions: retrospective feedback, combined feedback (both retrospective and concurrent), and no feedback (baseline case). The feedback conditions (retrospective and combined) resulted in faster response to lead vehicle braking events as depicted by shorter accelerator release times. Moreover, combined feedback also resulted in longer glances to the road. The results suggest that both feedback types have potential to improve immediate driving performance and driver engagement in distractions. Combined feedback holds the most promise for mitigating the effects of distraction from in-vehicle information systems.
Permafrost carbon-climate feedbacks accelerate global warming.
Koven, Charles D; Ringeval, Bruno; Friedlingstein, Pierre; Ciais, Philippe; Cadule, Patricia; Khvorostyanov, Dmitry; Krinner, Gerhard; Tarnocai, Charles
2011-09-06
Permafrost soils contain enormous amounts of organic carbon, which could act as a positive feedback to global climate change due to enhanced respiration rates with warming. We have used a terrestrial ecosystem model that includes permafrost carbon dynamics, inhibition of respiration in frozen soil layers, vertical mixing of soil carbon from surface to permafrost layers, and CH(4) emissions from flooded areas, and which better matches new circumpolar inventories of soil carbon stocks, to explore the potential for carbon-climate feedbacks at high latitudes. Contrary to model results for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4), when permafrost processes are included, terrestrial ecosystems north of 60°N could shift from being a sink to a source of CO(2) by the end of the 21st century when forced by a Special Report on Emissions Scenarios (SRES) A2 climate change scenario. Between 1860 and 2100, the model response to combined CO(2) fertilization and climate change changes from a sink of 68 Pg to a 27 + -7 Pg sink to 4 + -18 Pg source, depending on the processes and parameter values used. The integrated change in carbon due to climate change shifts from near zero, which is within the range of previous model estimates, to a climate-induced loss of carbon by ecosystems in the range of 25 + -3 to 85 + -16 Pg C, depending on processes included in the model, with a best estimate of a 62 + -7 Pg C loss. Methane emissions from high-latitude regions are calculated to increase from 34 Tg CH(4)/y to 41-70 Tg CH(4)/y, with increases due to CO(2) fertilization, permafrost thaw, and warming-induced increased CH(4) flux densities partially offset by a reduction in wetland extent.
Interface Prostheses With Classifier-Feedback-Based User Training.
Fang, Yinfeng; Zhou, Dalin; Li, Kairu; Liu, Honghai
2017-11-01
It is evident that user training significantly affects performance of pattern-recognition-based myoelectric prosthetic device control. Despite plausible classification accuracy on offline datasets, online accuracy usually suffers from the changes in physiological conditions and electrode displacement. The user ability in generating consistent electromyographic (EMG) patterns can be enhanced via proper user training strategies in order to improve online performance. This study proposes a clustering-feedback strategy that provides real-time feedback to users by means of a visualized online EMG signal input as well as the centroids of the training samples, whose dimensionality is reduced to minimal number by dimension reduction. Clustering feedback provides a criterion that guides users to adjust motion gestures and muscle contraction forces intentionally. The experiment results have demonstrated that hand motion recognition accuracy increases steadily along the progress of the clustering-feedback-based user training, while conventional classifier-feedback methods, i.e., label feedback, hardly achieve any improvement. The result concludes that the use of proper classifier feedback can accelerate the process of user training, and implies prosperous future for the amputees with limited or no experience in pattern-recognition-based prosthetic device manipulation.It is evident that user training significantly affects performance of pattern-recognition-based myoelectric prosthetic device control. Despite plausible classification accuracy on offline datasets, online accuracy usually suffers from the changes in physiological conditions and electrode displacement. The user ability in generating consistent electromyographic (EMG) patterns can be enhanced via proper user training strategies in order to improve online performance. This study proposes a clustering-feedback strategy that provides real-time feedback to users by means of a visualized online EMG signal input as well
Acceleration Modes and Transitions in Pulsed Plasma Accelerators
NASA Technical Reports Server (NTRS)
Polzin, Kurt A.; Greve, Christine M.
2018-01-01
Pulsed plasma accelerators typically operate by storing energy in a capacitor bank and then discharging this energy through a gas, ionizing and accelerating it through the Lorentz body force. Two plasma accelerator types employing this general scheme have typically been studied: the gas-fed pulsed plasma thruster and the quasi-steady magnetoplasmadynamic (MPD) accelerator. The gas-fed pulsed plasma accelerator is generally represented as a completely transient device discharging in approximately 1-10 microseconds. When the capacitor bank is discharged through the gas, a current sheet forms at the breech of the thruster and propagates forward under a j (current density) by B (magnetic field) body force, entraining propellant it encounters. This process is sometimes referred to as detonation-mode acceleration because the current sheet representation approximates that of a strong shock propagating through the gas. Acceleration of the initial current sheet ceases when either the current sheet reaches the end of the device and is ejected or when the current in the circuit reverses, striking a new current sheet at the breech and depriving the initial sheet of additional acceleration. In the quasi-steady MPD accelerator, the pulse is lengthened to approximately 1 millisecond or longer and maintained at an approximately constant level during discharge. The time over which the transient phenomena experienced during startup typically occur is short relative to the overall discharge time, which is now long enough for the plasma to assume a relatively steady-state configuration. The ionized gas flows through a stationary current channel in a manner that is sometimes referred to as the deflagration-mode of operation. The plasma experiences electromagnetic acceleration as it flows through the current channel towards the exit of the device. A device that had a short pulse length but appeared to operate in a plasma acceleration regime different from the gas-fed pulsed plasma
Shah, Dipali Yogesh; Dadpe, Ashwini Manish; Kalra, Dheeraj Deepak; Garcha, Vikram P
2015-12-01
The aim of this study was to investigate if a videotaped feedback method enhanced teaching and learning outcomes in a preclinical operative laboratory setting for novice learners. In 2013, 60 dental students at a dental school in India were randomly assigned to two groups: control (n=30) and experimental (n=30). The control group prepared a Class II tooth preparation for amalgam after receiving a video demonstration of the exercise. The experimental group received the same video demonstration as the control group, but they also participated in a discussion and analysis of the control groups' videotaped performance and then performed the same exercise. The self-evaluation scores (SS) and examiner evaluation scores (ES) of the two groups were compared using the unpaired t-test. The experimental group also used a five-point Likert scale to rate each item on the feedback form. The means of SS (13.65±2.43) and ES (14.75±1.97) of the experimental group were statistically higher than the means of SS (11.55±2.09) and ES (11.60±1.82) of the control group. Most students in the experimental group perceived that this technique enhanced their learning experience. Within the limits of this study, the videotaped feedback using both ideal and non-ideal examples enhanced the students' performance.
NASA Technical Reports Server (NTRS)
Engel, Jerome N.; Copp, Martin R.
1959-01-01
Acceleration, airspeed, and altitude data obtained with an NACA VGH recorder from a four-engine commercial transport airplane operating over a northwestern United States-Alaska route were evaluated to determine the magnitude and frequency of occurrence of gust and maneuver accelerations., operating airspeeds, and gust velocities. The results obtained were then compared with the results previously reported in NACA Technical Note 3475 for two similar airplanes operating over transcontinental routes in the United States. No large variations in the gust experience for the three operations were noted. The results indicate that the gust-load experience of the present operation closely approximated that of the central transcontinental route in the United States with which it is compared and showed differences of about 4 to 1 when compared with that of the southern transcontinental route in the United States. In general, accelerations due to gusts occurred much more frequently than those due to operational maneuvers. At a measured normal-acceleration increment of 0.5g, accelerations due to gusts occurred roughly 35 times more frequently than those due to operational maneuvers.
Parasitic modes removal out of operating mode neighbourhood in the DAW accelerating structure
DOE Office of Scientific and Technical Information (OSTI.GOV)
Andreev, V.G.; Belugin, V.M.; Esin, S.K.
1983-08-01
The disk and washer (DAW) accelerating structure finds its use in a number of new projects (PIGMI, SNQ etc ). It composes the main part of the accelerating structure of the meson factory now under construction in the Institute for Nuclear Research (INR), Moscow. It is known that the parasitic modes with azimuthal field variations exist at the operating mode region. In this report different methods of the parasitic modes frequency shift are considered. The main attention is given to the resonant methods, which are the most efficient.
1948-10-01
OPERATION By Walter G. Walker SUMMARY Acceleration and airspeed data taken on four Sikorsky S-42A air- planes operated on Caribbean routes and...INTRODUCTION Previous analyses (references 1 to 3) present the results obtained from acceleration and airspeed data taken during commercial transport...N.ADA TN No. 1733 This" paper gl.ves the results of’ an. analysis of’. V-G data taken on f’our Sikorsky S-42A f’ly:l.ng boats operated on Caribbean
Accelerator system and method of accelerating particles
NASA Technical Reports Server (NTRS)
Wirz, Richard E. (Inventor)
2010-01-01
An accelerator system and method that utilize dust as the primary mass flux for generating thrust are provided. The accelerator system can include an accelerator capable of operating in a self-neutralizing mode and having a discharge chamber and at least one ionizer capable of charging dust particles. The system can also include a dust particle feeder that is capable of introducing the dust particles into the accelerator. By applying a pulsed positive and negative charge voltage to the accelerator, the charged dust particles can be accelerated thereby generating thrust and neutralizing the accelerator system.
NASA Technical Reports Server (NTRS)
Macfarlane, J. J.
1992-01-01
We investigate the convergence properties of Lambda-acceleration methods for non-LTE radiative transfer problems in planar and spherical geometry. Matrix elements of the 'exact' A-operator are used to accelerate convergence to a solution in which both the radiative transfer and atomic rate equations are simultaneously satisfied. Convergence properties of two-level and multilevel atomic systems are investigated for methods using: (1) the complete Lambda-operator, and (2) the diagonal of the Lambda-operator. We find that the convergence properties for the method utilizing the complete Lambda-operator are significantly better than those of the diagonal Lambda-operator method, often reducing the number of iterations needed for convergence by a factor of between two and seven. However, the overall computational time required for large scale calculations - that is, those with many atomic levels and spatial zones - is typically a factor of a few larger for the complete Lambda-operator method, suggesting that the approach should be best applied to problems in which convergence is especially difficult.
Nonlinear dynamics of autonomous vehicles with limits on acceleration
NASA Astrophysics Data System (ADS)
Davis, L. C.
2014-07-01
The stability of autonomous vehicle platoons with limits on acceleration and deceleration is determined. If the leading-vehicle acceleration remains within the limits, all vehicles in the platoon remain within the limits when the relative-velocity feedback coefficient is equal to the headway time constant [k=1/h]. Furthermore, if the sensitivity α>1/h, no collisions occur. String stability for small perturbations is assumed and the initial condition is taken as the equilibrium state. Other values of k and α that give stability with no collisions are found from simulations. For vehicles with non-negligible mechanical response, simulations indicate that the acceleration-feedback-control gain might have to be dynamically adjusted to obtain optimal performance as the response time changes with engine speed. Stability is demonstrated for some perturbations that cause initial acceleration or deceleration greater than the limits, yet do not cause collisions.
Accelerated Reader™. What Works Clearinghouse Intervention Report. Updated
ERIC Educational Resources Information Center
What Works Clearinghouse, 2016
2016-01-01
Accelerated Reader™ is a computerized supplementary reading program that provides guided reading instruction to students in grades K-12. It aims to improve students' reading skills through reading practice and by providing frequent feedback on students' progress to teachers. The Accelerated Reader™ program requires students to select and read a…
An improved cellular automata model for train operation simulation with dynamic acceleration
NASA Astrophysics Data System (ADS)
Li, Wen-Jun; Nie, Lei
2018-03-01
Urban rail transit plays an important role in the urban public traffic because of its advantages of fast speed, large transport capacity, high safety, reliability and low pollution. This study proposes an improved cellular automaton (CA) model by considering the dynamic characteristic of the train acceleration to analyze the energy consumption and train running time. Constructing an effective model for calculating energy consumption to aid train operation improvement is the basis for studying and analyzing energy-saving measures for urban rail transit system operation.
Permafrost carbon-climate feedbacks accelerate global warming
Koven, Charles D.; Ringeval, Bruno; Friedlingstein, Pierre; Ciais, Philippe; Cadule, Patricia; Khvorostyanov, Dmitry; Krinner, Gerhard; Tarnocai, Charles
2011-01-01
Permafrost soils contain enormous amounts of organic carbon, which could act as a positive feedback to global climate change due to enhanced respiration rates with warming. We have used a terrestrial ecosystem model that includes permafrost carbon dynamics, inhibition of respiration in frozen soil layers, vertical mixing of soil carbon from surface to permafrost layers, and CH4 emissions from flooded areas, and which better matches new circumpolar inventories of soil carbon stocks, to explore the potential for carbon-climate feedbacks at high latitudes. Contrary to model results for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4), when permafrost processes are included, terrestrial ecosystems north of 60°N could shift from being a sink to a source of CO2 by the end of the 21st century when forced by a Special Report on Emissions Scenarios (SRES) A2 climate change scenario. Between 1860 and 2100, the model response to combined CO2 fertilization and climate change changes from a sink of 68 Pg to a 27 + -7 Pg sink to 4 + -18 Pg source, depending on the processes and parameter values used. The integrated change in carbon due to climate change shifts from near zero, which is within the range of previous model estimates, to a climate-induced loss of carbon by ecosystems in the range of 25 + -3 to 85 + -16 Pg C, depending on processes included in the model, with a best estimate of a 62 + -7 Pg C loss. Methane emissions from high-latitude regions are calculated to increase from 34 Tg CH4/y to 41–70 Tg CH4/y, with increases due to CO2 fertilization, permafrost thaw, and warming-induced increased CH4 flux densities partially offset by a reduction in wetland extent. PMID:21852573
Trunk acceleration for neuroprosthetic control of standing: a pilot study.
Nataraj, Raviraj; Audu, Musa L; Kirsch, Robert F; Triolo, Ronald J
2012-02-01
This pilot study investigated the potential of using trunk acceleration feedback control of center of pressure (COP) against postural disturbances with a standing neuroprosthesis following paralysis. Artificial neural networks (ANNs) were trained to use three-dimensional trunk acceleration as input to predict changes in COP for able-bodied subjects undergoing perturbations during bipedal stance. Correlation coefficients between ANN predictions and actual COP ranged from 0.67 to 0.77. An ANN trained across all subject-normalized data was used to drive feedback control of ankle muscle excitation levels for a computer model representing a standing neuroprosthesis user. Feedback control reduced average upper-body loading during perturbation onset and recovery by 42% and peak loading by 29% compared with optimal, constant excitation.
Feedback between neutral winds and auroral arc electrodynamics
NASA Technical Reports Server (NTRS)
Lyons, L. R.; Walterscheid, R. L.
1986-01-01
The feedback between neutral atmospheric winds and the electrodynamics of a stable, discrete auroral arc is analyzed. The ionospheric current continuity equation and the equation for neutral gas acceleration by ion drag are solved simultaneously, as a function of time. The results show that, in general, the electric field in the ionosphere adjusts to neutral wind acceleration so as to keep auroral field-aligned currents and electron acceleration approximately independent of time. It is thus concluded that the neutral winds that develop as a result of the electrodynamical forcing associated with an arc do not significantly affect the intensity of the arc.
Biased feedback in brain-computer interfaces.
Barbero, Alvaro; Grosse-Wentrup, Moritz
2010-07-27
Even though feedback is considered to play an important role in learning how to operate a brain-computer interface (BCI), to date no significant influence of feedback design on BCI-performance has been reported in literature. In this work, we adapt a standard motor-imagery BCI-paradigm to study how BCI-performance is affected by biasing the belief subjects have on their level of control over the BCI system. Our findings indicate that subjects already capable of operating a BCI are impeded by inaccurate feedback, while subjects normally performing on or close to chance level may actually benefit from an incorrect belief on their performance level. Our results imply that optimal feedback design in BCIs should take into account a subject's current skill level.
Zaslansky, R; Chapman, C R; Rothaug, J; Bäckström, R; Brill, S; Davidson, E; Elessi, K; Fletcher, D; Fodor, L; Karanja, E; Konrad, C; Kopf, A; Leykin, Y; Lipman, A; Puig, M; Rawal, N; Schug, S; Ullrich, K; Volk, T; Meissner, W
2012-03-01
Post-operative pain exacts a high toll from patients, families, healthcare professionals and healthcare systems worldwide. PAIN-OUT is a research project funded by the European Union's 7th Framework Program designed to develop effective, evidence-based approaches to improve pain management after surgery, including creating a registry for feedback, benchmarking and decision support. In preparation for PAIN-OUT, we conducted a pilot study to evaluate the feasibility of international data collection with feedback to participating sites. Adult orthopaedic or general surgery patients consented to participate between May and October 2008 at 14 collaborating hospitals in 13 countries. Project staff collected patient-reported outcomes and process data from 688 patients and entered the data into an online database. Project staff in 10 institutions met the enrolment criteria of collecting data from at least 50 patients. The completeness and quality of the data, as assessed by rate of missing data, were acceptable; only 2% of process data and 0.06% of patient-reported outcome data were missing. Participating institutions received access to select items as Web-based feedback comparing their outcomes to those of the other sites, presented anonymously. We achieved proof of concept because staff and patients in all 14 sites cooperated well despite marked differences in cultures, nationalities and languages, and a central database management team was able to provide valuable feedback to all. © 2011 European Federation of International Association for the Study of Pain Chapters.
High efficiency RF amplifier development over wide dynamic range for accelerator application
NASA Astrophysics Data System (ADS)
Mishra, Jitendra Kumar; Ramarao, B. V.; Pande, Manjiri M.; Joshi, Gopal; Sharma, Archana; Singh, Pitamber
2017-10-01
Superconducting (SC) cavities in an accelerating section are designed to have the same geometrical velocity factor (βg). For these cavities, Radio Frequency (RF) power needed to accelerate charged particles varies with the particle velocity factor (β). RF power requirement from one cavity to other can vary by 2-5 dB within the accelerating section depending on the energy gain in the cavity and beam current. In this paper, we have presented an idea to improve operating efficiency of the SC RF accelerators using envelope tracking technique. A study on envelope tracking technique without feedback is carried out on a 1 kW, 325 MHz, class B (conduction angle of 180 degrees) tuned load power amplifier (PA). We have derived expressions for the efficiency and power output for tuned load amplifier operating on the envelope tracking technique. From the derived expressions, it is observed that under constant load resistance to the device (MOSFET), optimum amplifier efficiency is invariant whereas output power varies with the square of drain bias voltage. Experimental results on 1 kW PA module show that its optimum efficiency is always greater than 62% with variation less than 5% from mean value over 7 dB dynamic range. Low power amplifier modules are the basic building block for the high power amplifiers. Therefore, results for 1 kW PA modules remain valid for the high power solid state amplifiers built using these PA modules. The SC RF accelerators using these constant efficiency power amplifiers can improve overall accelerator efficiency.
Fitzharris, Michael; Liu, Sara; Stephens, Amanda N; Lenné, Michael G
2017-05-29
Real-time driver monitoring systems represent a solution to address key behavioral risks as they occur, particularly distraction and fatigue. The efficacy of these systems in real-world settings is largely unknown. This article has three objectives: (1) to document the incidence and duration of fatigue in real-world commercial truck-driving operations, (2) to determine the reduction, if any, in the incidence of fatigue episodes associated with providing feedback, and (3) to tease apart the relative contribution of in-cab warnings from 24/7 monitoring and feedback to employers. Data collected from a commercially available in-vehicle camera-based driver monitoring system installed in a commercial truck fleet operating in Australia were analyzed. The real-time driver monitoring system makes continuous assessments of driver drowsiness based on eyelid position and other factors. Data were collected in a baseline period where no feedback was provided to drivers. Real-time feedback to drivers then occurred via in-cab auditory and haptic warnings, which were further enhanced by direct feedback by company management when fatigue events were detected by external 24/7 monitors. Fatigue incidence rates and their timing of occurrence across the three time periods were compared. Relative to no feedback being provided to drivers when fatigue events were detected, in-cab warnings resulted in a 66% reduction in fatigue events, with a 95% reduction achieved by the real-time provision of direct feedback in addition to in-cab warnings (p < 0.01). With feedback, fatigue events were shorter in duration a d occurred later in the trip, and fewer drivers had more than one verified fatigue event per trip. That the provision of feedback to the company on driver fatigue events in real time provides greater benefit than feedback to the driver alone has implications for companies seeking to mitigate risks associated with fatigue. Having fewer fatigue events is likely a reflection of the device
NASA Astrophysics Data System (ADS)
Vainshtein, Igor; Baruch, Shlomi; Regev, Itai; Segal, Victor; Filis, Avishai; Riabzev, Sergey
2018-05-01
The growing demand for EO applications that work around the clock 24hr/7days a week, such as in border surveillance systems, emphasizes the need for a highly reliable cryocooler having increased operational availability and optimized system's Integrated Logistic Support (ILS). In order to meet this need, RICOR developed linear and rotary cryocoolers which achieved successfully this goal. Cryocoolers MTTF was analyzed by theoretical reliability evaluation methods, demonstrated by normal and accelerated life tests at Cryocooler level and finally verified by field data analysis derived from Cryocoolers operating at system level. The following paper reviews theoretical reliability analysis methods together with analyzing reliability test results derived from standard and accelerated life demonstration tests performed at Ricor's advanced reliability laboratory. As a summary for the work process, reliability verification data will be presented as a feedback from fielded systems.
Current Fragmentation and Particle Acceleration in Solar Flares
NASA Astrophysics Data System (ADS)
Cargill, P. J.; Vlahos, L.; Baumann, G.; Drake, J. F.; Nordlund, Å.
2012-11-01
Particle acceleration in solar flares remains an outstanding problem in plasma physics and space science. While the observed particle energies and timescales can perhaps be understood in terms of acceleration at a simple current sheet or turbulence site, the vast number of accelerated particles, and the fraction of flare energy in them, defies any simple explanation. The nature of energy storage and dissipation in the global coronal magnetic field is essential for understanding flare acceleration. Scenarios where the coronal field is stressed by complex photospheric motions lead to the formation of multiple current sheets, rather than the single monolithic current sheet proposed by some. The currents sheets in turn can fragment into multiple, smaller dissipation sites. MHD, kinetic and cellular automata models are used to demonstrate this feature. Particle acceleration in this environment thus involves interaction with many distributed accelerators. A series of examples demonstrate how acceleration works in such an environment. As required, acceleration is fast, and relativistic energies are readily attained. It is also shown that accelerated particles do indeed interact with multiple acceleration sites. Test particle models also demonstrate that a large number of particles can be accelerated, with a significant fraction of the flare energy associated with them. However, in the absence of feedback, and with limited numerical resolution, these results need to be viewed with caution. Particle in cell models can incorporate feedback and in one scenario suggest that acceleration can be limited by the energetic particles reaching the condition for firehose marginal stability. Contemporary issues such as footpoint particle acceleration are also discussed. It is also noted that the idea of a "standard flare model" is ill-conceived when the entire distribution of flare energies is considered.
Enhanced operator perception through 3D vision and haptic feedback
NASA Astrophysics Data System (ADS)
Edmondson, Richard; Light, Kenneth; Bodenhamer, Andrew; Bosscher, Paul; Wilkinson, Loren
2012-06-01
Polaris Sensor Technologies (PST) has developed a stereo vision upgrade kit for TALON® robot systems comprised of a replacement gripper camera and a replacement mast zoom camera on the robot, and a replacement display in the Operator Control Unit (OCU). Harris Corporation has developed a haptic manipulation upgrade for TALON® robot systems comprised of a replacement arm and gripper and an OCU that provides haptic (force) feedback. PST and Harris have recently collaborated to integrate the 3D vision system with the haptic manipulation system. In multiple studies done at Fort Leonard Wood, Missouri it has been shown that 3D vision and haptics provide more intuitive perception of complicated scenery and improved robot arm control, allowing for improved mission performance and the potential for reduced time on target. This paper discusses the potential benefits of these enhancements to robotic systems used for the domestic homeland security mission.
Strandbygaard, Jeanett; Bjerrum, Flemming; Maagaard, Mathilde; Winkel, Per; Larsen, Christian Rifbjerg; Ringsted, Charlotte; Gluud, Christian; Grantcharov, Teodor; Ottesen, Bent; Sorensen, Jette Led
2013-05-01
To investigate the impact of instructor feedback versus no instructor feedback when training a complex operational task on a laparoscopic virtual reality simulator. : Simulators are now widely accepted as a training tool, but there is insufficient knowledge about how much feedback is necessary, which is useful for sustainable implementation. A randomized trial complying with CONSORT Statement. All participants had to reach a predefined proficiency level for a complex operational task on a virtual reality simulator. The intervention group received standardized instructor feedback a maximum of 3 times. The control group did not receive instructor feedback. Participants were senior medical students without prior laparoscopic experience (n = 99). Outcome measures were time, repetitions, and performance score to reach a predefined proficiency level. Furthermore, influence of sex and perception of own surgical skills were examined. Time (in minutes) and repetitions were reduced in the intervention group (162 vs 342 minutes; P < 0.005) and (29 vs 65 repetitions; P < 0.005). The control group achieved a higher performance score than the intervention group (57% vs 49%; P = 0.004). Men used less time (in minutes) than women (P = 0.037), but no sex difference was observed for repetitions (P = 0.20). Participants in the intervention group had higher self-perception regarding surgical skills after the trial (P = 0.011). Instructor feedback increases the efficiency when training a complex operational task on a virtual reality simulator; time and repetitions used to achieve a predefined proficiency level were significantly reduced in the group that received instructor feedback compared with the control group. NCT01497782.
Trunk Acceleration for Neuroprosthetic Control of Standing – a Pilot Study
Audu, Musa L.; Kirsch, Robert F.; Triolo, Ronald J.
2013-01-01
This pilot study investigated the potential of using trunk acceleration feedback control of center of pressure (COP) against postural disturbances with a standing neuroprosthesis following paralysis. Artificial neural networks (ANNs) were trained to use three-dimensional trunk acceleration as input to predict changes in COP for able-bodied subjects undergoing perturbations during bipedal stance. Correlation coefficients between ANN predictions and actual COP ranged from 0.67 to 0.77. An ANN trained across all subject-normalized data was used to drive feedback control of ankle muscle excitation levels for a computer model representing a standing neuroprosthesis user. Feedback control reduced average upper-body loading during perturbation onset and recovery by 42% and peak loading by 29% compared to optimal, constant excitation. PMID:21975251
Neuro-fuzzy control of structures using acceleration feedback
NASA Astrophysics Data System (ADS)
Schurter, Kyle C.; Roschke, Paul N.
2001-08-01
This paper described a new approach for the reduction of environmentally induced vibration in constructed facilities by way of a neuro-fuzzy technique. The new control technique is presented and tested in a numerical study that involves two types of building models. The energy of each building is dissipated through magnetorheological (MR) dampers whose damping properties are continuously updated by a fuzzy controller. This semi-active control scheme relies on the development of a correlation between the accelerations of the building (controller input) and the voltage applied to the MR damper (controller output). This correlation forms the basis for the development of an intelligent neuro-fuzzy control strategy. To establish a context for assessing the effectiveness of the semi-active control scheme, responses to earthquake excitation are compared with passive strategies that have similar authority for control. According to numerical simulation, MR dampers are less effective control mechanisms than passive dampers with respect to a single degree of freedom (DOF) building model. On the other hand, MR dampers are predicted to be superior when used with multiple DOF structures for reduction of lateral acceleration.
SIN accelerator, operational experience and improvement programs
DOE Office of Scientific and Technical Information (OSTI.GOV)
Joho, W.; Olivo, M.; Stammbach, T.
1977-06-01
The SIN meson facility, in operation since 1974, consists of a 590 MeV ring cyclotron for protons and a 72 MeV injector cyclotron. The average beam current on target is presently about 50 ..mu..A, the peak being 112 ..mu..A. Extraction efficiency, once considered a severe handicap for cyclotrons, is now 99.6 to 99.9% for the ring cyclotron and about 90% for the injector. Many improvements in both accelerators allow single turn extraction in the ring cyclotron. The present current limit is given by the injector, while the ring itself could accept now a 600 ..mu..A beam, with 2 to 4more » mA as an ultimate limit. Some muon experiments require a pulsed beam with on-off times in the order of the lifetime of the muon. First trials with beam pulse frequencies of 200 and 400 kHz and a 50% duty cycle have been successful.« less
Rf Feedback free electron laser
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.
NASA Astrophysics Data System (ADS)
Hodges, M.; Barzilov, A.; Chen, Y.; Lowe, D.
2016-10-01
The bremsstrahlung photon flux from the UNLV particle accelerator (Varian M6 model) was determined using MCNP5 code for 3 MeV and 6 MeV incident electrons. Human biological equivalent dose rates due to accelerator operation were evaluated using the photon flux with the flux-to-dose conversion factors. Dose rates were computed for the accelerator facility for M6 linac use under different operating conditions. The results showed that the use of collimators and linac internal shielding significantly reduced the dose rates throughout the facility. It was shown that the walls of the facility, in addition to the earthen berm enveloping the building, provide equivalent shielding to reduce dose rates outside to below the 2 mrem/h limit.
Roh, Taehwan; Song, Kiseok; Cho, Hyunwoo; Shin, Dongjoo; Yoo, Hoi-Jun
2014-12-01
A wearable neuro-feedback system is proposed with a low-power neuro-feedback SoC (NFS), which supports mental status monitoring with encephalography (EEG) and transcranial electrical stimulation (tES) for neuro-modulation. Self-configured independent component analysis (ICA) is implemented to accelerate source separation at low power. Moreover, an embedded support vector machine (SVM) enables online source classification, configuring the ICA accelerator adaptively depending on the types of the decomposed components. Owing to the hardwired accelerating functions, the NFS dissipates only 4.45 mW to yield 16 independent components. For non-invasive neuro-modulation, tES stimulation up to 2 mA is implemented on the SoC. The NFS is fabricated in 130-nm CMOS technology.
Rotation in a reversed field pinch with active feedback stabilization of resistive wall modes
NASA Astrophysics Data System (ADS)
Cecconello, M.; Menmuir, S.; Brunsell, P. R.; Kuldkepp, M.
2006-09-01
Active feedback stabilization of multiple resistive wall modes (RWMs) has been successfully proven in the EXTRAP T2R reversed field pinch. One of the features of plasma discharges operated with active feedback stabilization, in addition to the prolongation of the plasma discharge, is the sustainment of the plasma rotation. Sustained rotation is observed both for the internally resonant tearing modes (TMs) and the intrinsic impurity oxygen ions. Good quantitative agreement between the toroidal rotation velocities of both is found: the toroidal rotation is characterized by an acceleration phase followed, after one wall time, by a deceleration phase that is slower than in standard discharges. The TMs and the impurity ions rotate in the same poloidal direction with also similar velocities. Poloidal and toroidal velocities have comparable amplitudes and a simple model of their radial profile reproduces the main features of the helical angular phase velocity. RWMs feedback does not qualitatively change the TMs behaviour and typical phenomena such as the dynamo and the 'slinky' are still observed. The improved sustainment of the plasma and TMs rotation occurs also when feedback only acts on internally non-resonant RWMs. This may be due to an indirect positive effect, through non-linear coupling between TMs and RWMs, of feedback on the TMs or to a reduced plasma-wall interaction affecting the plasma flow rotation. Electromagnetic torque calculations show that with active feedback stabilization the TMs amplitude remains well below the locking threshold condition for a thick shell. Finally, it is suggested that active feedback stabilization of RWMs and current profile control techniques can be employed simultaneously thus improving both the plasma duration and its confinement properties.
Improving Retrieval Performance by Relevance Feedback.
ERIC Educational Resources Information Center
Salton, Gerard; Buckley, Chris
1990-01-01
Briefly describes the principal relevance feedback methods that have been introduced over the years and evaluates the effectiveness of the methods in producing improved query formulations. Prescriptions are given for conducting text retrieval operations iteratively using relevance feedback. (24 references) (Author/CLB)
Reducing Operating Room Costs Through Real-Time Cost Information Feedback: A Pilot Study.
Tabib, Christian H; Bahler, Clinton D; Hardacker, Thomas J; Ball, Kevin M; Sundaram, Chandru P
2015-08-01
To create a protocol for providing real-time operating room (OR) cost feedback to surgeons. We hypothesize that this protocol will reduce costs in a responsible way without sacrificing quality of care. All OR costs were obtained and recorded for robot-assisted partial nephrectomy and laparoscopic donor nephrectomy. Before the beginning of this project, costs pertaining to the 20 most recent cases were analyzed. Items were identified from previous cases as modifiable for replacement or omission. Timely feedback of total OR costs and cost of each item used was provided to the surgeon after each case, and costs were analyzed. A cost analysis of the robot-assisted partial nephrectomy before the washout period indicates expenditures of $5243.04 per case. Ten recommended modifiable items were found to have an average per case cost of $1229.33 representing 23.4% of the total cost. A postwashout period cost analysis found the total OR cost decreased by $899.67 (17.2%) because of changes directly related to the modifiable items. Therefore, 73.2% of the possible identified savings was realized. The same stepwise approach was applied to laparoscopic donor nephrectomies. The average total cost per case before the washout period was $3530.05 with $457.54 attributed to modifiable items. After the washout period, modifiable items costs were reduced by $289.73 (8.0%). No complications occurred in the donor nephrectomy cases while one postoperative complication occurred in the partial nephrectomy group. Providing surgeons with feedback related to OR costs may lead to a change in surgeon behavior and decreased overall costs. Further studies are needed to show equivalence in patient outcomes.
Lobzin, V S; Tsatskina, N D
1989-01-01
A total of 192 patients with Bell paralysis were studied. In 32 a technique of biofeedback training was applied to accelerate the restoration of mimetic muscles with EMG feedback. Clinical and electrophysiological data confirmed the efficiency of this technique in terms of considerably accelerated rehabilitation.
NASA Technical Reports Server (NTRS)
Correia, Manning J.; Luke, Brian L.; McGrath, Braden J.; Clark, John B.; Rupert, Angus H.
1996-01-01
While considerable attention has been given to visual-vestibular interaction (VVI) during angular motion of the head as might occur during an aircraft spin, much less attention has been given to VVI during linear motion of the head. Such interaction might occur, for example, while viewing a stationary or moving display during vertical take-off and landing operations Research into linear VVI, particularly during prolonged periods of linear acceleration, has been hampered by the unavailability of a programmable translator capable of large excursions We collaborated with Otis Elevator Co. and used their research tower and elevator, whose motion could be digitally programmed, to vertically translate human subjects over a distance of 92.3 meters with a peak linear acceleration of 2 meters/sec(exp 2) During pulsatile or sinusoidal translation, the subjects viewed moving stripes (optokinetic stimulus) or a fixed point source (light emitting diode, led, display), respectively and it was generally found that. The direction of linear acceleration relative to the cardinal head axes and the direction of the slow component of optokinetic nystagmus (OKN) determined the extent of VVI during concomitant stripe motion and linear acceleration. Acceleration along the z head axis (A(sub z)) produced the largest VVI, particularly when the slow component of OKN was in the same direction as eye movements produced by the linear acceleration and Eye movements produced by linear acceleration are suppressed by viewing a fixed target at frequencies below 10 Hz But, above this frequency the suppression produced by VVI is removed. Finally, as demonstrated in non-human primates, vergence of the eyes appears to modulate the vertical eye movement response to linear acceleration in humans.
Rf feedback free electron laser
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.
Perioperative feedback in surgical training: A systematic review.
McKendy, Katherine M; Watanabe, Yusuke; Lee, Lawrence; Bilgic, Elif; Enani, Ghada; Feldman, Liane S; Fried, Gerald M; Vassiliou, Melina C
2017-07-01
Changes in surgical training have raised concerns about residents' operative exposure and preparedness for independent practice. One way of addressing this concern is by optimizing teaching and feedback in the operating room (OR). The objective of this study was to perform a systematic review on perioperative teaching and feedback. A systematic literature search identified articles from 1994 to 2014 that addressed teaching, feedback, guidance, or debriefing in the perioperative period. Data was extracted according to ENTREQ guidelines, and a qualitative analysis was performed. Thematic analysis of the 26 included studies identified four major topics. Observation of teaching behaviors in the OR described current teaching practices. Identification of effective teaching strategies analyzed teaching behaviors, differentiating positive and negative teaching strategies. Perceptions of teaching behaviors described resident and attending satisfaction with teaching in the OR. Finally models for delivering structured feedback cited examples of feedback strategies and measured their effectiveness. This study provides an overview of perioperative teaching and feedback for surgical trainees and identifies a need for improved quality and quantity of structured feedback. Copyright © 2016 Elsevier Inc. All rights reserved.
NASA Technical Reports Server (NTRS)
Duerksen, Gary L.; Krainak, Michael A.
1998-01-01
Single-frequency operation of uncoated Fabry-Perot laser diodes is demonstrated by phase- locking the laser oscillations through self-injection seeding with feedback from a fiber Bragg grating. By precisely tuning the laser temperature so that an axial-mode coincides with the short-wavelength band edge of the grating, the phase of the feedback is made conjugate to that of the axial mode, locking the phase of the laser oscillations to that mode.
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…
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.
Motivation in vigilance - Effects of self-evaluation and experimenter-controlled feedback.
NASA Technical Reports Server (NTRS)
Warm, J. S.; Kanfer, F. H.; Kuwada, S.; Clark, J. L.
1972-01-01
Vigilance experiments have been performed to study the relative efficiency of feedback operations in enhancing vigilance performance. Two feedback operations were compared - i.e., experimenter-controlled feedback in the form of knowledge of results (KR) regarding response times to signal detections, and subject-controlled feedback in the form of self-evaluation (SE) of response times to signal detections. The subjects responded to the aperiodic offset of a visual signal during a 1-hr vigil. Both feedback operations were found to enhance performance efficiency: subjects in the KR and SE conditions had faster response times than controls receiving no evaluative feedback. Moreover, the data of the KR and SE groups did not differ significantly from each other. The results are discussed in terms of the hypothesis that self-evaluation is a critical factor underlying the incentive value of KR in vigilance tasks.
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…
Leang, Sarom S; Rendell, Alistair P; Gordon, Mark S
2014-03-11
Increasingly, modern computer systems comprise a multicore general-purpose processor augmented with a number of special purpose devices or accelerators connected via an external interface such as a PCI bus. The NVIDIA Kepler Graphical Processing Unit (GPU) and the Intel Phi are two examples of such accelerators. Accelerators offer peak performances that can be well above those of the host processor. How to exploit this heterogeneous environment for legacy application codes is not, however, straightforward. This paper considers how matrix operations in typical quantum chemical calculations can be migrated to the GPU and Phi systems. Double precision general matrix multiply operations are endemic in electronic structure calculations, especially methods that include electron correlation, such as density functional theory, second order perturbation theory, and coupled cluster theory. The use of approaches that automatically determine whether to use the host or an accelerator, based on problem size, is explored, with computations that are occurring on the accelerator and/or the host. For data-transfers over PCI-e, the GPU provides the best overall performance for data sizes up to 4096 MB with consistent upload and download rates between 5-5.6 GB/s and 5.4-6.3 GB/s, respectively. The GPU outperforms the Phi for both square and nonsquare matrix multiplications.
A coherent optical feedback system for optical information processing
NASA Technical Reports Server (NTRS)
Jablonowski, D. P.; Lee, S. H.
1975-01-01
A unique optical feedback system for coherent optical data processing is described. With the introduction of feedback, the well-known transfer function for feedback systems is obtained in two dimensions. Operational details of the optical feedback system are given. Experimental results of system applications in image restoration, contrast control and analog computation are presented.
Ion accelerator systems for high power 30 cm thruster operation
NASA Technical Reports Server (NTRS)
Aston, G.
1982-01-01
Two and three-grid accelerator systems for high power ion thruster operation were investigated. Two-grid translation tests show that over compensation of the 30 cm thruster SHAG grid set spacing the 30 cm thruster radial plasma density variation and by incorporating grid compensation only sufficient to maintain grid hole axial alignment, it is shown that beam current gains as large as 50% can be realized. Three-grid translation tests performed with a simulated 30 cm thruster discharge chamber show that substantial beamlet steering can be reliably affected by decelerator grid translation only, at net-to-total voltage ratios as low as 0.05.
Luce, John S.
1978-01-01
A collective field accelerator which operates with a vacuum diode and utilizes a grooved cathode and a dielectric anode that operates with a relativistic electron beam with a .nu./.gamma. of .about. 1, and a plurality of dielectric lenses having an axial magnetic field thereabout to focus the collectively accelerated electrons and ions which are ejected from the anode. The anode and lenses operate as unoptimized r-f cavities which modulate and focus the beam.
Strength of German accent under altered auditory feedback
HOWELL, PETER; DWORZYNSKI, KATHARINA
2007-01-01
Borden’s (1979, 1980) hypothesis that speakers with vulnerable speech systems rely more heavily on feedback monitoring than do speakers with less vulnerable systems was investigated. The second language (L2) of a speaker is vulnerable, in comparison with the native language, so alteration to feedback should have a detrimental effect on it, according to this hypothesis. Here, we specifically examined whether altered auditory feedback has an effect on accent strength when speakers speak L2. There were three stages in the experiment. First, 6 German speakers who were fluent in English (their L2) were recorded under six conditions—normal listening, amplified voice level, voice shifted in frequency, delayed auditory feedback, and slowed and accelerated speech rate conditions. Second, judges were trained to rate accent strength. Training was assessed by whether it was successful in separating German speakers speaking English from native English speakers, also speaking English. In the final stage, the judges ranked recordings of each speaker from the first stage as to increasing strength of German accent. The results show that accents were more pronounced under frequency-shifted and delayed auditory feedback conditions than under normal or amplified feedback conditions. Control tests were done to ensure that listeners were judging accent, rather than fluency changes caused by altered auditory feedback. The findings are discussed in terms of Borden’s hypothesis and other accounts about why altered auditory feedback disrupts speech control. PMID:11414137
Climate change and the permafrost carbon feedback
Schuur, E.A.G.; McGuire, A. David; Schädel, C.; Grosse, G.; Harden, J.W.; Hayes, D.J.; Hugelius, G.; Koven, C.D.; Kuhry, P.; Lawrence, D.M.; Natali, Susan M.; Olefeldt, David; Romanovsky, V.E.; Schaefer, K.; Turetsky, M.R.; Treat, C.C.; Vonk, J.E.
2015-01-01
Large quantities of organic carbon are stored in frozen soils (permafrost) within Arctic and sub-Arctic regions. A warming climate can induce environmental changes that accelerate the microbial breakdown of organic carbon and the release of the greenhouse gases carbon dioxide and methane. This feedback can accelerate climate change, but the magnitude and timing of greenhouse gas emission from these regions and their impact on climate change remain uncertain. Here we find that current evidence suggests a gradual and prolonged release of greenhouse gas emissions in a warming climate and present a research strategy with which to target poorly understood aspects of permafrost carbon dynamics.
Climate change and the permafrost carbon feedback.
Schuur, E A G; McGuire, A D; Schädel, C; Grosse, G; Harden, J W; Hayes, D J; Hugelius, G; Koven, C D; Kuhry, P; Lawrence, D M; Natali, S M; Olefeldt, D; Romanovsky, V E; Schaefer, K; Turetsky, M R; Treat, C C; Vonk, J E
2015-04-09
Large quantities of organic carbon are stored in frozen soils (permafrost) within Arctic and sub-Arctic regions. A warming climate can induce environmental changes that accelerate the microbial breakdown of organic carbon and the release of the greenhouse gases carbon dioxide and methane. This feedback can accelerate climate change, but the magnitude and timing of greenhouse gas emission from these regions and their impact on climate change remain uncertain. Here we find that current evidence suggests a gradual and prolonged release of greenhouse gas emissions in a warming climate and present a research strategy with which to target poorly understood aspects of permafrost carbon dynamics.
A New Concept of Controller for Accelerators' Magnet Power Supplies
NASA Astrophysics Data System (ADS)
Visintini, Roberto; Cleva, Stefano; Cautero, Marco; Ciesla, Tomasz
2016-04-01
The complexity of a particle accelerator implies the remote control of very large numbers of devices, with many different typologies, either distributed along the accelerator or concentrated in locations, often far away from each other. Local and global control systems handle the devices through dedicated communication channels and interfaces. Each controlled device is practically a “smart node” performing a specific task. In addition, very often, those tasks are managed in real-time mode. The performances required to the control interface has an influence on the cost of the distributed nodes as well as on their hardware and software implementation. In large facilities (e.g. CERN) the “smart nodes” derive from specific in-house developments. Alternatively, it is possible to find on the market commercial devices, whose performances (and prices) are spread over a broad range, and spanning from proprietary design (customizable to the user's needs) to open source/design. In this paper, we will describe some applications of smart nodes in the particle accelerators field, with special focus on the power supplies for magnets. In modern accelerators, in fact, magnets and their associated power supplies constitute systems distributed along the accelerator itself, and strongly interfaced with the remote control system as well as with more specific (and often more demanding) orbit/trajectory feedback systems. We will give examples of actual systems, installed and operational on two light sources, Elettra and FERMI, located in the Elettra Research Center in Trieste, Italy.
NASA Astrophysics Data System (ADS)
Kim, S.-H.; Afanador, R.; Barnhart, D. L.; Crofford, M.; Degraff, B. D.; Doleans, M.; Galambos, J.; Gold, S. W.; Howell, M. P.; Mammosser, J.; McMahan, C. J.; Neustadt, T. S.; Peters, C.; Saunders, J. W.; Strong, W. H.; Vandygriff, D. J.; Vandygriff, D. M.
2017-04-01
The Spallation Neutron Source (SNS) has acquired extensive operational experience of a pulsed proton superconducting linear accelerator (SCL) as a user facility. Numerous lessons have been learned in its first 10 years operation to achieve a stable and reliable operation of the SCL. In this paper, an overview of the SNS SCL design, qualification of superconducting radio frequency (SRF) cavities and ancillary subsystems, an overview of the SNS cryogenic system, the SCL operation including SCL output energy history and downtime statistics, performance stability of the SRF cavities, efforts for SRF cavity performance recovery and improvement at the SNS, and maintenance activities for cryomodules are introduced.
Kim, Sang-Ho; Afanador, Ralph; Barnhart, Debra L.; ...
2017-02-04
The Spallation Neutron Source (SNS) has acquired extensive operational experience of a pulsed proton superconducting linear accelerator (SCL) as a user facility. Numerous lessons have been learned in its first 10 years operation to achieve a stable and reliable operation of the SCL. In this paper, an overview of the SNS SCL design, qualification of superconducting radio frequency (SRF) cavities and ancillary subsystems, an overview of the SNS cryogenic system, the SCL operation including SCL output energy history and downtime statistics, performance stability of the SRF cavities, efforts for SRF cavity performance recovery and improvement at the SNS, and maintenancemore » activities for cryomodules are introduced.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kim, Sang-Ho; Afanador, Ralph; Barnhart, Debra L.
The Spallation Neutron Source (SNS) has acquired extensive operational experience of a pulsed proton superconducting linear accelerator (SCL) as a user facility. Numerous lessons have been learned in its first 10 years operation to achieve a stable and reliable operation of the SCL. In this paper, an overview of the SNS SCL design, qualification of superconducting radio frequency (SRF) cavities and ancillary subsystems, an overview of the SNS cryogenic system, the SCL operation including SCL output energy history and downtime statistics, performance stability of the SRF cavities, efforts for SRF cavity performance recovery and improvement at the SNS, and maintenancemore » activities for cryomodules are introduced.« less
Hill, Holger
2015-01-01
In a case study, Schaffert and Mattes reported the application of acoustic feedback (sonification) to optimise the time course of boat acceleration. The authors attributed an increased boat speed in the feedback condition to an optimised boat acceleration (mainly during the recovery phase). However, in rowing it is biomechanically impossible to increase the boat speed significantly by reducing the fluctuations in boat acceleration during the rowing cycle. To assess such a, potentially small, optimising effect experimentally, the confounding variables must be controlled very accurately (that is especially the propulsive forces must be kept constant between experimental conditions or the differences in propulsive forces between conditions must be much smaller than the effects on boat speed resulting from an optimised movement pattern). However, this was not controlled adequately by the authors. Instead, the presented boat acceleration data show that the increased boat speed under acoustic feedback was due to increased propulsive forces.
Safety implications of providing real-time feedback to distracted drivers.
Donmez, Birsen; Boyle, Linda Ng; Lee, John D
2007-05-01
A driving simulator study was conducted to assess whether real-time feedback on a driver's state can influence the driver's interaction with in-vehicle information systems (IVIS). Previous studies have shown that IVIS tasks can undermine driver safety by increasing driver distraction. Thus, mitigating driver distraction using a feedback mechanism appears promising. This study was designed to test real-time feedback that alerts drivers based on their off-road eye glances. Feedback was displayed in two display locations (vehicle-centered, and IVIS-centered) to 16 young and 13 middle-aged drivers. Distraction was observed as problematic for both age groups with delayed responses to a lead vehicle-braking event as indicated by delayed accelerator releases. Significant benefits were not observed for braking and steering behavior for this experiment, but there was a significant change in drivers' interaction with IVIS. When given feedback on their distracted state, drivers looked at the in-vehicle display less frequently regardless of where feedback was displayed in the vehicle. This indicates that real-time feedback based on the driver state can positively alter driver's engagement in distracting activities, helping them attend better to the roadway.
Coherent control of plasma dynamics by feedback-optimized wavefront manipulation
DOE Office of Scientific and Technical Information (OSTI.GOV)
He, Z.-H.; Hou, B.; Gao, G.
2015-05-15
Plasmas generated by an intense laser pulse can support coherent structures such as large amplitude wakefield that can affect the outcome of an experiment. We investigate the coherent control of plasma dynamics by feedback-optimized wavefront manipulation using a deformable mirror. The experimental outcome is directly used as feedback in an evolutionary algorithm for optimization of the phase front of the driving laser pulse. In this paper, we applied this method to two different experiments: (i) acceleration of electrons in laser driven plasma waves and (ii) self-compression of optical pulses induced by ionization nonlinearity. The manipulation of the laser wavefront leadsmore » to orders of magnitude improvement to electron beam properties such as the peak charge, beam divergence, and transverse emittance. The demonstration of coherent control for plasmas opens new possibilities for future laser-based accelerators and their applications.« less
Predicting induced radioactivity for the accelerator operations at the Taiwan Photon Source.
Sheu, R J; Jiang, S H
2010-12-01
This study investigates the characteristics of induced radioactivity due to the operations of a 3-GeV electron accelerator at the Taiwan Photon Source (TPS). According to the beam loss analysis, the authors set two representative irradiation conditions for the activation analysis. The FLUKA Monte Carlo code has been used to predict the isotope inventories, residual activities, and remanent dose rates as a function of time. The calculation model itself is simple but conservative for the evaluation of induced radioactivity in a light source facility. This study highlights the importance of beam loss scenarios and demonstrates the great advantage of using FLUKA in comparing the predicted radioactivity with corresponding regulatory limits. The calculated results lead to the conclusion that, due to fairly low electron consumption, the radioactivity induced in the accelerator components and surrounding concrete walls of the TPS is rather moderate and manageable, while the possible activation of air and cooling water in the tunnel and their environmental releases are negligible.
Ludlow, Aaron D; Benítez-Llambay, Alejandro; Schaller, Matthieu; Theuns, Tom; Frenk, Carlos S; Bower, Richard; Schaye, Joop; Crain, Robert A; Navarro, Julio F; Fattahi, Azadeh; Oman, Kyle A
2017-04-21
We analyze the total and baryonic acceleration profiles of a set of well-resolved galaxies identified in the eagle suite of hydrodynamic simulations. Our runs start from the same initial conditions but adopt different prescriptions for unresolved stellar and active galactic nuclei feedback, resulting in diverse populations of galaxies by the present day. Some of them reproduce observed galaxy scaling relations, while others do not. However, regardless of the feedback implementation, all of our galaxies follow closely a simple relationship between the total and baryonic acceleration profiles, consistent with recent observations of rotationally supported galaxies. The relation has small scatter: Different feedback implementations-which produce different galaxy populations-mainly shift galaxies along the relation rather than perpendicular to it. Furthermore, galaxies exhibit a characteristic acceleration g_{†}, above which baryons dominate the mass budget, as observed. These observations, consistent with simple modified Newtonian dynamics, can be accommodated within the standard cold dark matter paradigm.
Haptic seat for fuel economy feedback
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.
Terahertz-driven linear electron acceleration
Nanni, Emilio A.; Huang, Wenqian R.; Hong, Kyung-Han; Ravi, Koustuban; Fallahi, Arya; Moriena, Gustavo; Dwayne Miller, R. J.; Kärtner, Franz X.
2015-01-01
The cost, size and availability of electron accelerators are dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency accelerating structures operate with 30–50 MeV m−1 gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional radio-frequency structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing requirements due to the short wavelength of operation. Here we demonstrate linear acceleration of electrons with keV energy gain using optically generated terahertz pulses. Terahertz-driven accelerating structures enable high-gradient electron/proton accelerators with simple accelerating structures, high repetition rates and significant charge per bunch. These ultra-compact terahertz accelerators with extremely short electron bunches hold great potential to have a transformative impact for free electron lasers, linear colliders, ultrafast electron diffraction, X-ray science and medical therapy with X-rays and electron beams. PMID:26439410
Terahertz-driven linear electron acceleration
Nanni, Emilio A.; Huang, Wenqian R.; Hong, Kyung-Han; ...
2015-10-06
The cost, size and availability of electron accelerators are dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency accelerating structures operate with 30–50 MeVm -1 gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional radio-frequency structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing requirements due to the short wavelength of operation. Here we demonstrate linear acceleration of electrons with keV energy gain using optically generated terahertz pulses. Terahertz-driven accelerating structures enable high-gradient electron/protonmore » accelerators with simple accelerating structures, high repetition rates and significant charge per bunch. As a result, these ultra-compact terahertz accelerators with extremely short electron bunches hold great potential to have a transformative impact for free electron lasers, linear colliders, ultrafast electron diffraction, X-ray science and medical therapy with X-rays and electron beams.« less
Blauch, A J; Schiano, J L; Ginsberg, M D
2000-06-01
The performance of a nuclear resonance detection system can be quantified using binary detection theory. Within this framework, signal averaging increases the probability of a correct detection and decreases the probability of a false alarm by reducing the variance of the noise in the average signal. In conjunction with signal averaging, we propose another method based on feedback control concepts that further improves detection performance. By maximizing the nuclear resonance signal amplitude, feedback raises the probability of correct detection. Furthermore, information generated by the feedback algorithm can be used to reduce the probability of false alarm. We discuss the advantages afforded by feedback that cannot be obtained using signal averaging. As an example, we show how this method is applicable to the detection of explosives using nuclear quadrupole resonance. Copyright 2000 Academic Press.
Coherent feedback control of a single qubit in diamond
NASA Astrophysics Data System (ADS)
Hirose, Masashi; Cappellaro, Paola
2016-04-01
Engineering desired operations on qubits subjected to the deleterious effects of their environment is a critical task in quantum information processing, quantum simulation and sensing. The most common approach relies on open-loop quantum control techniques, including optimal-control algorithms based on analytical or numerical solutions, Lyapunov design and Hamiltonian engineering. An alternative strategy, inspired by the success of classical control, is feedback control. Because of the complications introduced by quantum measurement, closed-loop control is less pervasive in the quantum setting and, with exceptions, its experimental implementations have been mainly limited to quantum optics experiments. Here we implement a feedback-control algorithm using a solid-state spin qubit system associated with the nitrogen vacancy centre in diamond, using coherent feedback to overcome the limitations of measurement-based feedback, and show that it can protect the qubit against intrinsic dephasing noise for milliseconds. In coherent feedback, the quantum system is connected to an auxiliary quantum controller (ancilla) that acquires information about the output state of the system (by an entangling operation) and performs an appropriate feedback action (by a conditional gate). In contrast to open-loop dynamical decoupling techniques, feedback control can protect the qubit even against Markovian noise and for an arbitrary period of time (limited only by the coherence time of the ancilla), while allowing gate operations. It is thus more closely related to quantum error-correction schemes, although these require larger and increasing qubit overheads. Increasing the number of fresh ancillas enables protection beyond their coherence time. We further evaluate the robustness of the feedback protocol, which could be applied to quantum computation and sensing, by exploring a trade-off between information gain and decoherence protection, as measurement of the ancilla-qubit correlation
FERMILAB ACCELERATOR R&D PROGRAM TOWARDS INTENSITY FRONTIER ACCELERATORS : STATUS AND PROGRESS
DOE Office of Scientific and Technical Information (OSTI.GOV)
Shiltsev, Vladimir
2016-11-15
The 2014 P5 report indicated the accelerator-based neutrino and rare decay physics research as a centrepiece of the US domestic HEP program at Fermilab. Operation, upgrade and development of the accelerators for the near- term and longer-term particle physics program at the Intensity Frontier face formidable challenges. Here we discuss key elements of the accelerator physics and technology R&D program toward future multi-MW proton accelerators and present its status and progress. INTENSITY FRONTIER ACCELERATORS
Implementing Audio Digital Feedback Loop Using the National Instruments RIO System
DOE Office of Scientific and Technical Information (OSTI.GOV)
Huang, G.; Byrd, J. M.
2006-11-20
Development of system for high precision RF distribution and laser synchronization at Berkeley Lab has been ongoing for several years. Successful operation of these systems requires multiple audio bandwidth feedback loops running at relatively high gains. Stable operation of the feedback loops requires careful design of the feedback transfer function. To allow for flexible and compact implementation, we have developed digital feedback loops on the National Instruments Reconfigurable Input/Output (RIO) platform. This platform uses an FPGA and multiple I/Os that can provide eight parallel channels running different filters. We present the design and preliminary experimental results of this system.
Fukuda, Hiroyuki; Chen, Cindy; Mantyh, Christopher; Ludwig, Kirk; Pappas, Theodore N; Takahashi, Toku
2006-04-01
Post-operative ileus (POI) is a transient bowel dysmotility after operation. We have previously shown that laparotomy alone significantly delayed gastrointestinal (GI) transit, compared to anesthesia alone. The GI transit was further delayed after laparotomy plus intestinal manipulation. Dai-Kenchu-to (DKT), an herbal medicine, has been used for treating adhesive bowel obstruction in Japan. We studied whether DKT improves delayed GI transit after the operation, with or without morphine administration in rats. Under isoflurane anesthesia, POI was induced by laparotomy with intestinal manipulation. Immediately after the operation, the rats received 51Cr by gavage. Three hours after the operation, the rats were sacrificed and GI transit was estimated by calculating the geometric center (GC). DKT (120, 360, and 1,200 mg/kg) were administered by gavage after the operation, with or without morphine administration (1 mg/kg s.c.). A muscarinic receptor antagonist (atropine; 50 mug/kg), a 5HT3 receptor antagonist (ondansetron; 1 mg/kg) and a 5HT4 receptor antagonist (GR113,808; 3 mg/kg) were administered before the operation. Truncal vagotomy was performed preceding the operation. Laparotomy with intestinal manipulation produced a significant delay in GI transit (GC = 2.93 +/- 0.16), compared to that of anesthesia alone (9.51 +/- 0.45). DKT at the dose of 360 mg/kg (GC = 3.77 +/- 0.10, P < 0.01) and 1,200 mg/kg (GC = 3.77 +/- 0.20, P < 0.01) significantly accelerated delayed GI transit induced by operation. Ondansetron, GR113,808, atropine, and truncal vagotomy abolished the stimulatory effect of DKT (360 mg/kg). When morphine was administered, GI transit was further reduced (GC = 1.97 +/- 0.10). DKT at the dose of 360 mg/kg (GC = 2.81 +/- 0.22, P < 0.05) and 1,200 mg/kg (GC = 2.87 +/- 0.23, P < 0.05) significantly improved delayed GI transit in morphine treated rats. DKT accelerates delayed GI transit induced by intestinal manipulation with and without concomitant morphine
Coastal marsh response to historical and future sea-level acceleration
Kirwan, M.; Temmerman, S.
2009-01-01
We consider the response of marshland to accelerations in the rate of sea-level rise by utilizing two previously described numerical models of marsh elevation. In a model designed for the Scheldt Estuary (Belgium-SW Netherlands), a feedback between inundation depth and suspended sediment concentrations allows marshes to quickly adjust their elevation to a change in sea-level rise rate. In a model designed for the North Inlet Estuary (South Carolina), a feedback between inundation and vegetation growth allows similar adjustment. Although the models differ in their approach, we find that they predict surprisingly similar responses to sea-level change. Marsh elevations adjust to a step change in the rate of sea-level rise in about 100 years. In the case of a continuous acceleration in the rate of sea-level rise, modeled accretion rates lag behind sea-level rise rates by about 20 years, and never obtain equilibrium. Regardless of the style of acceleration, the models predict approximately 6-14 cm of marsh submergence in response to historical sea-level acceleration, and 3-4 cm of marsh submergence in response to a projected scenario of sea-level rise over the next century. While marshes already low in the tidal frame would be susceptible to these depth changes, our modeling results suggest that factors other than historical sea-level acceleration are more important for observations of degradation in most marshes today.
Electrothermal feedback in kinetic inductance detectors
NASA Astrophysics Data System (ADS)
Guruswamy, T.; Thomas, C. N.; Withington, S.; Goldie, D. J.
2017-06-01
In kinetic inductance detectors (KIDs) and other similar applications of superconducting microresonators, both the large and small-signal behaviour of the device may be affected by electrothermal feedback. Microwave power applied to read out the device is absorbed by and heats the superconductor quasiparticles, changing the superconductor conductivity and hence the readout power absorbed in a positive or negative feedback loop. In this work, we explore numerically the implications of an extensible theoretical model of a generic superconducting microresonator device for a typical KID, incorporating recent work on the power flow between superconductor quasiparticles and phonons. This model calculates the large-signal (changes in operating point) and small-signal behaviour of a device, allowing us to determine the effect of electrothermal feedback on device responsivity and noise characteristics under various operating conditions. We also investigate how thermally isolating the device from the bath, for example by designing the device on a membrane only connected to the bulk substrate by thin legs, affects device performance. We find that at a typical device operating point, positive electrothermal feedback reduces the effective thermal conductance from the superconductor quasiparticles to the bath, and so increases responsivity to signal (pair-breaking) power, increases noise from temperature fluctuations, and decreases the noise equivalent power (NEP). Similarly, increasing the thermal isolation of the device while keeping the quasiparticle temperature constant decreases the NEP, but also decreases the device response bandwidth.
Model for a pulsed terahertz quantum cascade laser under optical feedback.
Agnew, Gary; Grier, Andrew; Taimre, Thomas; Lim, Yah Leng; Bertling, Karl; Ikonić, Zoran; Valavanis, Alexander; Dean, Paul; Cooper, Jonathan; Khanna, Suraj P; Lachab, Mohammad; Linfield, Edmund H; Davies, A Giles; Harrison, Paul; Indjin, Dragan; Rakić, Aleksandar D
2016-09-05
Optical feedback effects in lasers may be useful or problematic, depending on the type of application. When semiconductor lasers are operated using pulsed-mode excitation, their behavior under optical feedback depends on the electronic and thermal characteristics of the laser, as well as the nature of the external cavity. Predicting the behavior of a laser under both optical feedback and pulsed operation therefore requires a detailed model that includes laser-specific thermal and electronic characteristics. In this paper we introduce such a model for an exemplar bound-to-continuum terahertz frequency quantum cascade laser (QCL), illustrating its use in a selection of pulsed operation scenarios. Our results demonstrate significant interplay between electro-optical, thermal, and feedback phenomena, and that this interplay is key to understanding QCL behavior in pulsed applications. Further, our results suggest that for many types of QCL in interferometric applications, thermal modulation via low duty cycle pulsed operation would be an alternative to commonly used adiabatic modulation.
ERIC Educational Resources Information Center
Cunningham, Thomas R.; Austin, John
2007-01-01
We evaluated the effects of a behavioral treatment on the safe passing of sharp instruments using the hands-free technique among hospital operating room personnel during surgical procedures. Treatment consisted of participative goal setting, task clarification, and feedback. The average percentage of sharp instruments passed safely increased from…
Accelerated Radiation-Damping for Increased Spin Equilibrium (ARISE)
Huang, Susie Y.; Witzel, Thomas; Wald, Lawrence L.
2008-01-01
Control of the longitudinal magnetization in fast gradient echo sequences is an important factor enabling the high efficiency of balanced Steady State Free Precession (bSSFP) sequences. We introduce a new method for accelerating the return of the longitudinal magnetization to the +z-axis that is independent of externally applied RF pulses and shows improved off-resonance performance. The Accelerated Radiation damping for Increased Spin Equilibrium (ARISE) method uses an external feedback circuit to strengthen the Radiation Damping (RD) field. The enhanced RD field rotates the magnetization back to the +z-axis at a rate faster than T1 relaxation. The method is characterized in gradient echo phantom imaging at 3T as a function of feedback gain, phase, and duration and compared with results from numerical simulations of the Bloch equations incorporating RD. A short period of feedback (10ms) during a refocused interval of a crushed gradient echo sequence allowed greater than 99% recovery of the longitudinal magnetization when very little T2 relaxation has time to occur. Appropriate applications might include improving navigated sequences. Unlike conventional flip-back schemes, the ARISE “flip-back” is generated by the spins themselves, thereby offering a potentially useful building block for enhancing gradient echo sequences. PMID:18956463
NASA Technical Reports Server (NTRS)
Cheng, D. Y.
1971-01-01
Converging, coaxial accelerator electrode configuration operates in vacuum as plasma gun. Plasma forms by periodic injections of high pressure gas that is ionized by electrical discharges. Deflagration mode of discharge provides acceleration, and converging contours of plasma gun provide focusing.
Feedback linearization for control of air breathing engines
NASA Technical Reports Server (NTRS)
Phillips, Stephen; Mattern, Duane
1991-01-01
The method of feedback linearization for control of the nonlinear nozzle and compressor components of an air breathing engine is presented. This method overcomes the need for a large number of scheduling variables and operating points to accurately model highly nonlinear plants. Feedback linearization also results in linear closed loop system performance simplifying subsequent control design. Feedback linearization is used for the nonlinear partial engine model and performance is verified through simulation.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Not Available
1992-06-01
Proposed action is to construct at BNL a 5,600-ft[sup 2] support building, install and operate a prototypic 200 MeV accelerator and a prototypic 700 MeV storage ring within, and to construct and operate a 15 kV substation to power the building. The accelerator and storage ring would comprise the x-ray lithography source or XLS.
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.
Examining the Effect of Feedback in Beginning L2 Composition
ERIC Educational Resources Information Center
Gascoigne, Carolyn
2004-01-01
Although L2 teachers tend to operate under the assumption that feedback on student compositions has a profound and positive effect on student revisions, few investigations have examined the results of teacher feedback. The present study, therefore, replicated a 1997 study by Ferris on the type and effect of feedback on advanced…
The Stratonovich formulation of quantum feedback network rules
NASA Astrophysics Data System (ADS)
Gough, John E.
2016-12-01
We express the rules for forming quantum feedback networks using the Stratonovich form of quantum stochastic calculus rather than the Itō or SLH (J. E. Gough and M. R. James, "Quantum feedback networks: Hamiltonian formulation," Commun. Math. Phys. 287, 1109 (2009), J. E. Gough and M. R. James, "The Series product and its application to quantum feedforward and feedback networks," IEEE Trans. Autom. Control 54, 2530 (2009)) form. Remarkably the feedback reduction rule implies that we obtain the Schur complement of the matrix of Stratonovich coupling operators where we short out the internal input/output coefficients.
The operation of the LHC accelerator complex (2/2)
Redaelli, Stefano
2018-05-23
These lectures will give an overview of what happens when the LHC is in running mode. They are aimed at students working on the LHC experiments, but all those who are curious about what happens behind the scenes of the LHC are welcomed. You will learn all you always wanted to know about the LHC, and never had the courage to ask! The only pre-requisite is a basic, college-level, knowledge of EM and of the principles that allow to steer charged beams. Topics covered will include, among others: - the description of the injector chain, from the generation of the protons, to the delivery of bunches to the LHC. - the discussion of the steps required to accelerate the beams in the LHC, to bring them into collision, and to control the luminosity at the interaction points. - the description of the monitoring tools available to the LHC operators, and an explanation of the various plots and panels that can be found on the LHC web pages
The operation of the LHC accelerator complex (1/2)
Redaelli, Stefano
2018-05-23
These lectures will give an overview of what happens when the LHC is in running mode. They are aimed at students working on the LHC experiments, but all those who are curious about what happens behind the scenes of the LHC are welcomed. You will learn all you always wanted to know about the LHC, and never had the courage to ask! The only pre-requisite is a basic, college-level, knowledge of EM and of the principles that allow to steer charged beams. Topics covered will include, among others: - the description of the injector chain, from the generation of the protons, to the delivery of bunches to the LHC. - the discussion of the steps required to accelerate the beams in the LHC, to bring them into collision, and to control the luminosity at the interaction points. - the description of the monitoring tools available to the LHC operators, and an explanation of the various plots and panels that can be found on the LHC web pages.
NASA Technical Reports Server (NTRS)
Broussard, J. R.; Halyo, N.
1984-01-01
This report contains the development of a digital outer-loop three dimensional radio navigation (3-D RNAV) flight control system for a small commercial jet transport. The outer-loop control system is designed using optimal stochastic limited state feedback techniques. Options investigated using the optimal limited state feedback approach include integrated versus hierarchical control loop designs, 20 samples per second versus 5 samples per second outer-loop operation and alternative Type 1 integration command errors. Command generator tracking techniques used in the digital control design enable the jet transport to automatically track arbitrary curved flight paths generated by waypoints. The performance of the design is demonstrated using detailed nonlinear aircraft simulations in the terminal area, frequency domain multi-input sigma plots, frequency domain single-input Bode plots and closed-loop poles. The response of the system to a severe wind shear during a landing approach is also presented.
Gong, Zhenxing; Li, Miaomiao; Qi, Yaoyuan; Zhang, Na
2017-01-01
In the formation mechanism of the feedback environment, the existing research pays attention to external feedback sources and regards individuals as objects passively accepting feedback. Thus, the external source fails to realize the individuals' need for feedback, and the feedback environment cannot provide them with useful information, leading to a feedback vacuum. The aim of this study is to examine the effect of feedback-seeking by different strategies on the supervisor-feedback environment through supervisor identification. The article consists of an empirical study with a sample of 264 employees in China; here, participants complete a series of questionnaires in three waves. After controlling for the effects of demography, the results indicate that supervisor identification partially mediates the relationship between feedback-seeking (including feedback monitoring and feedback inquiry) and the supervisor-feedback environment. Implications are also discussed.
Gong, Zhenxing; Li, Miaomiao; Qi, Yaoyuan; Zhang, Na
2017-01-01
In the formation mechanism of the feedback environment, the existing research pays attention to external feedback sources and regards individuals as objects passively accepting feedback. Thus, the external source fails to realize the individuals’ need for feedback, and the feedback environment cannot provide them with useful information, leading to a feedback vacuum. The aim of this study is to examine the effect of feedback-seeking by different strategies on the supervisor-feedback environment through supervisor identification. The article consists of an empirical study with a sample of 264 employees in China; here, participants complete a series of questionnaires in three waves. After controlling for the effects of demography, the results indicate that supervisor identification partially mediates the relationship between feedback-seeking (including feedback monitoring and feedback inquiry) and the supervisor-feedback environment. Implications are also discussed. PMID:28919872
NASA Technical Reports Server (NTRS)
Kuehn, T. J.; Nawrocki, P. M.
1978-01-01
It is suggested that federal programs for hastening the adoption of alternative energy sources must operate within the free market structure. Five phases of the free market commercialization process are described. Federal role possibilities include information dissemination and funding to stimulate private sector activities within these five phases, and federally sponsored procedures for accelerating commercialization of solar thermal small power systems are considered.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Jumpertz, L., E-mail: louise.jumpertz@telecom-paristech.fr; Alcatel Thales III-V Lab, Campus de Polytechnique, 1 avenue Augustin Fresnel, 91767 Palaiseau; Carras, M.
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.
NASA Astrophysics Data System (ADS)
Zheng, Yujin; Sekine, Takashi; Kurita, Takashi; Kato, Yoshinori; Kawashima, Toshiyuki
2018-03-01
We demonstrate continuous-wave dual-wavelength operation of a broad-area distributed feedback (DFB) laser diode with a single external-cavity configuration. This high-power DFB laser has a narrow bandwidth (<0.29 nm) and was used as a single-wavelength source. A volume Bragg grating was used as an output coupler for the external-cavity DFB laser to output another stable wavelength beam with a narrow bandwidth of 0.27 nm. A frequency difference for dual-wavelength operation of 0.88 THz was achieved and an output power of up to 415 mW was obtained. The external-cavity DFB laser showed a stable dual-wavelength operation over the practical current and temperature ranges.
Development of new S-band RF window for stable high-power operation in linear accelerator RF system
NASA Astrophysics Data System (ADS)
Joo, Youngdo; Lee, Byung-Joon; Kim, Seung-Hwan; Kong, Hyung-Sup; Hwang, Woonha; Roh, Sungjoo; Ryu, Jiwan
2017-09-01
For stable high-power operation, a new RF window is developed in the S-band linear accelerator (Linac) RF systems of the Pohang Light Source-II (PLS-II) and the Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL). The new RF window is designed to mitigate the strength of the electric field at the ceramic disk and also at the waveguide-cavity coupling structure of the conventional RF window. By replacing the pill-box type cavity in the conventional RF window with an overmoded cavity, the electric field component perpendicular to the ceramic disk that caused most of the multipacting breakdowns in the ceramic disk was reduced by an order of magnitude. The reduced electric field at the ceramic disk eliminated the Ti-N coating process on the ceramic surface in the fabrication procedure of the new RF window, preventing the incomplete coating from spoiling the RF transmission and lowering the fabrication cost. The overmoded cavity was coupled with input and output waveguides through dual side-wall coupling irises to reduce the electric field strength at the waveguide-cavity coupling structure and the possibility of mode competitions in the overmoded cavity. A prototype of the new RF window was fabricated and fully tested with the Klystron peak input power, pulse duration and pulse repetition rate of 75 MW, 4.5 μs and 10 Hz, respectively, at the high-power test stand. The first mass-produced new RF window installed in the PLS-II Linac is running in normal operation mode. No fault is reported to date. Plans are being made to install the new RF window to all S-band accelerator RF modules of the PLS-II and PAL-XFEL Linacs. This new RF window may be applied to the output windows of S-band power sources like Klystron as wells as the waveguide windows of accelerator facilities which operate in S-band.
RF power recovery feedback circulator
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.
Development of a subway operation incident delay model using accelerated failure time approaches.
Weng, Jinxian; Zheng, Yang; Yan, Xuedong; Meng, Qiang
2014-12-01
This study aims to develop a subway operational incident delay model using the parametric accelerated time failure (AFT) approach. Six parametric AFT models including the log-logistic, lognormal and Weibull models, with fixed and random parameters are built based on the Hong Kong subway operation incident data from 2005 to 2012, respectively. In addition, the Weibull model with gamma heterogeneity is also considered to compare the model performance. The goodness-of-fit test results show that the log-logistic AFT model with random parameters is most suitable for estimating the subway incident delay. First, the results show that a longer subway operation incident delay is highly correlated with the following factors: power cable failure, signal cable failure, turnout communication disruption and crashes involving a casualty. Vehicle failure makes the least impact on the increment of subway operation incident delay. According to these results, several possible measures, such as the use of short-distance and wireless communication technology (e.g., Wifi and Zigbee) are suggested to shorten the delay caused by subway operation incidents. Finally, the temporal transferability test results show that the developed log-logistic AFT model with random parameters is stable over time. Copyright © 2014 Elsevier Ltd. All rights reserved.
Acceleration ramps along high operating speed roadways.
DOT National Transportation Integrated Search
2010-11-01
Until recently, guidelines for the geometric design of acceleration lanes used for the : successful merge of an entering vehicle into a high-speed surface transportation system : through-traffic lane have been based upon concepts and vehicle characte...
Delayed feedback control in quantum transport.
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.
ACCELERATION RESPONSIVE SWITCH
Chabrek, A.F.; Maxwell, R.L.
1963-07-01
An acceleration-responsive device with dual channel capabilities whereby a first circuit is actuated upon attainment of a predetermined maximum acceleration level and when the acceleration drops to a predetermined minimum acceleriltion level another circuit is actuated is described. A fluid-damped sensing mass slidably mounted in a relatively frictionless manner on a shaft through the intermediation of a ball bushing and biased by an adjustable compression spring provides inertially operated means for actuating the circuits. (AEC)
Carbon Climate Feedbacks and Climate Sensitivity (Invited)
NASA Astrophysics Data System (ADS)
Fung, I.
2009-12-01
The Charney report (22 pages including bibliography and appendices) was written when atmospheric CO2 was 334 ppmv (1979). It estimates a climate sensitivity of 3 +/- 1.5C for a doubling of CO2, and points out the warming delay due to the slow penetration of heat into intermediate depths in the oceans and the decreasing capacity of the oceans to serve a CO2 sink. “We may not be given a warning until the CO2 loading is such that an appreciable climate change is inevitable. The equilibrium warming will eventually occur; it will merely have been postponed.” CO2 exceeded 385 ppmv in 2008, and the warning signs are now abundantly evident. One of the “slow” feedbacks not included in the Charney Report involves the interaction between the land carbon cycle and climate change. The carbon cycle on land is coupled to the water and energy cycles. This paper reviews positive and negative carbon-climate feedbacks associated with changes in the function and distribution of land ecosystems. These feedbacks, once in gear, will magnify climate sensitivity and accelerate global warming.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Not Available
1992-06-01
Proposed action is to construct at BNL a 5,600-ft{sup 2} support building, install and operate a prototypic 200 MeV accelerator and a prototypic 700 MeV storage ring within, and to construct and operate a 15 kV substation to power the building. The accelerator and storage ring would comprise the x-ray lithography source or XLS.
Kim, Kwang S; Max, Ludo
2014-01-01
To estimate the contributions of feedforward vs. feedback control systems in speech articulation, we analyzed the correspondence between initial and final kinematics in unperturbed tongue and jaw movements for consonant-vowel (CV) and vowel-consonant (VC) syllables. If movement extents and endpoints are highly predictable from early kinematic information, then the movements were most likely completed without substantial online corrections (feedforward control); if the correspondence between early kinematics and final amplitude or position is low, online adjustments may have altered the planned trajectory (feedback control) (Messier and Kalaska, 1999). Five adult speakers produced CV and VC syllables with high, mid, or low vowels while movements of the tongue and jaw were tracked electromagnetically. The correspondence between the kinematic parameters peak acceleration or peak velocity and movement extent as well as between the articulators' spatial coordinates at those kinematic landmarks and movement endpoint was examined both for movements across different target distances (i.e., across vowel height) and within target distances (i.e., within vowel height). Taken together, results suggest that jaw and tongue movements for these CV and VC syllables are mostly under feedforward control but with feedback-based contributions. One type of feedback-driven compensatory adjustment appears to regulate movement duration based on variation in peak acceleration. Results from a statistical model based on multiple regression are presented to illustrate how the relative strength of these feedback contributions can be estimated.
Voluntary modulation of anterior cingulate response to negative feedback.
Shane, Matthew S; Weywadt, Christina R
2014-01-01
Anterior cingulate and medial frontal cortex (dACC/mFC) response to negative feedback represents the actions of a generalized error-monitoring system critical for the management of goal-directed behavior. Magnitude of dACC/mFC response to negative feedback correlates with levels of post-feedback behavioral change, and with proficiency of operant learning processes. With this in mind, it follows that an ability to alter dACC/mFC response to negative feedback may lead to representative changes in operant learning proficiency. To this end, the present study investigated the extent to which healthy individuals would show modulation of their dACC/mFC response when instructed to try to either maximize or minimize their neural response to the presentation of contingent negative feedback. Participants performed multiple runs of a standard time-estimation task, during which they received feedback regarding their ability to accurately estimate a one-second duration. On Watch runs, participants were simply instructed to try to estimate as closely as possible the one second duration. On Increase and Decrease runs, participants performed the same task, but were instructed to "try to increase [decrease] their brain's response every time they received negative feedback". Results indicated that participants showed changes in dACC/mFC response under these differing instructional conditions: dACC/mFC activity following negative feedback was higher in the Increase condition, and dACC activity trended lower in the Decrease condition, compared to the Watch condition. Moreover, dACC activity correlated with post-feedback performance adjustments, and these adjustments were highest in the Increase condition. Potential implications for neuromodulation and facilitated learning are discussed.
New Transverse Bunch-by-Bunch Feedback System at TLS
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hu, K. H.; Kuo, C. H.; Hsu, S. Y.
2007-01-19
An FPGA based transverse bunch-by-bunch feedback system was implemented and commissioned to replace the existing analog transverse feedback system in order to suppress more effectively multi-bunch instabilities caused by the resistive wall of the vacuum chamber, cavity-like structures and ions related instability. This system replaces existing analog transverse feedback system to enlarge the tunability of the working point. Lower chromaticity is possible with feedback system that is very helpful for injection efficiency improvement. Top-up and high current operation is benefit for this upgrade. One feedback loop suppresses horizontal and vertical multi-bunch instabilities simultaneously. The clean and simple structure makes themore » system simple and reliable. This study also presents the preliminary result of commissioning the new transverse feedback system.« less
Fast global orbit feedback system in PLS-II
NASA Astrophysics Data System (ADS)
Lee, J.; Kim, C.; Kim, J. M.; Kim, K. R.; Lee, E. H.; Lee, J. W.; Lee, T. Y.; Park, C. D.; Shin, S.; Yoon, J. C.; Cho, W. S.; Park, G. S.; Kim, S. C.
2016-12-01
The transverse position of the electron beam in the Pohang Light Source-II is stabilized by the global orbit feedback system. A slow orbit feedback system has been operating at 2 Hz, and a fast orbit feedback (FOFB) system at 813 Hz was installed recently. This FOFB system consists of 96 electron-beam-position monitors, 48 horizontal fast correctors, 48 vertical fast correctors and Versa Module Europa bus control system. We present the design and implementation of the FOFB system and its test result. Simulation analysis is presented and future improvements are suggested.
NASA Technical Reports Server (NTRS)
Zaychik, Kirill; Cardullo, Frank; George, Gary; Kelly, Lon C.
2009-01-01
In order to use the Hess Structural Model to predict the need for certain cueing systems, George and Cardullo significantly expanded it by adding motion feedback to the model and incorporating models of the motion system dynamics, motion cueing algorithm and a vestibular system. This paper proposes a methodology to evaluate effectiveness of these innovations by performing a comparison analysis of the model performance with and without the expanded motion feedback. The proposed methodology is composed of two stages. The first stage involves fine-tuning parameters of the original Hess structural model in order to match the actual control behavior recorded during the experiments at NASA Visual Motion Simulator (VMS) facility. The parameter tuning procedure utilizes a new automated parameter identification technique, which was developed at the Man-Machine Systems Lab at SUNY Binghamton. In the second stage of the proposed methodology, an expanded motion feedback is added to the structural model. The resulting performance of the model is then compared to that of the original one. As proposed by Hess, metrics to evaluate the performance of the models include comparison against the crossover models standards imposed on the crossover frequency and phase margin of the overall man-machine system. Preliminary results indicate the advantage of having the model of the motion system and motion cueing incorporated into the model of the human operator. It is also demonstrated that the crossover frequency and the phase margin of the expanded model are well within the limits imposed by the crossover model.
Air Force research in human sensory feedback for telepresence
NASA Technical Reports Server (NTRS)
Julian, Ronald G.
1993-01-01
Telepresence operations require high quality information transfer between the human master and the remotely located slave. Present Air Force research focuses on the human aspects of the information needed to complete the control/feedback loop. Work in three key areas of human sensory feedback for manipulation of objects are described. Specific projects in each key area are outlined, including research tools (hardware), planned research, and test results. Nonmanipulative feedback technologies are mentioned to complete the advanced teleoperation discussions.
Electrorheological Fluid Based Force Feedback Device
NASA Technical Reports Server (NTRS)
Pfeiffer, Charles; Bar-Cohen, Yoseph; Mavroidis, Constantinos; Dolgin, Benjamin
1999-01-01
Parallel to the efforts to develop fully autonomous robots, it is increasingly being realized that there are applications where it is essential to have a fully controlled robot and "feel" its operating conditions, i.e. telepresence. This trend is a result of the increasing efforts to address tasks where humans can perform significantly better but, due to associated hazards, distance, physical limitations and other causes, only robots can be employed to perform these tasks. Such robots need to be assisted by a human that remotely controls the operation. To address the goal of operating robots as human surrogates, the authors launched a study of mechanisms that provide mechanical feedback. For this purpose, electrorheological fluids (ERF) are being investigated for the potential application as miniature haptic devices. This family of electroactive fluids has the property of changing the viscosity during electrical stimulation. Consequently, ERF can be used to produce force feedback haptic devices for tele-operated control of medical and space robotic systems. Forces applied at the robot end-effector due to a compliant environment are reflected to the user using an ERF device where a change in the system viscosity will occur proportionally to the transmitted force. Analytical model and control algorithms are being developed taking into account the non-linearities of these type of devices. This paper will describe the concept and the developed mechanism of ERF based force feedback. The test process and the physical properties of this device will be described and the results of preliminary tests will be presented.
Electrostatic Plasma Accelerator (EPA)
NASA Technical Reports Server (NTRS)
Brophy, John R.; Aston, Graeme
1989-01-01
The Electrostatic Plasma Accelerator (EPA) is a thruster concept which promises specific impulse levels between low power arcjets and those of the ion engine while retaining the relative simplicity of the arcjet. The EPA thruster produces thrust through the electrostatic acceleration of a moderately dense plasma. No accelerating electrodes are used and the specific impulse is a direct function of the applied discharge voltage and the propellant atomic mass. The goal of the present program is to demonstrate feasibility of the EPA thruster concept through experimental and theoretical investigations of the EPA acceleration mechanism and discharge chamber performance. Experimental investigations will include operating the test bed ion (TBI) engine as an EPA thruster and parametrically varying the thruster geometry and operating conditions to quantify the electrostatic plasma acceleration effect. The theoretical investigations will include the development of a discharge chamber model which describes the relationships between the engine size, plasma properties, and overall performance. For the EPA thruster to be a viable propulsion concept, overall thruster efficiencies approaching 30% with specific impulses approaching 1000 s must be achieved.
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.
NASA Astrophysics Data System (ADS)
Sledneva, A. S.; Kobets, V. V.
2017-06-01
The linear electron accelerator based on the LINAC - 800 accelerator imported from the Netherland is created at Joint Institute for Nuclear Research in the framework of the project on creation of the Testbed with an electron beam of a linear accelerator with an energy up to 250 MV. Currently two accelerator stations with a 60 MV energy of a beam are put in operation and the work is to put the beam through accelerating section of the third accelerator station. The electron beam with an energy of 23 MeV is used for testing the crystals (BaF2, CsI (native), and LYSO) in order to explore the opportunity to use them in particle detectors in experiments: Muon g-2, Mu2e, Comet, whose preparation requires a detailed study of the detectors properties such as their irradiation by the accelerator beams.
Comprehensive feedback on trainee surgeons’ non-technical skills
Dieckmann, Peter; Beier-Holgersen, Randi; Rosenberg, Jacob; Oestergaard, Doris
2015-01-01
Objectives This study aimed to explore the content of conversations, feedback style, and perceived usefulness of feedback to trainee surgeons when conversations were stimulated by a tool for assessing surgeons’ non-technical skills. Methods Trainee surgeons and their supervisors used the Non-Technical Skills for Surgeons in Denmark tool to stimulate feedback conversations. Audio recordings of post-operation feedback conversations were collected. Trainees and supervisors provided questionnaire responses on the usefulness and comprehensiveness of the feedback. The feedback conversations were qualitatively analyzed for content and feedback style. Usefulness was investigated using a scale from 1 to 5 and written comments were qualitatively analyzed. Results Six trainees and six supervisors participated in eight feedback conversations. Eighty questionnaires (response rate 83 percent) were collected from 13 trainees and 12 supervisors. Conversations lasted median eight (2-15) minutes. Supervisors used the elements and categories in the tool to structure the content of the conversations. Supervisors tended to talk about the trainees’ actions and their own frames rather than attempting to understand the trainees’ perceptions. Supervisors and trainees welcomed the feedback opportunity and agreed that the conversations were useful and comprehensive. Conclusions The content of the feedback conversations reflected the contents of the tool and the feedback was considered useful and comprehensive. However, supervisors talked primarily about their own frames, so in order for the feedback to reach its full potential, supervisors may benefit from training techniques to stimulate a deeper reflection among trainees. PMID:25602262
Single electron beam rf feedback free electron laser
Brau, C.A.; Stein, W.E.; Rockwood, S.D.
1981-02-11
A free electron laser system and electron beam system for a free electron laser which uses rf feedback to enhance efficiency are described. Rf energy is extracted from a single electron beam by decelerating cavities and energy is returned to accelerating cavities using rf returns, such as rf waveguides, rf feedthroughs, resonant feedthroughs, etc. This rf energy is added to rf klystron energy to reduce the required input energy and thereby enhance energy efficiency of the system.
Distributed force feedback in the spinal cord and the regulation of limb mechanics.
Nichols, T Richard
2018-03-01
This review is an update on the role of force feedback from Golgi tendon organs in the regulation of limb mechanics during voluntary movement. Current ideas about the role of force feedback are based on modular circuits linking idealized systems of agonists, synergists, and antagonistic muscles. In contrast, force feedback is widely distributed across the muscles of a limb and cannot be understood based on these circuit motifs. Similarly, muscle architecture cannot be understood in terms of idealized systems, since muscles cross multiple joints and axes of rotation and further influence remote joints through inertial coupling. It is hypothesized that distributed force feedback better represents the complex mechanical interactions of muscles, including the stresses in the musculoskeletal network born by muscle articulations, myofascial force transmission, and inertial coupling. Together with the strains of muscle fascicles measured by length feedback from muscle spindle receptors, this integrated proprioceptive feedback represents the mechanical state of the musculoskeletal system. Within the spinal cord, force feedback has excitatory and inhibitory components that coexist in various combinations based on motor task and integrated with length feedback at the premotoneuronal and motoneuronal levels. It is concluded that, in agreement with other investigators, autogenic, excitatory force feedback contributes to propulsion and weight support. It is further concluded that coexistent inhibitory force feedback, together with length feedback, functions to manage interjoint coordination and the mechanical properties of the limb in the face of destabilizing inertial forces and positive force feedback, as required by the accelerations and changing directions of both predator and prey.
Dynamics of nonlinear feedback control.
Snippe, H P; van Hateren, J H
2007-05-01
Feedback control in neural systems is ubiquitous. Here we study the mathematics of nonlinear feedback control. We compare models in which the input is multiplied by a dynamic gain (multiplicative control) with models in which the input is divided by a dynamic attenuation (divisive control). The gain signal (resp. the attenuation signal) is obtained through a concatenation of an instantaneous nonlinearity and a linear low-pass filter operating on the output of the feedback loop. For input steps, the dynamics of gain and attenuation can be very different, depending on the mathematical form of the nonlinearity and the ordering of the nonlinearity and the filtering in the feedback loop. Further, the dynamics of feedback control can be strongly asymmetrical for increment versus decrement steps of the input. Nevertheless, for each of the models studied, the nonlinearity in the feedback loop can be chosen such that immediately after an input step, the dynamics of feedback control is symmetric with respect to increments versus decrements. Finally, we study the dynamics of the output of the control loops and find conditions under which overshoots and undershoots of the output relative to the steady-state output occur when the models are stimulated with low-pass filtered steps. For small steps at the input, overshoots and undershoots of the output do not occur when the filtering in the control path is faster than the low-pass filtering at the input. For large steps at the input, however, results depend on the model, and for some of the models, multiple overshoots and undershoots can occur even with a fast control path.
Recent Advances in Understanding Particle Acceleration Processes in Solar Flares
NASA Astrophysics Data System (ADS)
Zharkova, V. V.; Arzner, K.; Benz, A. O.; Browning, P.; Dauphin, C.; Emslie, A. G.; Fletcher, L.; Kontar, E. P.; Mann, G.; Onofri, M.; Petrosian, V.; Turkmani, R.; Vilmer, N.; Vlahos, L.
2011-09-01
We review basic theoretical concepts in particle acceleration, with particular emphasis on processes likely to occur in regions of magnetic reconnection. Several new developments are discussed, including detailed studies of reconnection in three-dimensional magnetic field configurations (e.g., current sheets, collapsing traps, separatrix regions) and stochastic acceleration in a turbulent environment. Fluid, test-particle, and particle-in-cell approaches are used and results compared. While these studies show considerable promise in accounting for the various observational manifestations of solar flares, they are limited by a number of factors, mostly relating to available computational power. Not the least of these issues is the need to explicitly incorporate the electrodynamic feedback of the accelerated particles themselves on the environment in which they are accelerated. A brief prognosis for future advancement is offered.
Sirleo, Luigi; Innocenti, Massimo; Innocenti, Matteo; Civinini, Roberto; Carulli, Christian; Matassi, Fabrizio
2018-02-01
To evaluate the feedback from post-operative three-dimensional computed tomography (3D-CT) on femoral tunnel placement in the learning process, to obtain an anatomic anterior cruciate ligament (ACL) reconstruction. A series of 60 consecutive patients undergoing primary ACL reconstruction using autologous hamstrings single-bundle outside-in technique were prospectively included in the study. ACL reconstructions were performed by the same trainee-surgeon during his learning phase of anatomic ACL femoral tunnel placement. A CT scan with dedicated tunnel study was performed in all patients within 48 h after surgery. The data obtained from the CT scan were processed into a three-dimensional surface model, and a true medial view of the lateral femoral condyle was used for the femoral tunnel placement analysis. Two independent examiners analysed the tunnel placements. The centre of femoral tunnel was measured using a quadrant method as described by Bernard and Hertel. The coordinates measured were compared with anatomic coordinates values described in the literature [deep-to-shallow distance (X-axis) 28.5%; high-to-low distance (Y-axis) 35.2%]. Tunnel placement was evaluated in terms of accuracy and precision. After each ACL reconstruction, results were shown to the surgeon to receive an instant feedback in order to achieve accurate correction and improve tunnel placement for the next surgery. Complications and arthroscopic time were also recorded. Results were divided into three consecutive series (1, 2, 3) of 20 patients each. A trend to placing femoral tunnel slightly shallow in deep-to-shallow distance and slightly high in high-to-low distance was observed in the first and the second series. A progressive improvement in tunnel position was recorded from the first to second series and from the second to the third series. Both accuracy (+52.4%) and precision (+55.7%) increased from the first to the third series (p < 0.001). Arthroscopic time decreased from a mean of
Transverse impedances and collective instabilities in a heavy ion accelerator
NASA Astrophysics Data System (ADS)
Liu, J.; Yang, J. C.; Xia, J. W.; Yin, D. Y.; Shen, G. D.; Li, P.; Wu, B.; Ruan, S.; Zhao, H.; Wang, G.; Dong, Z. Q.; Wang, K. D.; Yao, L. P.
2018-06-01
Evaluation of transverse impedances and collective instabilities is important for determining whether a transverse feedback system or damping schemes should be prepared in the BRing (Booster Ring) at the HIAF (High Intensity Heavy-ion Accelerator Facility). In this paper, some dominant transverse impedances are estimated to build a transverse impedance model of the BRing. With this model, all potential transverse instabilities and their growth times or rates are analyzed by analytical methods or simulations, and the results agree with each other. The growth times of some instabilities are shorter than the duration times of corresponding manipulations, which shows transverse instabilities may have many detrimental impacts on the BRing. To cure the transverse instabilities, a transverse feedback system will be proposed in the design of the BRing. Besides, this paper not only shows the transverse instabilities in the BRing, but also provides the whole method for estimating them in the design of a new accelerator facility.
Space Acceleration Measurement System (SAMS)/Orbital Acceleration Research Experiment (OARE)
NASA Technical Reports Server (NTRS)
Hakimzadeh, Roshanak
1998-01-01
The Life and Microgravity Spacelab (LMS) payload flew on the Orbiter Columbia on mission STS-78 from June 20th to July 7th, 1996. The LMS payload on STS-78 was dedicated to life sciences and microgravity experiments. Two accelerometer systems managed by the NASA Lewis Research Center (LERC) flew to support these experiments, namely the Orbital Acceleration Research Experiment (OARE) and the Space Acceleration Measurements System (SAMS). In addition, the Microgravity Measurement Assembly (NOAA), managed by the European Space Research and Technology Center (ESA/ESTEC), and sponsored by NASA, collected acceleration data in support of the experiments on-board the LMS mission. OARE downlinked real-time quasi-steady acceleration data, which was provided to the investigators. The SAMS recorded higher frequency data on-board for post-mission analysis. The MMA downlinked real-time quasi-steady as well as higher frequency acceleration data, which was provided to the investigators. The Principal Investigator Microgravity Services (PIMS) project at NASA LERC supports principal investigators of microgravity experiments as they evaluate the effects of varying acceleration levels on their experiments. A summary report was prepared by PIMS to furnish interested experiment investigators with a guide to evaluate the acceleration environment during STS-78, and as a means of identifying areas which require further study. The summary report provides an overview of the STS-78 mission, describes the accelerometer systems flown on this mission, discusses some specific analyses of the accelerometer data in relation to the various activities which occurred during the mission, and presents plots resulting from these analyses as a snapshot of the environment during the mission. Numerous activities occurred during the STS-78 mission that are of interest to the low-gravity community. Specific activities of interest during this mission were crew exercise, radiator deployment, Vernier Reaction
Using on-line altered auditory feedback treating Parkinsonian speech
NASA Astrophysics Data System (ADS)
Wang, Emily; Verhagen, Leo; de Vries, Meinou H.
2005-09-01
Patients with advanced Parkinson's disease tend to have dysarthric speech that is hesitant, accelerated, and repetitive, and that is often resistant to behavior speech therapy. In this pilot study, the speech disturbances were treated using on-line altered feedbacks (AF) provided by SpeechEasy (SE), an in-the-ear device registered with the FDA for use in humans to treat chronic stuttering. Eight PD patients participated in the study. All had moderate to severe speech disturbances. In addition, two patients had moderate recurring stuttering at the onset of PD after long remission since adolescence, two had bilateral STN DBS, and two bilateral pallidal DBS. An effective combination of delayed auditory feedback and frequency-altered feedback was selected for each subject and provided via SE worn in one ear. All subjects produced speech samples (structured-monologue and reading) under three conditions: baseline, with SE without, and with feedbacks. The speech samples were randomly presented and rated for speech intelligibility goodness using UPDRS-III item 18 and the speaking rate. The results indicted that SpeechEasy is well tolerated and AF can improve speech intelligibility in spontaneous speech. Further investigational use of this device for treating speech disorders in PD is warranted [Work partially supported by Janus Dev. Group, Inc.].
Design of analog pixels front-end active feedback
NASA Astrophysics Data System (ADS)
Kmon, P.; Kadlubowski, L. A.; Kaczmarczyk, P.
2018-01-01
The paper presents the design of the active feedback used in a charge-sensitive amplifier. The predominant advantages of the presented circuit are its ability for setting wide range of pulse-time widths, small silicon area occupation and low power consumption. The feedback also allows sensor leakage current compensation and, thanks to an additional DC amplifier, it minimizes the output DC voltage variations, which is especially important in the DC coupled recording chain and for processes with limited supply voltage. The paper provides feedback description and its operation principle. The proposed circuit was designed in the CMOS 130nm technology.
Indirect human impacts turn off reciprocal feedbacks and decrease ecosystem resilience.
Bertness, Mark D; Brisson, Caitlin P; Crotty, Sinead M
2015-05-01
Creek bank salt marsh die-off is a conservation problem in New England, driven by predator depletion, which releases herbivores from consumer control. Many marshes, however, have begun to recover from die-off. We examined the hypothesis that the loss of the foundation species Spartina alterniflora has decreased facilitator populations, weakening reciprocal positive plant/animal feedbacks, resilience, and slowing recovery. Field surveys and experiments revealed that loss of Spartina leads to decreased biodiversity, and increased mortality and decreased growth of the ribbed mussel Geukensia demissa, a key facilitator of Spartina. Experimental addition of Geukensia facilitators to creek banks accelerated Spartina recovery, showing that their loss limits recovery and the reciprocal feedbacks that drive community resilience. Reciprocal positive feedbacks involving foundation species, often lost to human impacts, may be a common, but generally overlooked mechanism of ecosystem resilience, making their reestablishment a valuable restoration tool.
Feedback Valence Affects Auditory Perceptual Learning Independently of Feedback Probability
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. PMID:25946173
Role of failure-mechanism identification in accelerated testing
NASA Technical Reports Server (NTRS)
Hu, J. M.; Barker, D.; Dasgupta, A.; Arora, A.
1993-01-01
Accelerated life testing techniques provide a short-cut method to investigate the reliability of electronic devices with respect to certain dominant failure mechanisms that occur under normal operating conditions. However, accelerated tests have often been conducted without knowledge of the failure mechanisms and without ensuring that the test accelerated the same mechanism as that observed under normal operating conditions. This paper summarizes common failure mechanisms in electronic devices and packages and investigates possible failure mechanism shifting during accelerated testing.
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.
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.
Leach, D J; Jackson, P R; Wall, T D
2001-07-15
An empowerment initiative involving enhanced fault-management responsibility for operators of complex technology had not led to expected increases in performance, and investigations suggested that this was due to a lack of appropriate feedback. Thus, a feedback intervention was designed to provide specific, timely feedback on operator-correctable faults. It was hypothesized that the intervention would increase operator self-reliance in operating complex technology and promote system performance. Moreover, given the feedback was continuous from the point of intervention, it was predicted that gains would increase over time. Time series analysis of data on engineer call-outs (self-reliance) and machine utilization (performance) showed clear positive effects of the feedback intervention, with call-outs also showing progressive improvement. Self-report data showed no change over time in motivation, but an increase in knowledge dissemination and a reduction in the likelihood of making expensive mistakes. There were no detrimental effects on operator well being. Implications for theory and practice in the management of complex technology are discussed.
Accelerators Beyond The Tevatron?
NASA Astrophysics Data System (ADS)
Lach, Joseph
2010-07-01
Following the successful operation of the Fermilab superconducting accelerator three new higher energy accelerators were planned. They were the UNK in the Soviet Union, the LHC in Europe, and the SSC in the United States. All were expected to start producing physics about 1995. They did not. Why?.
Reversed field pinch operation with intelligent shell feedback control in EXTRAP T2R
NASA Astrophysics Data System (ADS)
Brunsell, P. R.; Kuldkepp, M.; Menmuir, S.; Cecconello, M.; Hedqvist, A.; Yadikin, D.; Drake, J. R.; Rachlew, E.
2006-11-01
Discharges in the thin shell reversed field pinch (RFP) device EXTRAP T2R without active feedback control are characterized by growth of non-resonant m = 1 unstable resistive wall modes (RWMs) in agreement with linear MHD theory. Resonant m = 1 tearing modes (TMs) exhibit initially fast rotation and the associated perturbed radial fields at the shell are small, but eventually TMs wall-lock and give rise to a growing radial field. The increase in the radial field at the wall due to growing RWMs and wall-locked TMs is correlated with an increase in the toroidal loop voltage, which leads to discharge termination after 3-4 wall times. An active magnetic feedback control system has been installed in EXTRAP T2R. A two-dimensional array of 128 active saddle coils (pair-connected into 64 independent m = 1 coils) is used with intelligent shell feedback control to suppress the m = 1 radial field at the shell. With feedback control, active stabilization of the full toroidal spectrum of 16 unstable m = 1 non-resonant RWMs is achieved, and TM wall locking is avoided. A three-fold extension of the pulse length, up to the power supply limit, is observed. Intelligent shell feedback control is able to maintain the plasma equilibrium for 10 wall times, with plasma confinement parameters sustained at values comparable to those obtained in thick shell devices of similar size.
Whitney, Paul; Hinson, John M.; Jackson, Melinda L.; Van Dongen, Hans P.A.
2015-01-01
or because the feedback is not cognitively bound with the choice. This has important implications for understanding and managing sleep loss-induced cognitive impairment in emergency response, disaster management, military operations, and other dynamic real-world settings with uncertain outcomes and imperfect information. Citation: Whitney P, Hinson JM, Jackson ML, Van Dongen HPA. Feedback blunting: total sleep deprivation impairs decision making that requires updating based on feedback. SLEEP 2015;38(5):745–754. PMID:25515105
Apparatus for providing vibrotactile sensory substitution of force feedback
NASA Technical Reports Server (NTRS)
Massimino, Michael J. (Inventor); Sheridan, Thomas B. (Inventor); Patrick, Nicholas J. M. (Inventor)
1997-01-01
A feedback apparatus for an operator to control an effector that is remote from the operator to interact with a remote environment has a local input device to be manipulated by the operator. Sensors in the effector's environment are capable of sensing the amplitude of forces arising between the effector and its environment, the direction of application of such forces, or both amplitude and direction. A feedback signal corresponding to such a component of the force, is generated and transmitted to the environment of the operator. The signal is transduced into a vibrotactile sensory substitution signal to which the operator is sensitive. Vibration producing apparatus present the vibrotactile signal to the operator. The full range of the force amplitude may be represented by a single, mechanical vibrator. Vibrotactile display elements can be located on the operator's limbs, such as on the hand, fingers, arms, legs, feet, etc. The location of the application of the force may also be specified by the location of a vibrotactile display on the operator's body. Alternatively, the location may be specified by the frequency of a vibrotactile signal.
The purpose of this SOP is to describe the coding strategy for the Questionnaire Feedback form. This Questionnaire Feedback form was developed for use during the Arizona NHEXAS project and the "Border" study. Keywords: data; coding; questionnaire feedback form.
The National Hu...
An Endogenous Accelerator for Viral Gene Expression Confers a Fitness Advantage
Teng, Melissa W.; Bolovan-Fritts, Cynthia; Dar, Roy D.; Womack, Andrew; Simpson, Michael L.; Shenk, Thomas; Weinberger, Leor S.
2012-01-01
Many signaling circuits face a fundamental tradeoff between accelerating their response speed while maintaining final levels below a cytotoxic threshold. Here, we describe a transcriptional circuitry that dynamically converts signaling inputs into faster rates without amplifying final equilibrium levels. Using time-lapse microscopy, we find that transcriptional activators accelerate human cytomegalovirus (CMV) gene expression in single cells without amplifying steady-state expression levels, and this acceleration generates a significant replication advantage. We map the accelerator to a highly self-cooperative transcriptional negative-feedback loop (Hill coefficient ~ 7) generated by homo-multimerization of the virus’s essential transactivator protein IE2 at nuclear PML bodies. Eliminating the IE2-accelerator circuit reduces transcriptional strength through mislocalization of incoming viral genomes away from PML bodies and carries a heavy fitness cost. In general, accelerators may provide a mechanism for signal-transduction circuits to respond quickly to external signals without increasing steady-state levels of potentially cytotoxic molecules. PMID:23260143
Feedback control for manipulating magnetization in spin-exchange optical pumping system
NASA Astrophysics Data System (ADS)
Zhang, Ke; Li, Jun; Jiang, Min; Zhao, Nan; Peng, XinHua
2018-08-01
Control of magnetization plays an important role in the scientific and technological field of manipulating spin systems. In this work, we study the problem of manipulating nuclear magnetization in the spin-exchange optical pumping system, including accelerating the recovery of nuclear polarization and fixing it on a specific desired state. A real-time feedback control strategy is exploited here. We have also done some numerical simulations, with the results clearly demonstrating the effectiveness of our method, that the nuclear magnetization is able to be driven towards the equilibrium state at a much faster speed and also can be stabilized to a target state. We expect that our feedback control method can find applications in gyro experiments.
General, database-driven fast-feedback system for the Stanford Linear Collider
DOE Office of Scientific and Technical Information (OSTI.GOV)
Rouse, F.; Allison, S.; Castillo, S.
A new feedback system has been developed for stabilizing the SLC beams at many locations. The feedback loops are designed to sample and correct at the 60 Hz repetition rate of the accelerator. Each loop can be distributed across several of the standard 80386 microprocessors which control the SLC hardware. A new communications system, KISNet, has been implemented to pass signals between the microprocessors at this rate. The software is written in a general fashion using the state space formalism of digital control theory. This allows a new loop to be implemented by just setting up the online database andmore » perhaps installing a communications link. 3 refs., 4 figs.« less
Feedforward-feedback control of dissolved oxygen concentration in a predenitrification system.
Yong, Ma; Yongzhen, Peng; Shuying, Wang
2005-07-01
As the largest single energy-consuming component in most biological wastewater treatment systems, aeration control is of great interest from the point of view of saving energy and improving wastewater treatment plant efficiency. In this paper, three different strategies, including conventional constant dissolved oxygen (DO) set-point control, cascade DO set-point control, and feedforward-feedback DO set-point control were evaluated using the denitrification layout of the IWA simulation benchmark. Simulation studies showed that the feedforward-feedback DO set-point control strategy was better than the other control strategies at meeting the effluent standards and reducing operational costs. The control strategy works primarily by feedforward control based on an ammonium sensor located at the head of the aerobic process. It has an important advantage over effluent measurements in that there is no (or only a very short) time delay for information; feedforward control was combined with slow feedback control to compensate for model approximations. The feedforward-feedback DO control was implemented in a lab-scale wastewater treatment plant for a period of 60 days. Compared to operation with constant DO concentration, the required airflow could be reduced by up to 8-15% by employing the feedforward-feedback DO-control strategy, and the effluent ammonia concentration could be reduced by up to 15-25%. This control strategy can be expected to be accepted by the operating personnel in wastewater treatment plants.
Accelerator diagnosis and control by Neural Nets
DOE Office of Scientific and Technical Information (OSTI.GOV)
Spencer, J.E.
1989-01-01
Neural Nets (NN) have been described as a solution looking for a problem. In the last conference, Artificial Intelligence (AI) was considered in the accelerator context. While good for local surveillance and control, its use for large complex systems (LCS) was much more restricted. By contrast, NN provide a good metaphor for LCS. It can be argued that they are logically equivalent to multi-loop feedback/forward control of faulty systems, and therefore provide an ideal adaptive control system. Thus, where AI may be good for maintaining a 'golden orbit,' NN should be good for obtaining it via a quantitative approach tomore » 'look and adjust' methods like operator tweaking which use pattern recognition to deal with hardware and software limitations, inaccuracies or errors as well as imprecise knowledge or understanding of effects like annealing and hysteresis. Further, insights from NN allow one to define feasibility conditions for LCS in terms of design constraints and tolerances. Hardware and software implications are discussed and several LCS of current interest are compared and contrasted. 15 refs., 5 figs.« less
Beam acceleration through proton radio frequency quadrupole accelerator in BARC
NASA Astrophysics Data System (ADS)
Bhagwat, P. V.; Krishnagopal, S.; Mathew, J. V.; Singh, S. K.; Jain, P.; Rao, S. V. L. S.; Pande, M.; Kumar, R.; Roychowdhury, P.; Kelwani, H.; Rama Rao, B. V.; Gupta, S. K.; Agarwal, A.; Kukreti, B. M.; Singh, P.
2016-05-01
A 3 MeV proton Radio Frequency Quadrupole (RFQ) accelerator has been designed at the Bhabha Atomic Research Centre, Mumbai, India, for the Low Energy High Intensity Proton Accelerator (LEHIPA) programme. The 352 MHz RFQ is built in 4 segments and in the first phase two segments of the LEHIPA RFQ were commissioned, accelerating a 50 keV, 1 mA pulsed proton beam from the ion source, to an energy of 1.24 MeV. The successful operation of the RFQ gave confidence in the physics understanding and technology development that have been achieved, and indicate that the road forward can now be traversed rather more quickly.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Mcguckin, Theodore
2008-10-01
The Jefferson Lab Accelerator Controls Environment (ACE) was predominantly based on the HP-UX Unix platform from 1987 through the summer of 2004. During this period the Accelerator Machine Control Center (MCC) underwent a major renovation which included introducing Redhat Enterprise Linux machines, first as specialized process servers and then gradually as general login servers. As computer programs and scripts required to run the accelerator were modified, and inherent problems with the HP-UX platform compounded, more development tools became available for use with Linux and the MCC began to be converted over. In May 2008 the last HP-UX Unix login machinemore » was removed from the MCC, leaving only a few Unix-based remote-login servers still available. This presentation will explore the process of converting an operational Control Room environment from the HP-UX to Linux platform as well as the many hurdles that had to be overcome throughout the transition period (including a discussion of« less
ELECTROSTATIC ACCELERATORS (in French)
DOE Office of Scientific and Technical Information (OSTI.GOV)
Gerbier, R.
1962-04-01
The various methods presently in use for producing the continuous high voltage necessary for the operation of electrostatic accelerators are reviewed. The methods considered are voltage multiplier units (Greinacher and Morganstern types) and electrostatic instruments (Van de Graaff and Trump machines and Felici rotnting cylinder instruments). The electrostatic accelerators used at Grenoble which give currents of several milliamperes at voltages up to 1.2 Mv are described. In this energy region electron accelerators and neutron generators offer very interesting possibilities. (auth)
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…
Illinois Accelerator Research Center
Kroc, Thomas K.; Cooper, Charlie A.
2017-10-26
The Illinois Accelerator Research Center (IARC) hosts a new accelerator development program at Fermi National Accelerator Laboratory. IARC provides access to Fermi's state-of-the-art facilities and technologies for research, development and industrialization of particle accelerator technology. In addition to facilitating access to available existing Fermi infrastructure, the IARC Campus has a dedicated 36,000 ft2 heavy assembly building (HAB) with all the infrastructure needed to develop, commission and operate new accelerators. Connected to the HAB is a 47,000 ft Office, Technology and Engineering (OTE) building, paid for by the state, that has office, meeting, and light technical space. The OTE building, whichmore » contains the Accelerator Physics Center, and nearby Accelerator and Technical divisions provide IARC collaborators with unique access to world class expertise in a wide array of accelerator technologies. Finally, at IARC scientists and engineers from Fermilab and academia work side by side with industrial partners to develop breakthroughs in accelerator science and translate them into applications for the nation's health, wealth and security.« less
Illinois Accelerator Research Center
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kroc, Thomas K.; Cooper, Charlie A.
The Illinois Accelerator Research Center (IARC) hosts a new accelerator development program at Fermi National Accelerator Laboratory. IARC provides access to Fermi's state-of-the-art facilities and technologies for research, development and industrialization of particle accelerator technology. In addition to facilitating access to available existing Fermi infrastructure, the IARC Campus has a dedicated 36,000 ft2 heavy assembly building (HAB) with all the infrastructure needed to develop, commission and operate new accelerators. Connected to the HAB is a 47,000 ft Office, Technology and Engineering (OTE) building, paid for by the state, that has office, meeting, and light technical space. The OTE building, whichmore » contains the Accelerator Physics Center, and nearby Accelerator and Technical divisions provide IARC collaborators with unique access to world class expertise in a wide array of accelerator technologies. Finally, at IARC scientists and engineers from Fermilab and academia work side by side with industrial partners to develop breakthroughs in accelerator science and translate them into applications for the nation's health, wealth and security.« less
Illinois Accelerator Research Center
NASA Astrophysics Data System (ADS)
Kroc, Thomas K.; Cooper, Charlie A.
The Illinois Accelerator Research Center (IARC) hosts a new accelerator development program at Fermi National Accelerator Laboratory. IARC provides access to Fermi's state-of-the-art facilities and technologies for research, development and industrialization of particle accelerator technology. In addition to facilitating access to available existing Fermi infrastructure, the IARC Campus has a dedicated 36,000 ft2 Heavy Assembly Building (HAB) with all the infrastructure needed to develop, commission and operate new accelerators. Connected to the HAB is a 47,000 ft2 Office, Technology and Engineering (OTE) building, paid for by the state, that has office, meeting, and light technical space. The OTE building, which contains the Accelerator Physics Center, and nearby Accelerator and Technical divisions provide IARC collaborators with unique access to world class expertise in a wide array of accelerator technologies. At IARC scientists and engineers from Fermilab and academia work side by side with industrial partners to develop breakthroughs in accelerator science and translate them into applications for the nation's health, wealth and security.
Effect of biased feedback on motor imagery learning in BCI-teleoperation system.
Alimardani, Maryam; Nishio, Shuichi; Ishiguro, Hiroshi
2014-01-01
Feedback design is an important issue in motor imagery BCI systems. Regardless, to date it has not been reported how feedback presentation can optimize co-adaptation between a human brain and such systems. This paper assesses the effect of realistic visual feedback on users' BCI performance and motor imagery skills. We previously developed a tele-operation system for a pair of humanlike robotic hands and showed that BCI control of such hands along with first-person perspective visual feedback of movements can arouse a sense of embodiment in the operators. In the first stage of this study, we found that the intensity of this ownership illusion was associated with feedback presentation and subjects' performance during BCI motion control. In the second stage, we probed the effect of positive and negative feedback bias on subjects' BCI performance and motor imagery skills. Although the subject specific classifier, which was set up at the beginning of experiment, detected no significant change in the subjects' online performance, evaluation of brain activity patterns revealed that subjects' self-regulation of motor imagery features improved due to a positive bias of feedback and a possible occurrence of ownership illusion. Our findings suggest that in general training protocols for BCIs, manipulation of feedback can play an important role in the optimization of subjects' motor imagery skills.
Application of simple negative feedback model for avalanche photodetectors investigation
NASA Astrophysics Data System (ADS)
Kushpil, V. V.
2009-10-01
A simple negative feedback model based on Miller's formula is used to investigate the properties of Avalanche Photodetectors (APDs). The proposed method can be applied to study classical APD as well as new type of devices, which are operating in the Internal Negative Feedback (INF) regime. The method shows a good sensitivity to technological APD parameters making it possible to use it as a tool to analyse various APD parameters. It also allows better understanding of the APD operation conditions. The simulations and experimental data analysis for different types of APDs are presented.
Superconducting traveling wave accelerators
DOE Office of Scientific and Technical Information (OSTI.GOV)
Farkas, Z.D.
1984-11-01
This note considers the applicability of superconductivity to traveling wave accelerators. Unlike CW operation of a superconducting standing wave or circulating wave accelerator section, which requires improvement factors (superconductor conductivity divided by copper conductivity) of about 10/sup 6/ in order to be of practical use, a SUperconducting TRaveling wave Accelerator, SUTRA, operating in the pulsed mode requires improvement factors as low as about 10/sup 3/, which are attainable with niobium or lead at 4.2K, the temperature of liquid helium at atmospheric pressure. Changing from a copper traveling wave accelerator to SUTRA achieves the following. (1) For a given gradient SUTRAmore » reduces the peak and average power requirements typically by a factor of 2. (2) SUTRA reduces the peak power still further because it enables us to increase the filling time and thus trade pulse width for gradient. (3) SUTRA makes possible a reasonably long section at higher frequencies. (4) SUTRA makes possible recirculation without additional rf average power. 8 references, 6 figures, 1 table.« less
Scale-by-scale contributions to Lagrangian particle acceleration
NASA Astrophysics Data System (ADS)
Lalescu, Cristian C.; Wilczek, Michael
2017-11-01
Fluctuations on a wide range of scales in both space and time are characteristic of turbulence. Lagrangian particles, advected by the flow, probe these fluctuations along their trajectories. In an effort to isolate the influence of the different scales on Lagrangian statistics, we employ direct numerical simulations (DNS) combined with a filtering approach. Specifically, we study the acceleration statistics of tracers advected in filtered fields to characterize the smallest temporal scales of the flow. Emphasis is put on the acceleration variance as a function of filter scale, along with the scaling properties of the relevant terms of the Navier-Stokes equations. We furthermore discuss scaling ranges for higher-order moments of the tracer acceleration, as well as the influence of the choice of filter on the results. Starting from the Lagrangian tracer acceleration as the short time limit of the Lagrangian velocity increment, we also quantify the influence of filtering on Lagrangian intermittency. Our work complements existing experimental results on intermittency and accelerations of finite-sized, neutrally-buoyant particles: for the passive tracers used in our DNS, feedback effects are neglected such that the spatial averaging effect is cleanly isolated.
Kamali, Dariush; Illing, Jan
2018-01-01
Objective To identify the perception of positive feedback (PF) and negative feedback (NF) provided by trainers in the operating theatre on surgical trainees' confidence and well-being. Design Narrative interview study. Setting Twelve hospitals that form part of one deanery within the UK. Participants Maximum variation sampling of 15 higher general surgical trainees provided insight into how PF and NF from trainers in the operating theatre affect confidence and well-being. Methods Narrative telephone interviews were conducted with general surgical trainees between April and June 2016. All interviews were recorded, transcribed and anonymised. Transcriptions were analysed using the five-step framework analysis by two independent researchers. Results Fifteen trainees (age 28–38 years) were interviewed (median interview time: 29 min). Thematic framework analysis identified nine themes within the data. PF, which included corrective feedback, helped the trainees to relax and seemed to enhance their operative performance. All trainees reported significant and unjustified NF, some of which would be defined as undermining and bullying. Many believed this to have a negative impact on their training with minimal educational benefit. Many trainees felt NF adversely affected their performance in the operating theatre with some expressing a wish to leave the profession as a consequence. Conclusion Both PF and NF exist in the operating theatre. Both have an important influence on the trainee, their performance and career. PF, if specific, helped aid progression of learning, increased motivation and performance of surgical trainees. In contrast, NF was perceived to have detrimental effects on trainees’ performance and their well-being and, in some, introduced a desire to pursue an alternative career. PMID:29440141
Dynamic imperfections and optimized feedback design in the Compact Linear Collider main linac
NASA Astrophysics Data System (ADS)
Eliasson, Peder
2008-05-01
The Compact Linear Collider (CLIC) main linac is sensitive to dynamic imperfections such as element jitter, injected beam jitter, and ground motion. These effects cause emittance growth that, in case of ground motion, has to be counteracted by a trajectory feedback system. The feedback system itself will, due to jitter effects and imperfect beam position monitors (BPMs), indirectly cause emittance growth. Fast and accurate simulations of both the direct and indirect effects are desirable, but due to the many elements of the CLIC main linac, simulations may become very time consuming. In this paper, an efficient way of simulating linear (or nearly linear) dynamic effects is described. The method is also shown to facilitate the analytic determination of emittance growth caused by the different dynamic imperfections while using a trajectory feedback system. Emittance growth expressions are derived for quadrupole, accelerating structure, and beam jitter, for ground motion, and for noise in the feedback BPMs. Finally, it is shown how the method can be used to design a feedback system that is optimized for the optics of the machine and the ground motion spectrum of the particular site. This feedback system gives an emittance growth rate that is approximately 10 times lower than that of traditional trajectory feedbacks. The robustness of the optimized feedback system is studied for a number of additional imperfections, e.g., dipole corrector imperfections and faulty knowledge about the machine optics, with promising results.
Corticocortical feedback increases the spatial extent of normalization.
Nassi, Jonathan J; Gómez-Laberge, Camille; Kreiman, Gabriel; Born, Richard T
2014-01-01
Normalization has been proposed as a canonical computation operating across different brain regions, sensory modalities, and species. It provides a good phenomenological description of non-linear response properties in primary visual cortex (V1), including the contrast response function and surround suppression. Despite its widespread application throughout the visual system, the underlying neural mechanisms remain largely unknown. We recently observed that corticocortical feedback contributes to surround suppression in V1, raising the possibility that feedback acts through normalization. To test this idea, we characterized area summation and contrast response properties in V1 with and without feedback from V2 and V3 in alert macaques and applied a standard normalization model to the data. Area summation properties were well explained by a form of divisive normalization, which computes the ratio between a neuron's driving input and the spatially integrated activity of a "normalization pool." Feedback inactivation reduced surround suppression by shrinking the spatial extent of the normalization pool. This effect was independent of the gain modulation thought to mediate the influence of contrast on area summation, which remained intact during feedback inactivation. Contrast sensitivity within the receptive field center was also unaffected by feedback inactivation, providing further evidence that feedback participates in normalization independent of the circuit mechanisms involved in modulating contrast gain and saturation. These results suggest that corticocortical feedback contributes to surround suppression by increasing the visuotopic extent of normalization and, via this mechanism, feedback can play a critical role in contextual information processing.
Whitney, Paul; Hinson, John M; Jackson, Melinda L; Van Dongen, Hans P A
2015-05-01
To better understand the sometimes catastrophic effects of sleep loss on naturalistic decision making, we investigated effects of sleep deprivation on decision making in a reversal learning paradigm requiring acquisition and updating of information based on outcome feedback. Subjects were randomized to a sleep deprivation or control condition, with performance testing at baseline, after 2 nights of total sleep deprivation (or rested control), and following 2 nights of recovery sleep. Subjects performed a decision task involving initial learning of go and no go response sets followed by unannounced reversal of contingencies, requiring use of outcome feedback for decisions. A working memory scanning task and psychomotor vigilance test were also administered. Six consecutive days and nights in a controlled laboratory environment with continuous behavioral monitoring. Twenty-six subjects (22-40 y of age; 10 women). Thirteen subjects were randomized to a 62-h total sleep deprivation condition; the others were controls. Unlike controls, sleep deprived subjects had difficulty with initial learning of go and no go stimuli sets and had profound impairment adapting to reversal. Skin conductance responses to outcome feedback were diminished, indicating blunted affective reactions to feedback accompanying sleep deprivation. Working memory scanning performance was not significantly affected by sleep deprivation. And although sleep deprived subjects showed expected attentional lapses, these could not account for impairments in reversal learning decision making. Sleep deprivation is particularly problematic for decision making involving uncertainty and unexpected change. Blunted reactions to feedback while sleep deprived underlie failures to adapt to uncertainty and changing contingencies. Thus, an error may register, but with diminished effect because of reduced affective valence of the feedback or because the feedback is not cognitively bound with the choice. This has important
DOE Office of Scientific and Technical Information (OSTI.GOV)
Monazam, E.R.; Shadle, L.J.
2008-11-05
In commercial circulating fluidized bed (CFB) processes the acceleration zone greatly contributes to solids mixing, gas and solids dispersion, and particle residence times. A new analysis was developed to describe the relative gas-solids concentration in the acceleration region of a transport system with air as the fluidizing agent for Geldart-type B particles. A theoretical expression was derived from a drag relationship and momentum and continuity equations to describe the evolution of the gas-solids profile along the axial direction. The acceleration zone was characterized using nondimensional analysis of the continuum equations (balances of masses and momenta) that described multiphase flows. Inmore » addition to acceleration length, the boundary condition for the solids fraction at the bottom of the riser and the fully developed regions were measured using an industrial scale CFB of 0.3 m diameter and 15 m tall. The operating factors affecting the flow development in the acceleration region were determined for three materials of various sizes and densities in core annular and dilute regimes of the riser. Performance data were taken from statistically designed experiments over a wide range of Fr (0.5-39), Re (8-600), Ar (29-3600), load ratio (0.2-28), riser to particle diameter ratio (375-5000), and gas to solids density ratio (138-1381). In this one-dimensional system of equations, velocities and solid fractions were assumed to be constant over any cross section. The model and engineering correlations were compared with literature expressions to assess their validity and range of applicability. These expressions can be used as tools for simulation and design of a CFB riser and can also be easily coupled to a kinetics model for process simulation.« less
The effect of experience, simulator-training and biometric feedback on manual ventilation technique.
Lewis, Rebecca; Sherfield, Cerrie A; Fellows, Christopher R; Burrow, Rachel; Young, Iain; Dugdale, Alex
2017-05-01
To determine the frequency of provision and main providers (veterinary surgeons, nurses or trainees) of manual ventilation in UK veterinary practices. Furthermore, to determine the variation in peak inspiratory (inflation) pressure (PIP), applied to a lung model during manual ventilation, by three different groups of operators (inexperienced, experienced and specialist), before and after training. Questionnaire survey, lung model simulator development and prospective testing. Postal questionnaires were sent to 100 randomly selected veterinary practices. The lung model simulator was manually ventilated in a staged process over 3 weeks, with and without real-time biometric feedback (PIP display), by three groups of volunteer operators: inexperienced, experienced and specialist. The questionnaires determined that veterinary nurses were responsible for providing the majority of manual ventilation in veterinary practices, mainly drawing on theoretical knowledge rather than any specific training. Thoracic surgery and apnoea were the main reasons for provision of manual ventilation. Specialists performed well when manually ventilating the lung model, regardless of feedback training. Both inexperienced and experienced operators showed significant improvement in technique when using the feedback training tool: variation in PIP decreased significantly until operators provided manual ventilation at PIPs within the defined optimum range. Preferences for different forms of feedback (graphical, numerical or scale display), revealed that the operators' choice was not always the method which gave least variation in PIP. This study highlighted a need for training in manual ventilation at an early stage in veterinary and veterinary nursing careers and demonstrated how feedback is important in the process of experiential learning. A manometer device which can provide immediate feedback during training, or indeed in a real clinical setting, should improve patient safety. Copyright
ERIC Educational Resources Information Center
Funk, Mathias; van Diggelen, Migchiel
2017-01-01
In this paper, the authors describe how a study of a large database of written university teacher feedback in the department of Industrial Design led to the development of a new conceptual framework for feedback and the design of a new feedback tool. This paper focuses on the translation of related work in the area of feedback mechanisms for…
Accelerated aging tests on ENEA-ASE solar coating for receiver tube suitable to operate up to 550 °C
NASA Astrophysics Data System (ADS)
Antonaia, A.; D'Angelo, A.; Esposito, S.; Addonizio, M. L.; Castaldo, A.; Ferrara, M.; Guglielmo, A.; Maccari, A.
2016-05-01
A patented solar coating for evacuated receiver, based on innovative graded WN-AlN cermet layer, has been optically designed and optimized to operate at high temperature with high performance and high thermal stability. This solar coating, being designed to operate in solar field with molten salt as heat transfer fluid, has to be thermally stable up to the maximum temperature of 550 °C. With the aim of determining degradation behaviour and lifetime prediction of the solar coating, we chose to monitor the variation of the solar absorptance αs after each thermal annealing cycle carried out at accelerated temperatures under vacuum. This prediction method was coupled with a preliminary Differential Thermal Analysis (DTA) in order to give evidence for any chemical-physical coating modification in the temperature range of interest before performing accelerated aging tests. In the accelerated aging tests we assumed that the temperature dependence of the degradation processes could be described by Arrhenius behaviour and we hypothesized that a linear correlation occurs between optical parameter variation rate (specifically, Δαs/Δt) and degradation process rate. Starting from Δαs/Δt values evaluated at 650 and 690 °C, Arrhenius plot gave an activation energy of 325 kJ mol-1 for the degradation phenomenon, where the prediction on the coating degradation gave a solar absorptance decrease of only 1.65 % after 25 years at 550 °C. This very low αs decrease gave evidence for an excellent stability of our solar coating, also when employed at the maximum temperature (550 °C) of a solar field operating with molten salt as heat transfer fluid.
Micro-Feedback Training:Learning the art of effective feedback
Baseer, Najma; Mahboob, Usman; Degnan, James
2017-01-01
Multiple attributes are expected of postgraduate research supervisors. Provision of timely and effective face-to-face feedback is one such skill that carries enormous significance in supervisee’s professional development. Feedback allows the supervisees to improve upon their performances. Unfortunately, both supervisors and supervisees have contrasting approaches towards the ongoing feedback practices. This incongruence is attributed, in part, to a lack of structured pedagogic training among the medical professionals. A standardized schema is therefore required to acquire and harmonize this pedagogical skill. One such systemized way is a training method called microteaching. Microteaching has long been used to enhance and incorporate old and new undergraduate teaching skills, respectively. Here we propose a similar structured approach of micro-feedback to inculcate effective feedback skills among postgraduate research supervisors using feedback-based scenarios, simulated students, standardized checklists and audiovisual aids. Thus, micro-feedback exercise may prove to be quite promising in improving feedback practices of postgraduate research supervisors. PMID:29492091
Superconducting Microwave Multivibrator Produced by Coherent Feedback
NASA Astrophysics Data System (ADS)
Kerckhoff, Joseph; Lehnert, K. W.
2012-10-01
We investigate a nonlinear coherent feedback circuit constructed from preexisting superconducting microwave devices. The network exhibits emergent bistable and astable states, and we demonstrate its operation as a latch and the frequency locking of its oscillations. While the network is tedious to model by hand, our observations agree quite well with the semiclassical dynamical model produced by a new software package (N. Tezak , arXiv:1111.3081v1 [Phil. Trans. R. Soc. A (to be published)]) that systematically interpreted an idealized schematic of the system as a quantum optic feedback network.
Polarization-resolved time-delay signatures of chaos induced by FBG-feedback in VCSEL.
Zhong, Zhu-Qiang; Li, Song-Sui; Chan, Sze-Chun; Xia, Guang-Qiong; Wu, Zheng-Mao
2015-06-15
Polarization-resolved chaotic emission intensities from a vertical-cavity surface-emitting laser (VCSEL) subject to feedback from a fiber Bragg grating (FBG) are numerically investigated. Time-delay (TD) signatures of the feedback are examined through various means including self-correlations of intensity time-series of individual polarizations, cross-correlation of intensities time-series between both polarizations, and permutation entropies calculated for the individual polarizations. The results show that the TD signatures can be clearly suppressed by selecting suitable operation parameters such as the feedback strength, FBG bandwidth, and Bragg frequency. Also, in the operational parameter space, numerical maps of TD signatures and effective bandwidths are obtained, which show regions of chaotic signals with both wide bandwidths and weak TD signatures. Finally, by comparing with a VCSEL subject to feedback from a mirror, the VCSEL subject to feedback from the FBG generally shows better concealment of the TD signatures with similar, or even wider, bandwidths.
Oestergaard, Jeanett; Bjerrum, Flemming; Maagaard, Mathilde; Winkel, Per; Larsen, Christian Rifbjerg; Ringsted, Charlotte; Gluud, Christian; Grantcharov, Teodor; Ottesen, Bent; Soerensen, Jette Led
2012-02-28
Several studies have found a positive effect on the learning curve as well as the improvement of basic psychomotor skills in the operating room after virtual reality training. Despite this, the majority of surgical and gynecological departments encounter hurdles when implementing this form of training. This is mainly due to lack of knowledge concerning the time and human resources needed to train novice surgeons to an adequate level. The purpose of this trial is to investigate the impact of instructor feedback regarding time, repetitions and self-perception when training complex operational tasks on a virtual reality simulator. The study population consists of medical students on their 4th to 6th year without prior laparoscopic experience. The study is conducted in a skills laboratory at a centralized university hospital. Based on a sample size estimation 98 participants will be randomized to an intervention group or a control group. Both groups have to achieve a predefined proficiency level when conducting a laparoscopic salpingectomy using a surgical virtual reality simulator. The intervention group receives standardized instructor feedback of 10 to 12 min a maximum of three times. The control group receives no instructor feedback. Both groups receive the automated feedback generated by the virtual reality simulator. The study follows the CONSORT Statement for randomized trials. Main outcome measures are time and repetitions to reach the predefined proficiency level on the simulator. We include focus on potential sex differences, computer gaming experience and self-perception. The findings will contribute to a better understanding of optimal training methods in surgical education. NCT01497782.
Smart building temperature control using occupant feedback
NASA Astrophysics Data System (ADS)
Gupta, Santosh K.
feedback signals, we propose a distributed solution, which ensures that a consensus is attained among all occupants upon convergence, irrespective of their temperature preferences being in coherence or conflicting. Occupants are only assumed to be rational, in that they choose their own temperature set-points so as to minimize their individual energy cost plus discomfort. We use Alternating Direction Method of Multipliers ( ADMM) to solve our consensus problem. We further establish the convergence of the proposed algorithm to the optimal thermal set point values that minimize the sum of the energy cost and the aggregate discomfort of all occupants in a multi-zone building. For simulating our consensus algorithm we use realistic building parameters based on the Watervliet test facility. The simulation study based on real world building parameters establish the validity of our theoretical model and provide insights on the dynamics of the system with a mobile user population. In the third part we present a game-theoretic (auction) mechanism, that requires occupants to "purchase" their individualized comfort levels beyond what is provided by default by the building operator. The comfort pricing policy, derived as an extension of Vickrey-Clarke-Groves (VCG) pricing, ensures incentive-compatibility of the mechanism, i.e., an occupant acting in self-interest cannot benefit from declaring their comfort function untruthfully, irrespective of the choices made by other occupants. The declared (or estimated) occupant comfort ranges (functions) are then utilized by the building operator---along with the energy cost information---to set the environment controls to optimally balance the aggregate discomfort of the occupants and the energy cost of the building operator. We use realistic building model and parameters based on our test facility to demonstrate the convergence of the actual temperatures in different zones to the desired temperatures, and provide insight to the pricing
ERIC Educational Resources Information Center
Smith, David A.
2017-01-01
Feedback on assessed work is invaluable to student learning, but there is a limit to the amount of feedback an instructor may provide. Peer feedback increases the volume of feedback possible, but potentially reduces the quality of the feedback. This research proposes a model of collaborative peer feedback designed to increase quality of peer…
Ramani, Subha; Könings, Karen D; Mann, Karen V; Pisarski, Emily E; van der Vleuten, Cees P M
2018-03-06
To explore resident and faculty perspectives on what constitutes feedback culture, their perceptions of how institutional feedback culture (including politeness concepts) might influence the quality and impact of feedback, feedback seeking, receptivity, and readiness to engage in bidirectional feedback. Using a constructivist grounded theory approach, five focus group discussions with internal medicine residents, three focus group discussions with general medicine faculty, and eight individual interviews with subspecialist faculty were conducted at Brigham and Women's Hospital between April and December 2016. Discussions and interviews were audiotaped and transcribed verbatim; concurrent data collection and analysis were performed using the constant comparative approach. Analysis was considered through the lens of politeness theory and organizational culture. Twenty-nine residents and twenty-two general medicine faculty participated in focus group discussions, and eight subspecialty faculty participated in interviews. The institutional feedback culture was described by participants as: (1) a culture of politeness, in which language potentially damaging to residents' self-esteem was discouraged, and (2) a culture of excellence, in which the institution's outstanding reputation and pedigree of trainees inhibited constructive feedback. Three key themes situated within this broader cultural context were discovered: normalizing constructive feedback to promote a culture of growth, overcoming the mental block to feedback seeking, and hierarchical culture impeding bidirectional feedback. An institutional feedback culture of excellence and politeness may impede honest, meaningful feedback and may impact feedback seeking, receptivity, and bidirectional feedback exchanges. It is essential to understand the institutional feedback culture before it can be successfully changed.
Intra-operative feedback and dynamic compensation for image-guided robotic focal ultrasound surgery.
Chauhan, S; Amir, H; Chen, G; Hacker, A; Michel, M S; Koehrmann, K U
2008-11-01
This paper describes a non-invasive remote temperature measurement technique integrated with a biomechatronic surgery system devised in our laboratory and named FUSBOT (Focal Ultrasound Surgery RoBOT). FUSBOTs use High-Intensity Focused Ultrasound (HIFU) for ablation of cancers/tumors and targets accessible through various soft-tissue acoustic windows in the human body. The focused ultrasound beam parameters are chosen so that biologically significant temperature rises are achieved only within the focal volume. In this paper, FUSBOT(BS), a customized system for breast surgery, is taken as a representative example to demonstrate the implementation and the results of non-invasive feedback during ablation. An 8-axis PC-based controller controls various sub-sections of the system within a safe constrained work envelope. Temperature is a prime target parameter in ablative procedures, and it is of paramount importance that means should be devised for its measurement and control in order to design optimal dose protocols and judge the efficacy of FUS systems. A customized sensory interface is devised and integrated with FUSBOT(BS), and dedicated software algorithms are embedded for surgical planning based on real-time guidance and feedback. Variations in the physical parameters of the tissue interacting with the incident modality are used as surgical feedback. The use of real-time ultrasound imaging and data processed from various sensors to deduce lesion position and thermal feedback during surgery, as integrated with the robotic system for online surgical planning, is described. Dynamic registration algorithms are developed for compensation and re-registration of the robotic end-effector with respect to the target, and representative empirical outcomes for lesion tracking and online temperature estimation in various biological tissues are presented.
Indirect Identification of Linear Stochastic Systems with Known Feedback Dynamics
NASA Technical Reports Server (NTRS)
Huang, Jen-Kuang; Hsiao, Min-Hung; Cox, David E.
1996-01-01
An algorithm is presented for identifying a state-space model of linear stochastic systems operating under known feedback controller. In this algorithm, only the reference input and output of closed-loop data are required. No feedback signal needs to be recorded. The overall closed-loop system dynamics is first identified. Then a recursive formulation is derived to compute the open-loop plant dynamics from the identified closed-loop system dynamics and known feedback controller dynamics. The controller can be a dynamic or constant-gain full-state feedback controller. Numerical simulations and test data of a highly unstable large-gap magnetic suspension system are presented to demonstrate the feasibility of this indirect identification method.
A variable-gain output feedback control design methodology
NASA Technical Reports Server (NTRS)
Halyo, Nesim; Moerder, Daniel D.; Broussard, John R.; Taylor, Deborah B.
1989-01-01
A digital control system design technique is developed in which the control system gain matrix varies with the plant operating point parameters. The design technique is obtained by formulating the problem as an optimal stochastic output feedback control law with variable gains. This approach provides a control theory framework within which the operating range of a control law can be significantly extended. Furthermore, the approach avoids the major shortcomings of the conventional gain-scheduling techniques. The optimal variable gain output feedback control problem is solved by embedding the Multi-Configuration Control (MCC) problem, previously solved at ICS. An algorithm to compute the optimal variable gain output feedback control gain matrices is developed. The algorithm is a modified version of the MCC algorithm improved so as to handle the large dimensionality which arises particularly in variable-gain control problems. The design methodology developed is applied to a reconfigurable aircraft control problem. A variable-gain output feedback control problem was formulated to design a flight control law for an AFTI F-16 aircraft which can automatically reconfigure its control strategy to accommodate failures in the horizontal tail control surface. Simulations of the closed-loop reconfigurable system show that the approach produces a control design which can accommodate such failures with relative ease. The technique can be applied to many other problems including sensor failure accommodation, mode switching control laws and super agility.
The dynamics of climate-induced deglacial ice stream acceleration
NASA Astrophysics Data System (ADS)
Robel, A.; Tziperman, E.
2015-12-01
Geological observations indicate that ice streams were a significant contributor to ice flow in the Laurentide Ice Sheet during the Last Glacial Maximum. Conceptual and simple model studies have also argued that the gradual development of ice streams increases the sensitivity of large ice sheets to weak climate forcing. In this study, we use an idealized configuration of the Parallel Ice Sheet Model to explore the role of ice streams in rapid deglaciation. In a growing ice sheet, ice streams develop gradually as the bed warms and the margin expands outward onto the continental shelf. Then, a weak change in equilibrium line altitude commensurate with Milankovitch forcing results in a rapid deglacial response, as ice stream acceleration leads to enhanced calving and surface melting at low elevations. We explain the dynamical mechanism that drives this ice stream acceleration and its broader applicability as a feedback for enhancing ice sheet decay in response to climate forcing. We show how our idealized ice sheet simulations match geomorphological observations of deglacial ice stream variability and previous model-data analyses. We conclude with observations on the potential for interaction between ice streams and other feedback mechanisms within the earth system.
Stereoscopic, Force-Feedback Trainer For Telerobot Operators
NASA Technical Reports Server (NTRS)
Kim, Won S.; Schenker, Paul S.; Bejczy, Antal K.
1994-01-01
Computer-controlled simulator for training technicians to operate remote robots provides both visual and kinesthetic virtual reality. Used during initial stage of training; saves time and expense, increases operational safety, and prevents damage to robots by inexperienced operators. Computes virtual contact forces and torques of compliant robot in real time, providing operator with feel of forces experienced by manipulator as well as view in any of three modes: single view, two split views, or stereoscopic view. From keyboard, user specifies force-reflection gain and stiffness of manipulator hand for three translational and three rotational axes. System offers two simulated telerobotic tasks: insertion of peg in hole in three dimensions, and removal and insertion of drawer.
Land market feedbacks can undermine biodiversity conservation
Armsworth, Paul R.; Daily, Gretchen C.; Kareiva, Peter; Sanchirico, James N.
2006-01-01
The full or partial purchase of land has become a cornerstone of efforts to conserve biodiversity in countries with strong private property rights. Methods used to target areas for acquisition typically ignore land market dynamics. We show how conservation purchases affect land prices and generate feedbacks that can undermine conservation goals, either by displacing development toward biologically valuable areas or by accelerating its pace. The impact of these market feedbacks on the effectiveness of conservation depends on the ecological value of land outside nature reserves. Traditional, noneconomic approaches to site prioritization should perform adequately in places where land outside reserves supports little biodiversity. However, these approaches will perform poorly in locations where the countryside surrounding reserves is important for species’ persistence. Conservation investments can sometimes even be counterproductive, condemning more species than they save. Conservation is most likely to be compromised in the absence of accurate information on species distributions, which provides a strong argument for improving inventories of biodiversity. Accounting for land market dynamics in conservation planning is crucial for making smart investment decisions. PMID:16554375
Land market feedbacks can undermine biodiversity conservation.
Armsworth, Paul R; Daily, Gretchen C; Kareiva, Peter; Sanchirico, James N
2006-04-04
The full or partial purchase of land has become a cornerstone of efforts to conserve biodiversity in countries with strong private property rights. Methods used to target areas for acquisition typically ignore land market dynamics. We show how conservation purchases affect land prices and generate feedbacks that can undermine conservation goals, either by displacing development toward biologically valuable areas or by accelerating its pace. The impact of these market feedbacks on the effectiveness of conservation depends on the ecological value of land outside nature reserves. Traditional, noneconomic approaches to site prioritization should perform adequately in places where land outside reserves supports little biodiversity. However, these approaches will perform poorly in locations where the countryside surrounding reserves is important for species' persistence. Conservation investments can sometimes even be counterproductive, condemning more species than they save. Conservation is most likely to be compromised in the absence of accurate information on species distributions, which provides a strong argument for improving inventories of biodiversity. Accounting for land market dynamics in conservation planning is crucial for making smart investment decisions.
Initiation of combustion in the thermally choked ram accelerator
NASA Technical Reports Server (NTRS)
Bruckner, A. P.; Burnham, E. A.; Knowlen, C.; Hertzberg, A.; Bogdanoff, D. W.
1992-01-01
The methodology for initiating stable combustion in a ram accelerator operating in the thermally choked mode is presented in this paper. The ram accelerator is a high velocity ramjet-in-tube projectile launcher whose principle of operation is similar to that of an airbreathing ramjet. The subcaliber projectile travels supersonically through a stationary tube filled with a premixed combustible gas mixture. In the thermally choked propulsion mode subsonic combustion takes place behind the base of the projectile and leads to thermal choking, which stabilizes a normal shock system on the projectile, thus producing forward thrust. Projectiles with masses in the 45-90 g range have been accelerated to velocities up to 2650 m/sec in a 38 mm bore, 16 m long accelerator tube. Operation of the ram accelerator is started by injecting the projectile into the accelerator tube at velocities in the 700 - 1300 m/sec range by means of a conventional gas gun. A specially designed obturator, which seals the bore of the gun during this initial acceleration, enters the ram accelerator together with the projectile. The interaction of the obturator with the propellant gas ignites the gas mixture and establishes stable combustion behind the projectile.
Corticocortical feedback increases the spatial extent of normalization
Nassi, Jonathan J.; Gómez-Laberge, Camille; Kreiman, Gabriel; Born, Richard T.
2014-01-01
Normalization has been proposed as a canonical computation operating across different brain regions, sensory modalities, and species. It provides a good phenomenological description of non-linear response properties in primary visual cortex (V1), including the contrast response function and surround suppression. Despite its widespread application throughout the visual system, the underlying neural mechanisms remain largely unknown. We recently observed that corticocortical feedback contributes to surround suppression in V1, raising the possibility that feedback acts through normalization. To test this idea, we characterized area summation and contrast response properties in V1 with and without feedback from V2 and V3 in alert macaques and applied a standard normalization model to the data. Area summation properties were well explained by a form of divisive normalization, which computes the ratio between a neuron's driving input and the spatially integrated activity of a “normalization pool.” Feedback inactivation reduced surround suppression by shrinking the spatial extent of the normalization pool. This effect was independent of the gain modulation thought to mediate the influence of contrast on area summation, which remained intact during feedback inactivation. Contrast sensitivity within the receptive field center was also unaffected by feedback inactivation, providing further evidence that feedback participates in normalization independent of the circuit mechanisms involved in modulating contrast gain and saturation. These results suggest that corticocortical feedback contributes to surround suppression by increasing the visuotopic extent of normalization and, via this mechanism, feedback can play a critical role in contextual information processing. PMID:24910596
Investigation of control system of traction electric drive with feedbacks on load
NASA Astrophysics Data System (ADS)
Kuznetsov, N. K.; Iov, I. A.; Iov, A. A.
2018-03-01
In the article, by the example of a walking excavator, the results of a study of a control system of traction electric drive with a rigid and flexible feedback on the load are mentioned. Based on the analysis of known works, the calculation scheme has been chosen; the equations of motion of the electromechanical system have been obtained, taking into account the elasticity of the rope and feedbacks on the load in the elastic element. A simulation model of this system has been developed and mathematical modeling of the transient processes to evaluate the influence of feedback on the dynamic characteristics of the mechanism and its efficiency of work was carried out. It is shown that the use of rigid and flexible feedbacks makes it possible to reduce dynamic loads in the traction mechanism and to limit the elastic oscillation of the executive mechanism in transient operating modes in comparison with the standard control system; however, there is some decrease in productivity. It has been also established that the sign-variable of the loading of the electric drive, connected with the opening of the backlashes in the gearbox due to the action of feedbacks on the load in the elastic element, under certain conditions, can lead to undesirable phenomena in the operation of the drive and a decrease in the reliability of its operation.
Charged particle accelerator grating
Palmer, Robert B.
1986-01-01
A readily disposable and replaceable accelerator grating for a relativistic particle accelerator. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams into the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.
Charged particle accelerator grating
Palmer, R.B.
1985-09-09
A readily disposable and replaceable accelerator grating for a relativistic particle accelerator is described. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams onto the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.
Charged particle accelerator grating
Palmer, Robert B.
1986-09-02
A readily disposable and replaceable accelerator grating for a relativistic particle accelerator. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams into the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.
Temperature feedback control for long-term carrier-envelope phase locking
Chang, Zenghu [Manhattan, KS; Yun, Chenxia [Manhattan, KS; Chen, Shouyuan [Manhattan, KS; Wang, He [Manhattan, KS; Chini, Michael [Manhattan, KS
2012-07-24
A feedback control module for stabilizing a carrier-envelope phase of an output of a laser oscillator system comprises a first photodetector, a second photodetector, a phase stabilizer, an optical modulator, and a thermal control element. The first photodetector may generate a first feedback signal corresponding to a first portion of a laser beam from an oscillator. The second photodetector may generate a second feedback signal corresponding to a second portion of the laser beam filtered by a low-pass filter. The phase stabilizer may divide the frequency of the first feedback signal by a factor and generate an error signal corresponding to the difference between the frequency-divided first feedback signal and the second feedback signal. The optical modulator may modulate the laser beam within the oscillator corresponding to the error signal. The thermal control unit may change the temperature of the oscillator corresponding to a signal operable to control the optical modulator.
O'Connor, Paul
1998-08-11
A monolithic amplifier includes a stable, high resistance feedback circuit and a dynamic bias circuit. The dynamic bias circuit is formed with active elements matched to those in the amplifier and feedback circuit to compensate for variations in the operating and threshold voltages thereby maintaining a stable resistance in the feedback circuit.
Laterally Coupled Quantum-Dot Distributed-Feedback Lasers
NASA Technical Reports Server (NTRS)
Qui, Yueming; Gogna, Pawan; Muller, Richard; Maker, paul; Wilson, Daniel; Stintz, Andreas; Lester, Luke
2003-01-01
InAs quantum-dot lasers that feature distributed feedback and lateral evanescent- wave coupling have been demonstrated in operation at a wavelength of 1.3 m. These lasers are prototypes of optical-communication oscillators that are required to be capable of stable single-frequency, single-spatial-mode operation. A laser of this type (see figure) includes an active layer that comprises multiple stacks of InAs quantum dots embedded within InGaAs quantum wells. Distributed feedback is provided by gratings formed on both sides of a ridge by electron lithography and reactive-ion etching on the surfaces of an AlGaAs/GaAs waveguide. The lateral evanescent-wave coupling between the gratings and the wave propagating in the waveguide is strong enough to ensure operation at a single frequency, and the waveguide is thick enough to sustain a stable single spatial mode. In tests, the lasers were found to emit continuous-wave radiation at temperatures up to about 90 C. Side modes were found to be suppressed by more than 30 dB.
Generating clock signals for a cycle accurate, cycle reproducible FPGA based hardware accelerator
Asaad, Sameth W.; Kapur, Mohit
2016-01-05
A method, system and computer program product are disclosed for generating clock signals for a cycle accurate FPGA based hardware accelerator used to simulate operations of a device-under-test (DUT). In one embodiment, the DUT includes multiple device clocks generating multiple device clock signals at multiple frequencies and at a defined frequency ratio; and the FPG hardware accelerator includes multiple accelerator clocks generating multiple accelerator clock signals to operate the FPGA hardware accelerator to simulate the operations of the DUT. In one embodiment, operations of the DUT are mapped to the FPGA hardware accelerator, and the accelerator clock signals are generated at multiple frequencies and at the defined frequency ratio of the frequencies of the multiple device clocks, to maintain cycle accuracy between the DUT and the FPGA hardware accelerator. In an embodiment, the FPGA hardware accelerator may be used to control the frequencies of the multiple device clocks.
Plasma inverse transition acceleration
DOE Office of Scientific and Technical Information (OSTI.GOV)
Xie, Ming
It can be proved fundamentally from the reciprocity theorem with which the electromagnetism is endowed that corresponding to each spontaneous process of radiation by a charged particle there is an inverse process which defines a unique acceleration mechanism, from Cherenkov radiation to inverse Cherenkov acceleration (ICA) [1], from Smith-Purcell radiation to inverse Smith-Purcell acceleration (ISPA) [2], and from undulator radiation to inverse undulator acceleration (IUA) [3]. There is no exception. Yet, for nearly 30 years after each of the aforementioned inverse processes has been clarified for laser acceleration, inverse transition acceleration (ITA), despite speculation [4], has remained the least understood,more » and above all, no practical implementation of ITA has been found, until now. Unlike all its counterparts in which phase synchronism is established one way or the other such that a particle can continuously gain energy from an acceleration wave, the ITA to be discussed here, termed plasma inverse transition acceleration (PITA), operates under fundamentally different principle. As a result, the discovery of PITA has been delayed for decades, waiting for a conceptual breakthrough in accelerator physics: the principle of alternating gradient acceleration [5, 6, 7, 8, 9, 10]. In fact, PITA was invented [7, 8] as one of several realizations of the new principle.« less
In Situ Observations of Snow Metamorphosis Acceleration Induced by Dust and Black Carbon
NASA Astrophysics Data System (ADS)
Schneider, A. M.; Flanner, M.
2017-12-01
Previous studies demonstrate the dependence of shortwave infrared (SWIR) reflectance on snow specific surface area (SSA) and others examine the direct darkening effect dust and black carbon (BC) deposition has on snow and ice-covered surfaces. The extent to which these light absorbing aerosols (LAAs) accelerate snow metamorphosis, however, is challenging to assess in situ as measurement techniques easily disturb snowpack. Here, we use two Near-Infrared Emitting Reflectance Domes (NERDs) to measure 1300 and 1550nm bidirectional reflectance factors (BRFs) of natural snow and experimental plots with added dust and BC. We obtain NERD measurements and subsequently collect and transport snow samples to the nearby U.S. Army Corps of Engineers' Cold Regions Research and Engineering Lab for micro computed tomography (micro-CT) analysis. Snow 1300 (1550) nm BRFs evolve from 0.6 (0.15) in fresh snow to 0.2 (0.03) after metamorphosis. Hourly-scale time evolving snow surface BRFs and SSA estimates from micro-CT reveal more rapid SWIR darkening and snow metamorphosis in contaminated versus natural plots. Cloudiness and high wind speeds can completely obscure these results if LAAs mobilize before absorbing enough radiant energy. These findings verify experimentally that dust and BC deposition can accelerate snow metamorphosis and enhance snow albedo feedback in sunny, calm weather conditions. Although quantifying the enhancement of snow albedo feedback induced by LAAs requires further surface temperature, solar irradiance, and impurity concentration measurements, this study provides experimental verification of positive feedback occurring where dust and BC accelerate snow metamorphosis.
High field gradient particle accelerator
Nation, J.A.; Greenwald, S.
1989-05-30
A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications is disclosed. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle. 10 figs.
High field gradient particle accelerator
Nation, John A.; Greenwald, Shlomo
1989-01-01
A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle.
New MHD feedback control schemes using the MARTe framework in RFX-mod
NASA Astrophysics Data System (ADS)
Piron, Chiara; Manduchi, Gabriele; Marrelli, Lionello; Piovesan, Paolo; Zanca, Paolo
2013-10-01
Real-time feedback control of MHD instabilities is a topic of major interest in magnetic thermonuclear fusion, since it allows to optimize a device performance even beyond its stability bounds. The stability properties of different magnetic configurations are important test benches for real-time control systems. RFX-mod, a Reversed Field Pinch experiment that can also operate as a tokamak, is a well suited device to investigate this topic. It is equipped with a sophisticated magnetic feedback system that controls MHD instabilities and error fields by means of 192 active coils and a corresponding grid of sensors. In addition, the RFX-mod control system has recently gained new potentialities thanks to the introduction of the MARTe framework and of a new CPU architecture. These capabilities allow to study new feedback algorithms relevant to both RFP and tokamak operation and to contribute to the debate on the optimal feedback strategy. This work focuses on the design of new feedback schemes. For this purpose new magnetic sensors have been explored, together with new algorithms that refine the de-aliasing computation of the radial sideband harmonics. The comparison of different sensor and feedback strategy performance is described in both RFP and tokamak experiments.
Portable Dextrous Force Feedback Master for robot telemanipulation (PDMFF)
NASA Technical Reports Server (NTRS)
Burdea, Grigore C.; Speeter, Thomas H.
1989-01-01
A major drawback of open loop masters is a lack of force feedback, limiting their ability to perform complex tasks such as assembly and repair. Researchers present a simple dextrous force feedback master for computer assisted telemanipulation. The device is compact, portable and can be held in the operator hand, without the need for a special joystick or console. The system is capable of both position feed forward and force feedback, using electronic position sensors and a pneumatic micro-actuator. The level of forces exercised by the pneumatic actuator is such that near rigidity may be attained. Experimental results showing good system linearity and small time lag are given.
Apparatus for providing sensory substitution of force feedback
NASA Technical Reports Server (NTRS)
Massimino, Michael J. (Inventor); Sheridan, Thomas B. (Inventor)
1995-01-01
A feedback apparatus for an operator to control an effector that is remote from the operator to interact with a remote environment has a local input device to be manipulated by the operator. Sensors in the effector's environment are capable of sensing the amplitude of forces arising between the effector and its environment, the direction of application of such forces, or both amplitude and direction. A feedback signal corresponding to such a component of the force, is generated and transmitted to the environment of the operator. The signal is transduced into an auditory sensory substitution signal to which the operator is sensitive. Sound production apparatus present the auditory signal to the operator. The full range of the force amplitude may be represented by a single, audio speaker. Auditory display elements may be stereo headphones or free standing audio speakers, numbering from one to many more than two. The location of the application of the force may also be specified by the location of audio speakers that generate signals corresponding to specific forces. Alternatively, the location may be specified by the frequency of an audio signal, or by the apparent location of an audio signal, as simulated by a combination of signals originating at different locations.
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)
O`Connor, P.
1998-08-11
A monolithic amplifier includes a stable, high resistance feedback circuit and a dynamic bias circuit. The dynamic bias circuit is formed with active elements matched to those in the amplifier and feedback circuit to compensate for variations in the operating and threshold voltages thereby maintaining a stable resistance in the feedback circuit. 11 figs.
Slow Orbit Feedback at the ALS Using Matlab
DOE Office of Scientific and Technical Information (OSTI.GOV)
Portmann, G.
1999-03-25
The third generation Advanced Light Source (ALS) produces extremely bright and finely focused photon beams using undulatory, wigglers, and bend magnets. In order to position the photon beams accurately, a slow global orbit feedback system has been developed. The dominant causes of orbit motion at the ALS are temperature variation and insertion device motion. This type of motion can be removed using slow global orbit feedback with a data rate of a few Hertz. The remaining orbit motion in the ALS is only 1-3 micron rms. Slow orbit feedback does not require high computational throughput. At the ALS, the globalmore » orbit feedback algorithm, based on the singular valued decomposition method, is coded in MATLAB and runs on a control room workstation. Using the MATLAB environment to develop, test, and run the storage ring control algorithms has proven to be a fast and efficient way to operate the ALS.« less
Durkin, Anne E; Feinn, Richard S
The aim of the study was to examine self-efficacy among traditional and accelerated nursing students with regard to interprofessional learning. The World Health Organization and other organizations recognize the need for interprofessional education to prepare health care providers for collaborative practice. Graduates of baccalaureate nursing programs require competence in interprofessional collaboration and communication. Traditional (n = 239) and accelerated (n = 114) nursing students' self-efficacy was measured utilizing Mann et al.'s Self-Efficacy for Interprofessional Experiential Learning Scale. Accelerated students averaged significantly higher than traditional students on the interprofessional team evaluation and feedback subscale (p = .006) and overall self-efficacy (p = .041). Awareness of possible differences between traditional and accelerated nursing students with regard to self-efficacy may help faculty develop effective interprofessional learning experiences for students in each cohort. Although results cannot be generalized, findings from this study provide evidence to guide the selection of learning strategies.
Accelerated deflation promotes homogeneous airspace liquid distribution in the edematous lung
Wu, You; Nguyen, Tam L.
2017-01-01
Edematous lungs contain regions with heterogeneous alveolar flooding. Liquid is trapped in flooded alveoli by a pressure barrier—higher liquid pressure at the border than in the center of flooded alveoli—that is proportional to surface tension, T. Stress is concentrated between aerated and flooded alveoli, to a degree proportional to T. Mechanical ventilation, by cyclically increasing T, injuriously exacerbates stress concentrations. Overcoming the pressure barrier to redistribute liquid more homogeneously between alveoli should reduce stress concentration prevalence and ventilation injury. In isolated rat lungs, we test whether accelerated deflation can overcome the pressure barrier and catapult liquid out of flooded alveoli. We generate a local edema model with normal T by microinfusing liquid into surface alveoli. We generate a global edema model with high T by establishing hydrostatic edema, which does not alter T, and then gently ventilating the edematous lungs, which increases T at 15 cmH2O transpulmonary pressure by 52%. Thus ventilation of globally edematous lungs increases T, which should increase stress concentrations and, with positive feedback, cause escalating ventilation injury. In the local model, when the pressure barrier is moderate, accelerated deflation causes liquid to escape from flooded alveoli and redistribute more equitably. Flooding heterogeneity tends to decrease. In the global model, accelerated deflation causes liquid escape, but—because of elevated T—the liquid jumps to nearby, aerated alveoli. Flooding heterogeneity is unaltered. In pulmonary edema with normal T, early ventilation with accelerated deflation might reduce the positive feedback mechanism through which ventilation injury increases over time. NEW & NOTEWORTHY We introduce, in the isolated rat lung, a new model of pulmonary edema with elevated surface tension. We first generate hydrostatic edema and then ventilate gently to increase surface tension. We investigate
Feedback from incident reporting: information and action to improve patient safety.
Benn, J; Koutantji, M; Wallace, L; Spurgeon, P; Rejman, M; Healey, A; Vincent, C
2009-02-01
Effective feedback from incident reporting systems in healthcare is essential if organisations are to learn from failures in the delivery of care. Despite the wide-scale development and implementation of incident reporting in healthcare, studies in the UK suggest that information concerning system vulnerabilities could be better applied to improve operational safety within organisations. In this article, the findings and implications of research to identify forms of effective feedback from incident reporting are discussed, to promote best practices in this area. The research comprised a mixed methods review to investigate mechanisms of effective feedback for healthcare, drawing upon experience within established reporting programmes in high-risk industry and transport domains. Systematic searches of published literature were undertaken, and 23 case studies describing incident reporting programmes with feedback were identified for analysis from the international healthcare literature. Semistructured interviews were undertaken with 19 subject matter experts across a range of domains, including: civil aviation, maritime, energy, rail, offshore production and healthcare. In analysis, qualitative information from several sources was synthesised into practical requirements for developing effective feedback in healthcare. Both action and information feedback mechanisms were identified, serving safety awareness, improvement and motivational functions. The provision of actionable feedback that visibly improved systems was highlighted as important in promoting future reporting. Fifteen requirements for the design of effective feedback systems were identified, concerning: the role of leadership, the credibility and content of information, effective dissemination channels, the capacity for rapid action and the need for feedback at all levels of the organisation, among others. Above all, the safety-feedback cycle must be closed by ensuring that reporting, analysis and
Regulation of landslide motion by dilatancy and pore pressure feedback
Iverson, R.M.
2005-01-01
A new mathematical model clarifies how diverse styles and rates of landslide motion can result from regulation of Coulomb friction by dilation or contraction of water-saturated basal shear zones. Normalization of the model equations shows that feedback due to coupling between landslide motion, shear zone volume change, and pore pressure change depends on a single dimensionless parameter ??, which, in turn, depends on the dilatancy angle ?? and the intrinsic timescales for pore pressure generation and dissipation. If shear zone soil contracts during slope failure, then ?? 0, and negative feedback permits slow, steady landslide motion to occur while positive pore pressure is supplied by rain infiltration. Steady state slip velocities v0 obey v0 = -(K/??) p*e, where K is the hydraulic conductivity and p*e is the normalized (dimensionless) negative pore pressure generated by dilation. If rain infiltration and attendant pore pressure growth continue unabated, however, their influence ultimately overwhelms the stabilizing influence of negative p*e. Then, unbounded landslide acceleration occurs, accentuated by an instability that develops if ?? diminishes as landslide motion proceeds. Nonetheless, numerical solutions of the model equations show that slow, nearly steady motion of a clay-rich landslide may persist for many months as a result of negative pore pressure feedback that regulates basal Coulomb friction. Similarly stabilized motion is less likely to occur in sand-rich landslides that are characterized by weaker negative feedback.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Spentzouris, P.; /Fermilab; Cary, J.
PASS organization for software development and applications accounts for the natural domain areas (beam dynamics, electromagnetics, and advanced acceleration), and all areas depend on the enabling technologies activities, such as solvers and component technology, to deliver the desired performance and integrated simulation environment. The ComPASS applications focus on computationally challenging problems important for design or performance optimization to all major HEP, NP, and BES accelerator facilities. With the cost and complexity of particle accelerators rising, the use of computation to optimize their designs and find improved operating regimes becomes essential, potentially leading to significant cost savings with modest investment.« less
Perceived Insider Status and Feedback Reactions: A Dual Path of Feedback Motivation Attribution.
Chen, Xiao; Liao, JianQiao; Wu, Weijiong; Zhang, Wei
2017-01-01
Many studies have evaluated how the characteristics of feedback receiver, feedback deliverer and feedback information influence psychological feedback reactions of the feedback receiver while largely neglecting that feedback intervention is a kind of social interaction process. To address this issue, this study proposes that employees' perceived insider status (PIS), as a kind of employee-organization relationship, could also influence employees' reactions to supervisory feedback. In particular, this study investigates the influence of PIS focusing on affective and cognitive feedback reactions, namely feedback satisfaction and feedback utility. Surveys were conducted in a machinery manufacturing company in the Guangdong province of China. Samples were collected from 192 employees. Data analysis demonstrated that PIS and feedback utility possessed a U-shaped relationship, whereas PIS and feedback satisfaction exhibited positively linear relationships. The analysis identified two kinds of mediating mechanisms related to feedback satisfaction and feedback utility. Internal feedback motivation attribution partially mediated the relationship between PIS and feedback satisfaction but failed to do the same with respect to the relationship between PIS and feedback utility. In contrast, external feedback motivation attribution partially mediated the relationship between PIS and feedback utility while failing to mediate the relationship between PIS and feedback satisfaction. Theoretical contributions and practical implications of the findings are discussed at the end of the paper.
2012-01-01
Abstract Background Several studies have found a positive effect on the learning curve as well as the improvement of basic psychomotor skills in the operating room after virtual reality training. Despite this, the majority of surgical and gynecological departments encounter hurdles when implementing this form of training. This is mainly due to lack of knowledge concerning the time and human resources needed to train novice surgeons to an adequate level. The purpose of this trial is to investigate the impact of instructor feedback regarding time, repetitions and self-perception when training complex operational tasks on a virtual reality simulator. Methods/Design The study population consists of medical students on their 4th to 6th year without prior laparoscopic experience. The study is conducted in a skills laboratory at a centralized university hospital. Based on a sample size estimation 98 participants will be randomized to an intervention group or a control group. Both groups have to achieve a predefined proficiency level when conducting a laparoscopic salpingectomy using a surgical virtual reality simulator. The intervention group receives standardized instructor feedback of 10 to 12 min a maximum of three times. The control group receives no instructor feedback. Both groups receive the automated feedback generated by the virtual reality simulator. The study follows the CONSORT Statement for randomized trials. Main outcome measures are time and repetitions to reach the predefined proficiency level on the simulator. We include focus on potential sex differences, computer gaming experience and self-perception. Discussion The findings will contribute to a better understanding of optimal training methods in surgical education. Trial Registration NCT01497782 PMID:22373062
An integrated optical sensor for GMAW feedback control
DOE Office of Scientific and Technical Information (OSTI.GOV)
Taylor, P.L.; Watkins, A.D.; Larsen, E.D.
1992-08-01
The integrated optical sensor (IOS) is a multifunction feedback control sensor for arc welding, that is computer automated and independent of significant operator interaction. It is based on three major ``off-the-shelf`` components: a charged coupled device (CCD) camera, a diode laser, and a processing computer. The sensor head is compact and lightweight to avoid interference with weld head mobility, hardened to survive the harsh operating environment, and free of specialized cooling and power requirements. The sensor is positioned behind the GMAW torch and measures weld pool position and width, standoff distance, and postweld centerline cooling rate. Weld pool position andmore » width are used in a feedback loop, by the weld controller, to track the weld pool relative to the weld joint, thus allowing compensation for such phenomena as arc blow. Sensor stand off distance is used in a feedback loop to control the contact tip to base metal distance during the welding process. Cooling rate information is used to infer the final metallurgical state of the weld bead and heat affected zone, thereby providing a means of controlling post weld mechanical properties.« less
An integrated optical sensor for GMAW feedback control
DOE Office of Scientific and Technical Information (OSTI.GOV)
Taylor, P.L.; Watkins, A.D.; Larsen, E.D.
1992-01-01
The integrated optical sensor (IOS) is a multifunction feedback control sensor for arc welding, that is computer automated and independent of significant operator interaction. It is based on three major off-the-shelf'' components: a charged coupled device (CCD) camera, a diode laser, and a processing computer. The sensor head is compact and lightweight to avoid interference with weld head mobility, hardened to survive the harsh operating environment, and free of specialized cooling and power requirements. The sensor is positioned behind the GMAW torch and measures weld pool position and width, standoff distance, and postweld centerline cooling rate. Weld pool position andmore » width are used in a feedback loop, by the weld controller, to track the weld pool relative to the weld joint, thus allowing compensation for such phenomena as arc blow. Sensor stand off distance is used in a feedback loop to control the contact tip to base metal distance during the welding process. Cooling rate information is used to infer the final metallurgical state of the weld bead and heat affected zone, thereby providing a means of controlling post weld mechanical properties.« less
A numerical algorithm for optimal feedback gains in high dimensional LQR problems
NASA Technical Reports Server (NTRS)
Banks, H. T.; Ito, K.
1986-01-01
A hybrid method for computing the feedback gains in linear quadratic regulator problems is proposed. The method, which combines the use of a Chandrasekhar type system with an iteration of the Newton-Kleinman form with variable acceleration parameter Smith schemes, is formulated so as to efficiently compute directly the feedback gains rather than solutions of an associated Riccati equation. The hybrid method is particularly appropriate when used with large dimensional systems such as those arising in approximating infinite dimensional (distributed parameter) control systems (e.g., those governed by delay-differential and partial differential equations). Computational advantage of the proposed algorithm over the standard eigenvector (Potter, Laub-Schur) based techniques are discussed and numerical evidence of the efficacy of our ideas presented.
Analytically tractable climate-carbon cycle feedbacks under 21st century anthropogenic forcing
NASA Astrophysics Data System (ADS)
Lade, Steven J.; Donges, Jonathan F.; Fetzer, Ingo; Anderies, John M.; Beer, Christian; Cornell, Sarah E.; Gasser, Thomas; Norberg, Jon; Richardson, Katherine; Rockström, Johan; Steffen, Will
2018-05-01
Changes to climate-carbon cycle feedbacks may significantly affect the Earth system's response to greenhouse gas emissions. These feedbacks are usually analysed from numerical output of complex and arguably opaque Earth system models. Here, we construct a stylised global climate-carbon cycle model, test its output against comprehensive Earth system models, and investigate the strengths of its climate-carbon cycle feedbacks analytically. The analytical expressions we obtain aid understanding of carbon cycle feedbacks and the operation of the carbon cycle. Specific results include that different feedback formalisms measure fundamentally the same climate-carbon cycle processes; temperature dependence of the solubility pump, biological pump, and CO2 solubility all contribute approximately equally to the ocean climate-carbon feedback; and concentration-carbon feedbacks may be more sensitive to future climate change than climate-carbon feedbacks. Simple models such as that developed here also provide workbenches
for simple but mechanistically based explorations of Earth system processes, such as interactions and feedbacks between the planetary boundaries, that are currently too uncertain to be included in comprehensive Earth system models.
Ultrafast Outflows: Galaxy-scale Active Galactic Nucleus Feedback
NASA Astrophysics Data System (ADS)
Wagner, A. Y.; Umemura, M.; Bicknell, G. V.
2013-01-01
We show, using global three-dimensional grid-based hydrodynamical simulations, that ultrafast outflows (UFOs) from active galactic nuclei (AGNs) result in considerable feedback of energy and momentum into the interstellar medium (ISM) of the host galaxy. The AGN wind interacts strongly with the inhomogeneous, two-phase ISM consisting of dense clouds embedded in a tenuous, hot, hydrostatic medium. The outflow floods through the intercloud channels, sweeps up the hot ISM, and ablates and disperses the dense clouds. The momentum of the UFO is primarily transferred to the dense clouds via the ram pressure in the channel flow, and the wind-blown bubble evolves in the energy-driven regime. Any dependence on UFO opening angle disappears after the first interaction with obstructing clouds. On kpc scales, therefore, feedback by UFOs operates similarly to feedback by relativistic AGN jets. Negative feedback is significantly stronger if clouds are distributed spherically rather than in a disk. In the latter case, the turbulent backflow of the wind drives mass inflow toward the central black hole. Considering the common occurrence of UFOs in AGNs, they are likely to be important in the cosmological feedback cycles of galaxy formation.
ULTRAFAST OUTFLOWS: GALAXY-SCALE ACTIVE GALACTIC NUCLEUS FEEDBACK
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wagner, A. Y.; Umemura, M.; Bicknell, G. V., E-mail: ayw@ccs.tsukuba.ac.jp
We show, using global three-dimensional grid-based hydrodynamical simulations, that ultrafast outflows (UFOs) from active galactic nuclei (AGNs) result in considerable feedback of energy and momentum into the interstellar medium (ISM) of the host galaxy. The AGN wind interacts strongly with the inhomogeneous, two-phase ISM consisting of dense clouds embedded in a tenuous, hot, hydrostatic medium. The outflow floods through the intercloud channels, sweeps up the hot ISM, and ablates and disperses the dense clouds. The momentum of the UFO is primarily transferred to the dense clouds via the ram pressure in the channel flow, and the wind-blown bubble evolves inmore » the energy-driven regime. Any dependence on UFO opening angle disappears after the first interaction with obstructing clouds. On kpc scales, therefore, feedback by UFOs operates similarly to feedback by relativistic AGN jets. Negative feedback is significantly stronger if clouds are distributed spherically rather than in a disk. In the latter case, the turbulent backflow of the wind drives mass inflow toward the central black hole. Considering the common occurrence of UFOs in AGNs, they are likely to be important in the cosmological feedback cycles of galaxy formation.« less
Perceived Insider Status and Feedback Reactions: A Dual Path of Feedback Motivation Attribution
Chen, Xiao; Liao, JianQiao; Wu, Weijiong; Zhang, Wei
2017-01-01
Many studies have evaluated how the characteristics of feedback receiver, feedback deliverer and feedback information influence psychological feedback reactions of the feedback receiver while largely neglecting that feedback intervention is a kind of social interaction process. To address this issue, this study proposes that employees’ perceived insider status (PIS), as a kind of employee-organization relationship, could also influence employees’ reactions to supervisory feedback. In particular, this study investigates the influence of PIS focusing on affective and cognitive feedback reactions, namely feedback satisfaction and feedback utility. Surveys were conducted in a machinery manufacturing company in the Guangdong province of China. Samples were collected from 192 employees. Data analysis demonstrated that PIS and feedback utility possessed a U-shaped relationship, whereas PIS and feedback satisfaction exhibited positively linear relationships. The analysis identified two kinds of mediating mechanisms related to feedback satisfaction and feedback utility. Internal feedback motivation attribution partially mediated the relationship between PIS and feedback satisfaction but failed to do the same with respect to the relationship between PIS and feedback utility. In contrast, external feedback motivation attribution partially mediated the relationship between PIS and feedback utility while failing to mediate the relationship between PIS and feedback satisfaction. Theoretical contributions and practical implications of the findings are discussed at the end of the paper. PMID:28507527
Redundant operation of counter modules
NASA Technical Reports Server (NTRS)
Nagano, S. (Inventor)
1980-01-01
A technique for the redundant operation of counter modules is described. Redundant operation is maintained by detecting the zero state of each counter and clearing the other to that state, thus periodically resynchronizing the counters, and obtaining an output from both counters through AC coupled diode-OR gates. Redundant operation of counter flip flops is maintained in a similar manner, and synchronous operation of redundant squarewave clock generators of the feedback type is effected by connecting together the feedback inputs of the squarewave generators through a coupling resistor, and obtaining an output from both generators through AC coupled diode-OR gates.
Advances in high gradient normal conducting accelerator structures
Simakov, Evgenya Ivanovna; Dolgashev, Valery A.; Tantawi, Sami G.
2018-03-09
Here, this paper reviews the current state-of-the-art in understanding the phenomena of ultra-high vacuum radio-frequency (rf) breakdown in accelerating structures and the efforts to improve stable operation of the structures at accelerating gradients above 100 MV/m. Numerous studies have been conducted recently with the goal of understanding the dependence of the achievable accelerating gradients and breakdown rates on the frequency of operations, the geometry of the structure, material and method of fabrication, and operational temperature. Tests have been conducted with single standing wave accelerator cells as well as with the multi-cell traveling wave structures. Notable theoretical effort was directed atmore » understanding the physical mechanisms of the rf breakdown and its statistical behavior. Finally, the achievements presented in this paper are the result of the large continuous self-sustaining collaboration of multiple research institutions in the United States and worldwide.« less
Advances in high gradient normal conducting accelerator structures
DOE Office of Scientific and Technical Information (OSTI.GOV)
Simakov, Evgenya Ivanovna; Dolgashev, Valery A.; Tantawi, Sami G.
Here, this paper reviews the current state-of-the-art in understanding the phenomena of ultra-high vacuum radio-frequency (rf) breakdown in accelerating structures and the efforts to improve stable operation of the structures at accelerating gradients above 100 MV/m. Numerous studies have been conducted recently with the goal of understanding the dependence of the achievable accelerating gradients and breakdown rates on the frequency of operations, the geometry of the structure, material and method of fabrication, and operational temperature. Tests have been conducted with single standing wave accelerator cells as well as with the multi-cell traveling wave structures. Notable theoretical effort was directed atmore » understanding the physical mechanisms of the rf breakdown and its statistical behavior. Finally, the achievements presented in this paper are the result of the large continuous self-sustaining collaboration of multiple research institutions in the United States and worldwide.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
De Doncker, Rik W. A. A.
The direct (d) and quadrature (q) components of flux, as sensed by flux sensors or determined from voltage and current measurements in a direct field orientation scheme, are processed rapidly and accurately to provide flux amplitude and angular position values for use by the vector rotator of a universal field-oriented (UFO) controller. Flux amplitude (linear or squared) is provided as feedback to tune the UFO controller for operation in direct and indirect field orientation modes and enables smooth transitions from one mode to the other.
Multi-beam linear accelerator EVT
NASA Astrophysics Data System (ADS)
Teryaev, Vladimir E.; Kazakov, Sergey Yu.; Hirshfield, Jay L.
2016-09-01
A novel electron multi-beam accelerator is presented. The accelerator, short-named EVT (Electron Voltage Transformer) belongs to the class of two-beam accelerators. It combines an RF generator and essentially an accelerator within the same vacuum envelope. Drive beam-lets and an accelerated beam are modulated in RF modulators and then bunches pass into an accelerating structure, comprising uncoupled with each other and inductive tuned cavities, where the energy transfer from the drive beams to the accelerated beam occurs. A phasing of bunches is solved by choice correspond distances between gaps of the adjacent cavities. Preliminary results of numerical simulations and the initial specification of EVT operating in S-band, with a 60 kV gun and generating a 2.7 A, 1.1 MV beam at its output is presented. A relatively high efficiency of 67% and high design average power suggest that EVT can find its use in industrial applications.
Multi-beam linear accelerator EVT
Teryaev, Vladimir E.; Kazakov, Sergey Yu.; Hirshfield, Jay L.
2016-03-29
A novel electron multi-beam accelerator is presented. The accelerator, short-named EVT (Electron Voltage Transformer) belongs to the class of two-beam accelerators. It combines an RF generator and essentially an accelerator within the same vacuum envelope. Drive beam-lets and an accelerated beam are modulated in RF modulators and then bunches pass into an accelerating structure, comprising uncoupled with each other and inductive tuned cavities, where the energy transfer from the drive beams to the accelerated beam occurs. A phasing of bunches is solved by choice correspond distances between gaps of the adjacent cavities. Preliminary results of numerical simulations and the initialmore » specification of EVT operating in S-band, with a 60 kV gun and generating a 2.7 A, 1.1 MV beam at its output is presented. Furthermore, a relatively high efficiency of 67% and high design average power suggest that EVT can find its use in industrial applications.« less
Dynamic Mesoscale Land-Atmosphere Feedbacks in Fragmented Forests in Amazonia
NASA Astrophysics Data System (ADS)
Rastogi, D.; Baidya Roy, S.
2011-12-01
This paper investigates land-atmosphere feedbacks in disturbed rainforests of Amazonia. Deforestation along the rapidly expanding highways and road network has created the unique fishbone land cover pattern in Rondonia, a state in southwestern Amazonia. Numerical experiments and observations show that sharp gradients in land cover due to the fishbone heterogeneity triggers mesoscale circulations. These circulations significantly change the spatial pattern of local hydrometeorology, especially convection, clouds and precipitation. The primary research question now is can these changes in local hydrometeorology affect vegetation growth in the clearings. If so, that would be a clear indication that land-atmosphere feedbacks can affect vegetation recovery in fragmented forests. A computationally-efficient modeling tool consisting of a mesoscale atmospheric model dynamically coupled with a plant growth model has been specifically developed to identify the atmospheric feedback pathways. Preliminary experiments focus on the seasonal-scale feedbacks during the dry season. Results show that temperature, incoming shortwave and precipitation are the three primary drivers through which the feedbacks operate. Increasing temperature increases respiratory losses generating a positive feedback. Increased cloud cover reduces incoming PAR and photosynthesis, resulting in a positive feedback. Increased precipitation reduces water stress and promotes growth resulting in a negative feedback. The net effect is a combination of these 3 feedback loops. These findings can significantly improve our understanding of ecosystem resiliency in disturbed tropical forests.
Offset quadrature communications with decision-feedback carrier synchronization
NASA Technical Reports Server (NTRS)
Simon, M. K.; Smith, J. G.
1974-01-01
In order to accommodate a quadrature amplitude-shift-keyed (QASK) signal, Simon and Smith (1974) have modified the decision-feedback loop which tracks a quadrature phase-shift-keyed (QPSK). In the investigation reported approaches are considered to modify the loops in such a way that offset QASK signals can be tracked, giving attention to the special case of an offset QPSK. The development of the stochastic integro-differential equation of operation for a decision-feedback offset QASK loop is discussed along with the probability density function of the phase error process.
Self-adaptive relevance feedback based on multilevel image content analysis
NASA Astrophysics Data System (ADS)
Gao, Yongying; Zhang, Yujin; Fu, Yu
2001-01-01
In current content-based image retrieval systems, it is generally accepted that obtaining high-level image features is a key to improve the querying. Among the related techniques, relevance feedback has become a hot research aspect because it combines the information from the user to refine the querying results. In practice, many methods have been proposed to achieve the goal of relevance feedback. In this paper, a new scheme for relevance feedback is proposed. Unlike previous methods for relevance feedback, our scheme provides a self-adaptive operation. First, based on multi- level image content analysis, the relevant images from the user could be automatically analyzed in different levels and the querying could be modified in terms of different analysis results. Secondly, to make it more convenient to the user, the procedure of relevance feedback could be led with memory or without memory. To test the performance of the proposed method, a practical semantic-based image retrieval system has been established, and the querying results gained by our self-adaptive relevance feedback are given.
Self-adaptive relevance feedback based on multilevel image content analysis
NASA Astrophysics Data System (ADS)
Gao, Yongying; Zhang, Yujin; Fu, Yu
2000-12-01
In current content-based image retrieval systems, it is generally accepted that obtaining high-level image features is a key to improve the querying. Among the related techniques, relevance feedback has become a hot research aspect because it combines the information from the user to refine the querying results. In practice, many methods have been proposed to achieve the goal of relevance feedback. In this paper, a new scheme for relevance feedback is proposed. Unlike previous methods for relevance feedback, our scheme provides a self-adaptive operation. First, based on multi- level image content analysis, the relevant images from the user could be automatically analyzed in different levels and the querying could be modified in terms of different analysis results. Secondly, to make it more convenient to the user, the procedure of relevance feedback could be led with memory or without memory. To test the performance of the proposed method, a practical semantic-based image retrieval system has been established, and the querying results gained by our self-adaptive relevance feedback are given.
NASA Technical Reports Server (NTRS)
Gopher, D.; Wickens, C. D.
1975-01-01
A one dimensional compensatory tracking task and a digit processing reaction time task were combined in a three phase experiment designed to investigate tracking performance in time sharing. Adaptive techniques, elaborate feedback devices, and on line standardization procedures were used to adjust task difficulty to the ability of each individual subject and manipulate time sharing demands. Feedback control analysis techniques were employed in the description of tracking performance. The experimental results show that when the dynamics of a system are constrained, in such a manner that man machine system stability is no longer a major concern of the operator, he tends to adopt a first order control describing function, even with tracking systems of higher order. Attention diversion to a concurrent task leads to an increase in remnant level, or nonlinear power. This decrease in linearity is reflected both in the output magnitude spectra of the subjects, and in the linear fit of the amplitude ratio functions.
Feedback and rewards, part II: formal and informal feedback reviews.
Harolds, Jay
2013-02-01
There are 2 major classes of feedback. One class of feedback consists of the informal, numerous conversations between various people in the organization regarding the performance, behavior, and goals of an individual. Another class of feedback consists of formal reviews held once or twice a year between a supervisor and an individual. This article discusses both types of feedback.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Bakry, A.; Abdulrhmann, S.; Ahmed, M., E-mail: mostafa.farghal@mu.edu.eg
2016-06-15
We theoretically model the dynamics of semiconductor lasers subject to the double-reflector feedback. The proposed model is a new modification of the time-delay rate equations of semiconductor lasers under the optical feedback to account for this type of the double-reflector feedback. We examine the influence of adding the second reflector to dynamical states induced by the single-reflector feedback: periodic oscillations, period doubling, and chaos. Regimes of both short and long external cavities are considered. The present analyses are done using the bifurcation diagram, temporal trajectory, phase portrait, and fast Fourier transform of the laser intensity. We show that adding themore » second reflector attracts the periodic and perioddoubling oscillations, and chaos induced by the first reflector to a route-to-continuous-wave operation. During this operation, the periodic-oscillation frequency increases with strengthening the optical feedback. We show that the chaos induced by the double-reflector feedback is more irregular than that induced by the single-reflector feedback. The power spectrum of this chaos state does not reflect information on the geometry of the optical system, which then has potential for use in chaotic (secure) optical data encryption.« less
Accelerators for America's Future
NASA Astrophysics Data System (ADS)
Bai, Mei
2016-03-01
Particle accelerator, a powerful tool to energize beams of charged particles to a desired speed and energy, has been the working horse for investigating the fundamental structure of matter and fundermental laws of nature. Most known examples are the 2-mile long Stanford Linear Accelerator at SLAC, the high energy proton and anti-proton collider Tevatron at FermiLab, and Large Hadron Collider that is currently under operation at CERN. During the less than a century development of accelerator science and technology that led to a dazzling list of discoveries, particle accelerators have also found various applications beyond particle and nuclear physics research, and become an indispensible part of the economy. Today, one can find a particle accelerator at almost every corner of our lives, ranging from the x-ray machine at the airport security to radiation diagnostic and therapy in hospitals. This presentation will give a brief introduction of the applications of this powerful tool in fundermental research as well as in industry. Challenges in accelerator science and technology will also be briefly presented
Ion extraction capabilities of two-grid accelerator systems. [for spacecraft propulsion
NASA Technical Reports Server (NTRS)
Rovang, D. C.; Wilbur, P. J.
1984-01-01
An experimental investigation into the ion extraction capabilities of two-grid accelerator systems common to electrostatic ion thrusters is described. A large body of experimental data which facilitates the selection of the accelerator system geometries and operating parameters necessary to maximize the extracted ion current is presented. Results suggest that the impingement-limited perveance is not dramatically affected by reductions in screen hole diameter to 0.5 mm. Impingement-limited performance is shown to depend most strongly on grid separation distance, accelerator hole diameter ratio, the discharge-to-total accelerating voltage ratio, and the net-to-total accelerating voltage ratio. Results obtained at small grid separation ratios suggest a new grid operating condition where high beam current per hole levels are achieved at a specified net accelerating voltage. It is shown that this operating condition is realized at an optimum ratio of net-to-total accelerating voltage ratio which is typically quite high.
NASA Technical Reports Server (NTRS)
Moerder, Daniel D.
1987-01-01
A concept for optimally designing output feedback controllers for plants whose dynamics exhibit gross changes over their operating regimes was developed. This was to formulate the design problem in such a way that the implemented feedback gains vary as the output of a dynamical system whose independent variable is a scalar parameterization of the plant operating point. The results of this effort include derivation of necessary conditions for optimality for the general problem formulation, and for several simplified cases. The question of existence of a solution to the design problem was also examined, and it was shown that the class of gain variation schemes developed are capable of achieving gain variation histories which are arbitrarily close to the unconstrained gain solution for each point in the plant operating range. The theory was implemented in a feedback design algorithm, which was exercised in a numerical example. The results are applicable to the design of practical high-performance feedback controllers for plants whose dynamics vary significanly during operation. Many aerospace systems fall into this category.
Analysis and application of a velocity command motor as a reaction mass actuator
NASA Technical Reports Server (NTRS)
Sulla, Jeffrey L.; Juang, Jer-Nan; Horta, Lucas G.
1990-01-01
A commercially available linear stepper motor is applied as a reaction mass (RM) actuator. With the actuator operating in the (RM) relative-velocity command mode, open-loop and closed-loop testing is performed to determine operational limits. With the actuator mounted on a simple beam structure, root strain, RM acceleration, or beam acceleration is used in the feedback loop to augment the structural damping. The RM relative position is also used as feedback to ensure that the RM remains centered.
Written Corrective Feedback: Student Preferences and Teacher Feedback Practices
ERIC Educational Resources Information Center
Irwin, Bradley
2017-01-01
This case study explores the intricate interaction between students' preferences for written corrective feedback and actual teacher feedback practices in a second year academic EFL writing class in a Japanese university. Specific institutional and instructional details establish the context in which written feedback is being provided. A…
Breakthrough: Fermilab Accelerator Technology
None
2018-02-07
There are more than 30,000 particle accelerators in operation around the world. At Fermilab, scientists are collaborating with other laboratories and industry to optimize the manufacturing processes for a new type of powerful accelerator that uses superconducting niobium cavities. Experimenting with unique polishing materials, a Fermilab team has now developed an efficient and environmentally friendly way of creating cavities that can propel particles with more than 30 million volts per meter.
Breakthrough: Fermilab Accelerator Technology
DOE Office of Scientific and Technical Information (OSTI.GOV)
None
2012-04-23
There are more than 30,000 particle accelerators in operation around the world. At Fermilab, scientists are collaborating with other laboratories and industry to optimize the manufacturing processes for a new type of powerful accelerator that uses superconducting niobium cavities. Experimenting with unique polishing materials, a Fermilab team has now developed an efficient and environmentally friendly way of creating cavities that can propel particles with more than 30 million volts per meter.
Ion extraction capabilities of two-grid accelerator systems. M.S. Thesis
NASA Technical Reports Server (NTRS)
Rovang, D. C.; Wilbur, P. J.
1984-01-01
An experimental investigation into the ion extraction capabilities of two-grid accelerator systems common to electrostatic ion thrusters is described. This work resulted in a large body of experimental data which facilitates the selection of the accelerator system geometries and operating parameters necessary to maximize the extracted ion current. Results suggest that the impingement-limited perveance is not dramatically affected by reductions in screen hole diameter to 0.5 mm. Impingement-limited performance is shown to depend most strongly on grid separation distance, accelerator hole diameter ratio, the discharge-to-total accelerating voltage ratio, and the net-to-total accelerating voltage ratio. Results obtained at small grid separation ratios suggest a new grid operating condition where high beam current per hole levels are achieved at a specified net accelerating voltage. It is shown that this operating condition is realized at an optimum ratio of net-to-total accelerating voltage ratio which is typically quite high. The apparatus developed for this study is also shown to be well suited measuring the electron backstreaming and electrical breakdown characteristics of two-grid accelerator systems.
Feedback on Feedback Practice: Perceptions of Students and Academics
ERIC Educational Resources Information Center
Mulliner, Emma; Tucker, Matthew
2017-01-01
While feedback is widely considered central to student learning, students across the higher education sector commonly report dissatisfaction with the feedback they receive. In contrast, academics often feel they provide quality and informative feedback. This article explores and compares the perceptions of students and academics with regard to…
Period locking due to delayed feedback in a laser with saturable absorber.
Carr, T W
2003-08-01
We consider laser with saturable absorber operating in the pulsating regime that is subject to delayed feedback. Alone, both the saturable absorber and delayed feedback cause the clockwise output to become unstable to periodic output via Hopf bifurcations. The delay feedback causes the laser pulse period to lock to an integer fraction of the feedback time. We derive a map from the original model to describe the periodic pulsations of the laser. Equations for the period of the laser predict the occurrence of the different locking states as well as the value of the pump when there is a switch between the locked states.
NASA Astrophysics Data System (ADS)
Xu, Wei; Li, Jing-Yi; Huang, Sen-Lin; Z. Wu, W.; Hao, H.; P., Wang; K. Wu, Y.
2014-10-01
The Duke storage ring is a dedicated driver for the storage ring based oscillator free-electron lasers (FELs), and the High Intensity Gamma-ray Source (HIGS). It is operated with a beam current ranging from about 1 mA to 100 mA per bunch for various operations and accelerator physics studies. High performance operations of the FEL and γ-ray source require a stable electron beam orbit, which has been realized by the global orbit feedback system. As a critical part of the orbit feedback system, the electron beam position monitors (BPMs) are required to be able to precisely measure the electron beam orbit in a wide range of the single-bunch current. However, the high peak voltage of the BPM pickups associated with high single-bunch current degrades the performance of the BPM electronics, and can potentially damage the BPM electronics. A signal conditioning method using low pass filters is developed to reduce the peak voltage to protect the BPM electronics, and to make the BPMs capable of working with a wide range of single-bunch current. Simulations and electron beam based tests are performed. The results show that the Duke storage ring BPM system is capable of providing precise orbit measurements to ensure highly stable FEL and HIGS operations.
DOE Office of Scientific and Technical Information (OSTI.GOV)
De Doncker, R.W.A.A.
The direct (d) and quadrature (q) components of flux, as sensed by flux sensors or determined from voltage and current measurements in a direct field orientation scheme, are processed rapidly and accurately to provide flux amplitude and angular position values for use by the vector rotator of a universal field-oriented (UFO) controller. Flux amplitude (linear or squared) is provided as feedback to tune the UFO controller for operation in direct and indirect field orientation modes and enables smooth transitions from one mode to the other. 3 figs.
De Doncker, R.W.A.A.
1992-09-01
The direct (d) and quadrature (q) components of flux, as sensed by flux sensors or determined from voltage and current measurements in a direct field orientation scheme, are processed rapidly and accurately to provide flux amplitude and angular position values for use by the vector rotator of a universal field-oriented (UFO) controller. Flux amplitude (linear or squared) is provided as feedback to tune the UFO controller for operation in direct and indirect field orientation modes and enables smooth transitions from one mode to the other. 3 figs.
Development of bipolar-pulse accelerator for intense pulsed ion beam acceleration
NASA Astrophysics Data System (ADS)
Masugata, Katsumi; Shimizu, Yuichro; Fujioka, Yuhki; Kitamura, Iwao; Tanoue, Hisao; Arai, Kazuo
2004-12-01
To improve the purity of intense pulsed ion beams, a new type of pulsed ion beam accelerator named "bipolar pulse accelerator" was proposed. To confirm the principle of the accelerator a prototype of the experimental system was developed. The system utilizes By type magnetically insulated acceleration gap and operated with single polar negative pulse. A coaxial gas puff plasma gun was used as an ion source, which was placed inside the grounded anode. Source plasma (nitrogen) of current density ≈25 A/cm2, duration ≈1.5 μs was injected into the acceleration gap by the plasma gun. The ions were successfully accelerated from the grounded anode to the drift tube by applying negative pulse of voltage 240 kV, duration 100 ns to the drift tube. Pulsed ion beam of current density ≈40 A/cm2, duration ≈50 ns was obtained at 41 mm downstream from the anode surface. To evaluate the irradiation effect of the ion beam to solid material, an amorphous silicon thin film of thickness ≈500 nm was used as the target, which was deposited on the glass substrate. The film was found to be poly-crystallized after 4-shots of the pulsed nitrogen ion beam irradiation.
Longitudinal and transverse feedback kickers for the ALS
DOE Office of Scientific and Technical Information (OSTI.GOV)
Corlett, J.N.; Johnson, J.; Lambertson, G.
We describe the development of electromagnetic kickers for coupled-bunch feedback systems at the ALS. Transverse kickers are of a stripline design with one kicker per plane, operating in the baseband, 10 kHz to 250 MHz. Longitudinal lockers are of a coaxial design with electrodes paired in series operating over the band 1.00 to 1.25 GHz. Operating-band measurements and parasitic impedance measurements are presented. Power levels from beam induced signals are presented. Fabrication techniques are discussed.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hanson, D.L.; Cuneo, M.E.; McKay, P.F.
We present results from initial experiments with a high impedance applied-B extraction diode on the SABRE ten stage linear induction accelerator (6.7 MV, 300 kA). We have demonstrated efficient coupling of power from the accelerator through an extended MITL (Magnetically Insulated Transmission Line) into a high intensity ion beam. Both MITL electron flow in the diode region and ion diode behavior, including ion source turn-on, virtual cathode formation and evolution, enhancement delay, and ion coupling efficiency, are strongly influenced by the geometry of the diode insulating magnetic field. For our present diode electrode geometry, electrons from the diode feed stronglymore » influence the evolution of the virtual cathode. Both experimental data and particle-in-cell numerical simulations show that uniform insulation of these feed electrons is required for uniform ion emission and efficient diode operation.« less
Six axis force feedback input device
NASA Technical Reports Server (NTRS)
Ohm, Timothy (Inventor)
1998-01-01
The present invention is a low friction, low inertia, six-axis force feedback input device comprising an arm with double-jointed, tendon-driven revolute joints, a decoupled tendon-driven wrist, and a base with encoders and motors. The input device functions as a master robot manipulator of a microsurgical teleoperated robot system including a slave robot manipulator coupled to an amplifier chassis, which is coupled to a control chassis, which is coupled to a workstation with a graphical user interface. The amplifier chassis is coupled to the motors of the master robot manipulator and the control chassis is coupled to the encoders of the master robot manipulator. A force feedback can be applied to the input device and can be generated from the slave robot to enable a user to operate the slave robot via the input device without physically viewing the slave robot. Also, the force feedback can be generated from the workstation to represent fictitious forces to constrain the input device's control of the slave robot to be within imaginary predetermined boundaries.
Frontier applications of electrostatic accelerators
NASA Astrophysics Data System (ADS)
Liu, Ke-Xin; Wang, Yu-Gang; Fan, Tie-Shuan; Zhang, Guo-Hui; Chen, Jia-Er
2013-10-01
Electrostatic accelerator is a powerful tool in many research fields, such as nuclear physics, radiation biology, material science, archaeology and earth sciences. Two electrostatic accelerators, one is the single stage Van de Graaff with terminal voltage of 4.5 MV and another one is the EN tandem with terminal voltage of 6 MV, were installed in 1980s and had been put into operation since the early 1990s at the Institute of Heavy Ion Physics. Many applications have been carried out since then. These two accelerators are described and summaries of the most important applications on neutron physics and technology, radiation biology and material science, as well as accelerator mass spectrometry (AMS) are presented.
Television-optical operational amplifier.
Goetz, J; Häusler, G; Sesselmann, R
1979-08-15
The advantages of negative feedback are well known in electronics and extensively used in the operational amplifier. The properties of such a system are nearly independent of the parameters in the forward branch of the system; they are only determined by external elements in the backward branch. An optical analog of such an operational amplifier is reported. The essential operations, amplifications, and inversion of the circulating signals are carried out using a TV system. The capability of the system to compensate for spatial inhomogeneities and for nonlinearities is demonstrated. In addition, the system is able to create the inverse of a transfer function located in the feedback branch.
Model-independent particle accelerator tuning
Scheinker, Alexander; Pang, Xiaoying; Rybarcyk, Larry
2013-10-21
We present a new model-independent dynamic feedback technique, rotation rate tuning, for automatically and simultaneously tuning coupled components of uncertain, complex systems. The main advantages of the method are: 1) It has the ability to handle unknown, time-varying systems, 2) It gives known bounds on parameter update rates, 3) We give an analytic proof of its convergence and its stability, and 4) It has a simple digital implementation through a control system such as the Experimental Physics and Industrial Control System (EPICS). Because this technique is model independent it may be useful as a real-time, in-hardware, feedback-based optimization scheme formore » uncertain and time-varying systems. In particular, it is robust enough to handle uncertainty due to coupling, thermal cycling, misalignments, and manufacturing imperfections. As a result, it may be used as a fine-tuning supplement for existing accelerator tuning/control schemes. We present multi-particle simulation results demonstrating the scheme’s ability to simultaneously adaptively adjust the set points of twenty two quadrupole magnets and two RF buncher cavities in the Los Alamos Neutron Science Center Linear Accelerator’s transport region, while the beam properties and RF phase shift are continuously varying. The tuning is based only on beam current readings, without knowledge of particle dynamics. We also present an outline of how to implement this general scheme in software for optimization, and in hardware for feedback-based control/tuning, for a wide range of systems.« less
An improved car-following model with multiple preceding cars' velocity fluctuation feedback
NASA Astrophysics Data System (ADS)
Guo, Lantian; Zhao, Xiangmo; Yu, Shaowei; Li, Xiuhai; Shi, Zhongke
2017-04-01
In order to explore and evaluate the effects of velocity variation trend of multiple preceding cars used in the Cooperative Adaptive Cruise Control (CACC) strategy on the dynamic characteristic, fuel economy and emission of the corresponding traffic flow, we conduct a study as follows: firstly, with the real-time car-following (CF) data, the close relationship between multiple preceding cars' velocity fluctuation feedback and the host car's behaviors is explored, the evaluation results clearly show that multiple preceding cars' velocity fluctuation with different time window-width are highly correlated to the host car's acceleration/deceleration. Then, a microscopic traffic flow model is proposed to evaluate the effects of multiple preceding cars' velocity fluctuation feedback in the CACC strategy on the traffic flow evolution process. Finally, numerical simulations on fuel economy and exhaust emission of the traffic flow are also implemented by utilizing VT-micro model. Simulation results prove that considering multiple preceding cars' velocity fluctuation feedback in the control strategy of the CACC system can improve roadway traffic mobility, fuel economy and exhaust emission performance.
Testing of a Loop Heat Pipe Subjected to Variable Accelerating Forces
NASA Technical Reports Server (NTRS)
Ku, Jentung; Ottenstein, Laura; Kaya, Tarik; Rogers, Paul; Hoff, Craig
2000-01-01
This paper presents viewgraphs of the functionality of a loop heat pipe that was subjected to variable accelerating forces. The topics include: 1) Summary of LHP (Loop Heat Pipe) Design Parameters; 2) Picture of the LHP; 3) Schematic of Test Setup; 4) Test Configurations; 5) Test Profiles; 6) Overview of Test Results; 7) Start-up; 8) Typical Start-up without Temperature Overshoot; 9) Start-up with a Large Temperature Overshoot; 10) LHP Operation Under Stationary Condition; 11) LHP Operation Under Continuous Acceleration; 12) LHP Operation Under Periodic Acceleration; 13) Effects of Acceleration on Temperature Oscillation and Hysteresis; 14) Temperature Oscillation/Hysteresis vs Spin Rate; and 15) Summary.
NASA Technical Reports Server (NTRS)
Banks, H. T.; Ito, K.
1991-01-01
A hybrid method for computing the feedback gains in linear quadratic regulator problem is proposed. The method, which combines use of a Chandrasekhar type system with an iteration of the Newton-Kleinman form with variable acceleration parameter Smith schemes, is formulated to efficiently compute directly the feedback gains rather than solutions of an associated Riccati equation. The hybrid method is particularly appropriate when used with large dimensional systems such as those arising in approximating infinite-dimensional (distributed parameter) control systems (e.g., those governed by delay-differential and partial differential equations). Computational advantages of the proposed algorithm over the standard eigenvector (Potter, Laub-Schur) based techniques are discussed, and numerical evidence of the efficacy of these ideas is presented.
Virtual grasping: closed-loop force control using electrotactile feedback.
Jorgovanovic, Nikola; Dosen, Strahinja; Djozic, Damir J; Krajoski, Goran; Farina, Dario
2014-01-01
Closing the control loop by providing somatosensory feedback to the user of a prosthesis is a well-known, long standing challenge in the field of prosthetics. Various approaches have been investigated for feedback restoration, ranging from direct neural stimulation to noninvasive sensory substitution methods. Although there are many studies presenting closed-loop systems, only a few of them objectively evaluated the closed-loop performance, mostly using vibrotactile stimulation. Importantly, the conclusions about the utility of the feedback were partly contradictory. The goal of the current study was to systematically investigate the capability of human subjects to control grasping force in closed loop using electrotactile feedback. We have developed a realistic experimental setup for virtual grasping, which operated in real time, included a set of real life objects, as well as a graphical and dynamical model of the prosthesis. We have used the setup to test 10 healthy, able bodied subjects to investigate the role of training, feedback and feedforward control, robustness of the closed loop, and the ability of the human subjects to generalize the control to previously "unseen" objects. Overall, the outcomes of this study are very optimistic with regard to the benefits of feedback and reveal various, practically relevant, aspects of closed-loop control.
Study on real-time force feedback for a master-slave interventional surgical robotic system.
Guo, Shuxiang; Wang, Yuan; Xiao, Nan; Li, Youxiang; Jiang, Yuhua
2018-04-13
In robot-assisted catheterization, haptic feedback is important, but is currently lacking. In addition, conventional interventional surgical robotic systems typically employ a master-slave architecture with an open-loop force feedback, which results in inaccurate control. We develop herein a novel real-time master-slave (RTMS) interventional surgical robotic system with a closed-loop force feedback that allows a surgeon to sense the true force during remote operation, provide adequate haptic feedback, and improve control accuracy in robot-assisted catheterization. As part of this system, we also design a unique master control handle that measures the true force felt by a surgeon, providing the basis for the closed-loop control of the entire system. We use theoretical and empirical methods to demonstrate that the proposed RTMS system provides a surgeon (using the master control handle) with a more accurate and realistic force sensation, which subsequently improves the precision of the master-slave manipulation. The experimental results show a substantial increase in the control accuracy of the force feedback and an increase in operational efficiency during surgery.
Application of particle accelerators in research.
Mazzitelli, Giovanni
2011-07-01
Since the beginning of the past century, accelerators have started to play a fundamental role as powerful tools to discover the world around us, how the universe has evolved since the big bang and to develop fundamental instruments for everyday life. Although more than 15 000 accelerators are operating around the world only a very few of them are dedicated to fundamental research. An overview of the present high energy physics (HEP) accelerator status and prospectives is presented.
The purpose of this SOP is to describe the steps involved in cleaning the electronic data generated from data entry of the Questionnaire Feedback form. It applies to electronic data corresponding to the Questionnaire Feedback form that was scanned and verified by the data staff ...
SAMS Acceleration Measurements on MIR
NASA Technical Reports Server (NTRS)
Moskowitz, Milton E.; Hrovat, Kenneth; Finkelstein, Robert; Reckart, Timothy
1997-01-01
During NASA Increment 3 (September 1996 to January 1997), about 5 gigabytes of acceleration data were collected by the Space Acceleration Measurement System (SAMS) onboard the Russian Space Station, Mir. The data were recorded on 11 optical disks and were returned to Earth on STS-81. During this time, SAMS data were collected in the Priroda module to support the following experiments: the Mir Structural Dynamics Experiment (MiSDE) and Binary Colloidal Alloy Tests (BCAT). This report points out some of the salient features of the microgravity environment to which these experiments were exposed. Also documented are mission events of interest such as the docked phase of STS-81 operations, a Progress engine burn, attitude control thruster operation, and crew exercise. Also included are a description of the Mir module orientations, and the panel notations within the modules. This report presents an overview of the SAMS acceleration measurements recorded by 10 Hz and 100 Hz sensor heads. Variations in the acceleration environment caused by unique activities such as crew exercise and life-support fans are presented. The analyses included herein complement those presented in previous mission summary reports published by the Principal Investigator Microgravity Services (PIMS) group.
The Timing of Feedback on Mathematics Problem Solving in a Classroom Setting
ERIC Educational Resources Information Center
Fyfe, Emily R.; Rittle-Johnson, Bethany
2015-01-01
Feedback is a ubiquitous learning tool that is theorized to help learners detect and correct their errors. The goal of this study was to examine the effects of feedback in a classroom context for children solving math equivalence problems (problems with operations on both sides of the equal sign). The authors worked with children in 7 second-grade…
NASA Astrophysics Data System (ADS)
Dubinov, Alexander E.; Ochkina, Elena I.
2018-05-01
State-of-the-art compact recirculating electron accelerators operating at intermediate energies (tens of MeV) are reviewed. The acceleration schemes implemented in the rhodotron, ridgetron, fantron, and cylindertron machines are discussed. Major accelerator components such as the electron guns, accelerating cavities, and bending magnets are described. The parameters of currently operating recirculating accelerators are tabulated, and applications of these accelerators in different processes of irradiation are exemplified.
Multitask neurovision processor with extensive feedback and feedforward connections
NASA Astrophysics Data System (ADS)
Gupta, Madan M.; Knopf, George K.
1991-11-01
A multi-task neuro-vision parameter which performs a variety of information processing operations associated with the early stages of biological vision is presented. The network architecture of this neuro-vision processor, called the positive-negative (PN) neural processor, is loosely based on the neural activity fields exhibited by thalamic and cortical nervous tissue layers. The computational operation performed by the processor arises from the strength of the recurrent feedback among the numerous positive and negative neural computing units. By adjusting the feedback connections it is possible to generate diverse dynamic behavior that may be used for short-term visual memory (STVM), spatio-temporal filtering (STF), and pulse frequency modulation (PFM). The information attributes that are to be processes may be regulated by modifying the feedforward connections from the signal space to the neural processor.
Using Feedback to Promote Physical Activity: The Role of the Feedback Sign
Kramer, Jan-Niklas
2017-01-01
Background Providing feedback is a technique to promote health behavior that is emphasized by behavior change theories. However, these theories make contradicting predictions regarding the effect of the feedback sign—that is, whether the feedback signals success or failure. Thus, it is unclear whether positive or negative feedback leads to more favorable behavior change in a health behavior intervention. Objective The aim of this study was to examine the effect of the feedback sign in a health behavior change intervention. Methods Data from participants (N=1623) of a 6-month physical activity intervention was used. Participants received a feedback email at the beginning of each month. Feedback was either positive or negative depending on the participants’ physical activity in the previous month. In an exploratory analysis, change in monthly step count averages was used to evaluate the feedback effect. Results The feedback sign did not predict the change in monthly step count averages over the course of the intervention (b=−84.28, P=.28). Descriptive differences between positive and negative feedback can be explained by regression to the mean. Conclusions The feedback sign might not influence the effect of monthly feedback emails sent out to participants of a large-scale physical activity intervention. However, randomized studies are needed to further support this conclusion. Limitations as well as opportunities for future research are discussed. PMID:28576757
Biocybernetic system evaluates indices of operator engagement in automated task
NASA Technical Reports Server (NTRS)
Pope, A. T.; Bogart, E. H.; Bartolome, D. S.
1995-01-01
A biocybernetic system has been developed as a method to evaluate automated flight deck concepts for compatibility with human capabilities. A biocybernetic loop is formed by adjusting the mode of operation of a task set (e.g., manual/automated mix) based on electroencephalographic (EEG) signals reflecting an operator's engagement in the task set. A critical issue for the loop operation is the selection of features of the EEG to provide an index of engagement upon which to base decisions to adjust task mode. Subjects were run in the closed-loop feedback configuration under four candidate and three experimental control definitions of an engagement index. The temporal patterning of system mode switching was observed for both positive and negative feedback of the index. The indices were judged on the basis of their relative strength in exhibiting expected feedback control system phenomena (stable operation under negative feedback and unstable operation under positive feedback). Of the candidate indices evaluated in this study, an index constructed according to the formula, beta power/(alpha power + theta power), reflected task engagement best.
Space Acceleration Measurement System-II
NASA Technical Reports Server (NTRS)
Foster, William
2009-01-01
Space Acceleration Measurement System (SAMS-II) is an ongoing study of the small forces (vibrations and accelerations) on the ISS that result from the operation of hardware, crew activities, as well as dockings and maneuvering. Results will be used to generalize the types of vibrations affecting vibration-sensitive experiments. Investigators seek to better understand the vibration environment on the space station to enable future research.
Effects of invalid feedback on learning and feedback-related brain activity in decision-making.
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. Copyright © 2015 Elsevier Inc. All rights reserved.
The mechatronic design of a fast wire scanner in IHEP U-70 accelerator
NASA Astrophysics Data System (ADS)
Baranov, V. T.; Makhov, S. S.; Savin, D. A.; Terekhov, V. I.
2016-10-01
This paper presents the mechatronic design of a fast wire scanner based on a servomotor. The design of the wire scanner is motivated by the need to measure the transverse profile of the high power proton and carbon beams at the IHEP U-70 accelerator. This paper formulates the requirements to the fast wire scanner system for the high intensity proton beam at the U-70 accelerator. The results on the design of electro-mechanical device for the wire scanner with a wire traveling speed 10-20 m/s are presented. The solution consists in a brushless servomotor and standard motor control electronics. High radiation levels in the accelerator enclosure dictate the use of a resolver as the position feedback element.
Experiments evaluating compliance and force feedback effect on manipulator performance
NASA Technical Reports Server (NTRS)
Kugath, D. A.
1972-01-01
The performance capability was assessed of operators performing simulated space tasks using manipulator systems which had compliance and force feedback varied. Two manipulators were used, the E-2 electromechanical man-equivalent (force, reach, etc.) master-slave system and a modified CAM 1400 hydraulic master-slave with 100 lbs force capability at reaches of 24 ft. The CAM 1400 was further modified to operate without its normal force feedback. Several experiments and simulations were performed. The first two involved the E-2 absorbing the energy of a moving mass and secondly, guiding a mass thru a maze. Thus, both work and self paced tasks were studied as servo compliance was varied. Three simulations were run with the E-2 mounted on the CAM 1400 to evaluate the concept of a dexterous manipulator as an end effector of a boom-manipulator. Finally, the CAM 1400 performed a maze test and also simulated the capture of a large mass as the servo compliance was varied and with force feedback included and removed.
A novel electron accelerator for MRI-Linac radiotherapy.
Whelan, Brendan; Gierman, Stephen; Holloway, Lois; Schmerge, John; Keall, Paul; Fahrig, Rebecca
2016-03-01
MRI guided radiotherapy is a rapidly growing field; however, current electron accelerators are not designed to operate in the magnetic fringe fields of MRI scanners. As such, current MRI-Linac systems require magnetic shielding, which can degrade MR image quality and limit system flexibility. The purpose of this work was to develop and test a novel medical electron accelerator concept which is inherently robust to operation within magnetic fields for in-line MRI-Linac systems. Computational simulations were utilized to model the accelerator, including the thermionic emission process, the electromagnetic fields within the accelerating structure, and resulting particle trajectories through these fields. The spatial and energy characteristics of the electron beam were quantified at the accelerator target and compared to published data for conventional accelerators. The model was then coupled to the fields from a simulated 1 T superconducting magnet and solved for cathode to isocenter distances between 1.0 and 2.4 m; the impact on the electron beam was quantified. For the zero field solution, the average current at the target was 146.3 mA, with a median energy of 5.8 MeV (interquartile spread of 0.1 MeV), and a spot size diameter of 1.5 mm full-width-tenth-maximum. Such an electron beam is suitable for therapy, comparing favorably to published data for conventional systems. The simulated accelerator showed increased robustness to operation in in-line magnetic fields, with a maximum current loss of 3% compared to 85% for a conventional system in the same magnetic fields. Computational simulations suggest that replacing conventional DC electron sources with a RF based source could be used to develop medical electron accelerators which are robust to operation in in-line magnetic fields. This would enable the development of MRI-Linac systems with no magnetic shielding around the Linac and reduce the requirements for optimization of magnetic fringe field, simplify design of
A novel electron accelerator for MRI-Linac radiotherapy
Whelan, Brendan; Gierman, Stephen; Holloway, Lois; Schmerge, John; Keall, Paul; Fahrig, Rebecca
2016-01-01
Purpose: MRI guided radiotherapy is a rapidly growing field; however, current electron accelerators are not designed to operate in the magnetic fringe fields of MRI scanners. As such, current MRI-Linac systems require magnetic shielding, which can degrade MR image quality and limit system flexibility. The purpose of this work was to develop and test a novel medical electron accelerator concept which is inherently robust to operation within magnetic fields for in-line MRI-Linac systems. Methods: Computational simulations were utilized to model the accelerator, including the thermionic emission process, the electromagnetic fields within the accelerating structure, and resulting particle trajectories through these fields. The spatial and energy characteristics of the electron beam were quantified at the accelerator target and compared to published data for conventional accelerators. The model was then coupled to the fields from a simulated 1 T superconducting magnet and solved for cathode to isocenter distances between 1.0 and 2.4 m; the impact on the electron beam was quantified. Results: For the zero field solution, the average current at the target was 146.3 mA, with a median energy of 5.8 MeV (interquartile spread of 0.1 MeV), and a spot size diameter of 1.5 mm full-width-tenth-maximum. Such an electron beam is suitable for therapy, comparing favorably to published data for conventional systems. The simulated accelerator showed increased robustness to operation in in-line magnetic fields, with a maximum current loss of 3% compared to 85% for a conventional system in the same magnetic fields. Conclusions: Computational simulations suggest that replacing conventional DC electron sources with a RF based source could be used to develop medical electron accelerators which are robust to operation in in-line magnetic fields. This would enable the development of MRI-Linac systems with no magnetic shielding around the Linac and reduce the requirements for optimization of
French Atomic Energy Commission Decommissioning Programme and Feedback Experience - 12230
DOE Office of Scientific and Technical Information (OSTI.GOV)
Guiberteau, Ph.; Nokhamzon, J.G.
Since the French Atomic and Alternatives Energy Commission (CEA) was founded in 1945 to carry out research programmes on use of nuclear, and its application France has set up and run various types of installations: research or prototypes reactors, process study or examination laboratories, pilot installations, accelerators, nuclear power plants and processing facilities. Some of these are currently being dismantled or must be dismantled soon so that the DEN, the Nuclear Energy Division, can construct new equipment and thus have available a range of R and D facilities in line with the issues of the nuclear industry of the future.more » Since the 1960's and 1970's in all its centres, the CEA has acquired experience and know-how through dismantling various nuclear facilities. The dismantling techniques are nowadays operational, even if sometimes certain specific developments are necessary to reduce the cost of operations. Thanks to availability of techniques and guarantees of dismantling programme financing now from two dedicated funds, close to euro 15,000 M for the next thirty years, for current or projected dismantling operations, the CEA's Nuclear Energy Division has been able to develop, when necessary, its immediate dismantling strategy. Currently, nearly thirty facilities are being dismantled by the CEA's Nuclear Energy Division operational units with industrial partners. Thus the next decade will see completion of the dismantling and radioactive clean-up of the Grenoble site and of the facilities on the Fontenay-aux-Roses site. By 2016, the dismantling of the UP1 plant at Marcoule, the largest dismantling work in France, will be well advanced, with all the process equipment dismantled. After an overview of the French regulatory framework, the paper will describe the DD and R (Decontamination Decommissioning and Remediation) strategy, programme and feedback experience inside the CEA's Nuclear Energy Division. A special feature of dismantling operations at the
Quantum theory of multiple-input-multiple-output Markovian feedback with diffusive measurements
DOE Office of Scientific and Technical Information (OSTI.GOV)
Chia, A.; Wiseman, H. M.
2011-07-15
Feedback control engineers have been interested in multiple-input-multiple-output (MIMO) extensions of single-input-single-output (SISO) results of various kinds due to its rich mathematical structure and practical applications. An outstanding problem in quantum feedback control is the extension of the SISO theory of Markovian feedback by Wiseman and Milburn [Phys. Rev. Lett. 70, 548 (1993)] to multiple inputs and multiple outputs. Here we generalize the SISO homodyne-mediated feedback theory to allow for multiple inputs, multiple outputs, and arbitrary diffusive quantum measurements. We thus obtain a MIMO framework which resembles the SISO theory and whose additional mathematical structure is highlighted by the extensivemore » use of vector-operator algebra.« less
Ruiz de Gauna, Sofía; González-Otero, Digna M.; Ruiz, Jesus; Russell, James K.
2016-01-01
Background Quality of cardiopulmonary resuscitation (CPR) is key to increase survival from cardiac arrest. Providing chest compressions with adequate rate and depth is difficult even for well-trained rescuers. The use of real-time feedback devices is intended to contribute to enhance chest compression quality. These devices are typically based on the double integration of the acceleration to obtain the chest displacement during compressions. The integration process is inherently unstable and leads to important errors unless boundary conditions are applied for each compression cycle. Commercial solutions use additional reference signals to establish these conditions, requiring additional sensors. Our aim was to study the accuracy of three methods based solely on the acceleration signal to provide feedback on the compression rate and depth. Materials and Methods We simulated a CPR scenario with several volunteers grouped in couples providing chest compressions on a resuscitation manikin. Different target rates (80, 100, 120, and 140 compressions per minute) and a target depth of at least 50 mm were indicated. The manikin was equipped with a displacement sensor. The accelerometer was placed between the rescuer’s hands and the manikin’s chest. We designed three alternatives to direct integration based on different principles (linear filtering, analysis of velocity, and spectral analysis of acceleration). We evaluated their accuracy by comparing the estimated depth and rate with the values obtained from the reference displacement sensor. Results The median (IQR) percent error was 5.9% (2.8–10.3), 6.3% (2.9–11.3), and 2.5% (1.2–4.4) for depth and 1.7% (0.0–2.3), 0.0% (0.0–2.0), and 0.9% (0.4–1.6) for rate, respectively. Depth accuracy depended on the target rate (p < 0.001) and on the rescuer couple (p < 0.001) within each method. Conclusions Accurate feedback on chest compression depth and rate during CPR is possible using exclusively the chest
Preliminary Airspace Operations Simulations Findings Report
NASA Technical Reports Server (NTRS)
2005-01-01
Provides preliminary findings of the initial series (normal operations and contingency management) of airspace operations simulations. The key elements of this report discuss feedback from controller subjects for UAS flight above FL430. Findings provide initial evaluation of routine UAS operations above dense ARTCC airspace (ZOB), and identify areas of further research, policy direction and procedural development. This document further serves as an addendum to the detailed AOS simulation plan (Deliverable SIM001), incorporating feedback from FAA air traffic personnel and Access 5 IPTs.
[Accelerated postoperative recovery after colorectal surgery].
Alfonsi, P; Schaack, E
2007-01-01
Accelerated recovery programs are clinical pathways which outline the stages, and streamline the means, and techniques aiming toward the desired end a rapid return of the patient to his pre-operative physical and psychological status. Recovery from colo-rectal surgery may be slowed by the patient's general health, surgical stress, post-surgical pain, and post-operative ileus. Both surgeons and anesthesiologists participate throughout the peri-operative period in a clinical pathway aimed at minimizing these delaying factors. Key elements of this pathway include avoidance of pre-operative colonic cleansing, early enteral feeding, and effective post-operative pain management permitting early ambulation (usually via thoracic epidural anesthesia). Pre-operative information and motivation of the patient is also a key to the success of this accelerated recovery program. Studies of such programs have shown decreased duration of post-operative ileus and hospital stay without an increase in complications or re-admissions. The elements of the clinical pathway must be regularly re-evaluated and updated according to local experience and published data.
Coaxial needle insertion assistant with enhanced force feedback.
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.
Field stabilization studies for a radio frequency quadrupole accelerator
NASA Astrophysics Data System (ADS)
Gaur, R.; Kumar, V.
2014-07-01
The Radio Frequency Quadrupole (RFQ) linear accelerator is an accelerator that efficiently focuses, bunches and accelerates a high intensity DC beam from an ion source, for various applications. Unlike other conventional RF linear accelerators, the electromagnetic mode used for its operation is not the lowest frequency mode supported by the structure. In a four vane type RFQ, there are several undesired electromagnetic modes having frequency close to that of the operating mode. While designing an RFQ accelerator, care must be taken to ensure that the frequencies of these nearby modes are sufficiently separated from the operating mode. If the undesired nearby modes have frequencies close to the operating mode, the electromagnetic field pattern in the presence of geometrical errors will not be stabilized to the desired field profile, and will be perturbed by the nearby modes. This will affect the beam dynamics and reduce the beam transmission. In this paper, we present a detailed study of the electromagnetic modes supported, which is followed by calculations for implementation of suitable techniques to make the desired operating mode stable against mixing with unwanted modes for an RFQ being designed for the proposed Indian Spallation Neutron Source (ISNS) project at Raja Ramanna Centre for Advanced Technology, Indore. Resonant coupling scheme, along with dipole stabilization rods has been proposed to increase the mode separation. The paper discusses the details of a generalized optimization procedure that has been used for the design of mode stabilization scheme.
NASA Technical Reports Server (NTRS)
Banks, H. T.; Rosen, I. G.
1984-01-01
Approximation ideas are discussed that can be used in parameter estimation and feedback control for Euler-Bernoulli models of elastic systems. Focusing on parameter estimation problems, ways by which one can obtain convergence results for cubic spline based schemes for hybrid models involving an elastic cantilevered beam with tip mass and base acceleration are outlined. Sample numerical findings are also presented.
Wu, Ziran; Lee, Chunghun H.; Wootton, Kent P.; ...
2016-03-01
Silicon woodpile photonic crystals provide a base structure that can be used to build a three-dimensional dielectric waveguide system for high-gradient laser driven acceleration. A new woodpile waveguide design that hosts a phase synchronous, centrally confined accelerating mode is proposed. Comparing with previously discovered silicon woodpile accelerating modes, this mode shows advantages in terms of better electron beam loading and higher achievable acceleration gradient. Several traveling-wave coupler design schemes developed for multi-cell RF cavity accelerators are adapted to the woodpile power coupler design for this new accelerating mode. Design of a forward coupled, highly efficient silicon woodpile accelerator is achieved.more » Simulation shows high efficiency of over 75% of the drive laser power coupled to this fundamental accelerating mode, with less than 15% backward wave scattering. The estimated acceleration gradient, when the coupler structure is driven at the damage threshold fluence of silicon at its operating 1.506 μm wavelength, can reach 185 MV/m. Lastly, a 17-layer woodpile waveguide structure was successfully fabricated, and the measured bandgap is in excellent agreement with simulation.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wu, Ziran; Lee, Chunghun H.; Wootton, Kent P.
Silicon woodpile photonic crystals provide a base structure that can be used to build a three-dimensional dielectric waveguide system for high-gradient laser driven acceleration. A new woodpile waveguide design that hosts a phase synchronous, centrally confined accelerating mode is proposed. Comparing with previously discovered silicon woodpile accelerating modes, this mode shows advantages in terms of better electron beam loading and higher achievable acceleration gradient. Several traveling-wave coupler design schemes developed for multi-cell RF cavity accelerators are adapted to the woodpile power coupler design for this new accelerating mode. Design of a forward coupled, highly efficient silicon woodpile accelerator is achieved.more » Simulation shows high efficiency of over 75% of the drive laser power coupled to this fundamental accelerating mode, with less than 15% backward wave scattering. The estimated acceleration gradient, when the coupler structure is driven at the damage threshold fluence of silicon at its operating 1.506 μm wavelength, can reach 185 MV/m. Lastly, a 17-layer woodpile waveguide structure was successfully fabricated, and the measured bandgap is in excellent agreement with simulation.« less
Individualized feedback during simulated laparoscopic training: a mixed methods study
Weurlander, Maria; Hedman, Leif; Nisell, Henry; Lindqvist, Pelle G.; Felländer-Tsai, Li; Enochsson, Lars
2015-01-01
Objectives This study aimed to explore the value of indi-vidualized feedback on performance, flow and self-efficacy during simulated laparoscopy. Furthermore, we wished to explore attitudes towards feedback and simulator training among medical students. Methods Sixteen medical students were included in the study and randomized to laparoscopic simulator training with or without feedback. A teacher provided individualized feedback continuously throughout the procedures to the target group. Validated questionnaires and scales were used to evaluate self-efficacy and flow. The Mann-Whitney U test was used to evaluate differences between groups regarding laparoscopic performance (instrument path length), self-efficacy and flow. Qualitative data was collected by group interviews and interpreted using inductive thematic analyses. Results Sixteen students completed the simulator training and questionnaires. Instrument path length was shorter in the feedback group (median 3.9 m; IQR: 3.3-4.9) as com-pared to the control group (median 5.9 m; IQR: 5.0-8.1), p<0.05. Self-efficacy improved in both groups. Eleven students participated in the focus interviews. Participants in the control group expressed that they had fun, whereas participants in the feedback group were more concentrated on the task and also more anxious. Both groups had high ambitions to succeed and also expressed the importance of getting feedback. The authenticity of the training scenario was important for the learning process. Conclusions This study highlights the importance of individualized feedback during simulated laparoscopy training. The next step is to further optimize feedback and to transfer standardized and individualized feedback from the simulated setting to the operating room. PMID:26223033
Accelerated deflation promotes homogeneous airspace liquid distribution in the edematous lung.
Wu, You; Nguyen, Tam L; Perlman, Carrie E
2017-04-01
Edematous lungs contain regions with heterogeneous alveolar flooding. Liquid is trapped in flooded alveoli by a pressure barrier-higher liquid pressure at the border than in the center of flooded alveoli-that is proportional to surface tension, T Stress is concentrated between aerated and flooded alveoli, to a degree proportional to T Mechanical ventilation, by cyclically increasing T , injuriously exacerbates stress concentrations. Overcoming the pressure barrier to redistribute liquid more homogeneously between alveoli should reduce stress concentration prevalence and ventilation injury. In isolated rat lungs, we test whether accelerated deflation can overcome the pressure barrier and catapult liquid out of flooded alveoli. We generate a local edema model with normal T by microinfusing liquid into surface alveoli. We generate a global edema model with high T by establishing hydrostatic edema, which does not alter T , and then gently ventilating the edematous lungs, which increases T at 15 cmH 2 O transpulmonary pressure by 52%. Thus ventilation of globally edematous lungs increases T , which should increase stress concentrations and, with positive feedback, cause escalating ventilation injury. In the local model, when the pressure barrier is moderate, accelerated deflation causes liquid to escape from flooded alveoli and redistribute more equitably. Flooding heterogeneity tends to decrease. In the global model, accelerated deflation causes liquid escape, but-because of elevated T -the liquid jumps to nearby, aerated alveoli. Flooding heterogeneity is unaltered. In pulmonary edema with normal T , early ventilation with accelerated deflation might reduce the positive feedback mechanism through which ventilation injury increases over time. NEW & NOTEWORTHY We introduce, in the isolated rat lung, a new model of pulmonary edema with elevated surface tension. We first generate hydrostatic edema and then ventilate gently to increase surface tension. We investigate the
The purpose of this SOP is to describe the coding strategy for the Questionnaire Feedback form. This Questionnaire Feedback form was developed for use during the Arizona NHEXAS project and the Border study. Keywords: data; coding; questionnaire feedback form.
The U.S.-Mexico B...
A cascade feedback control approach for hypnosis.
Puebla, Hector; Alvarez-Ramírez, José
2005-10-01
This article studies the problem of controlling the drug administration during an anesthesia process, where muscle relaxation, analgesia, and hypnosis are regulated by means of monitored administration of specific drugs. On the basis of a seventh-order nonlinear pharmacokinetic-pharmacodynamic representation of the hypnosis process dynamics, a cascade (master/slave) feedback control structure for controlling the bispectral index (BIS) is proposed. The master controller compares the measured BIS with its reference value to provide the expired isoflurane concentration reference to the slave controller. In turn, the slave controller manipulates the anesthetic isoflurane concentration entering the anesthetic system to achieve the reference from the master controller. The advantage of the proposed cascade control structure with respect to its noncascade counterpart is that the former provides operation protection against BIS measurement failures. In fact, under a BIS measurement fault, the master control feedback is broken and the slave controller operates under a safe reference value. Extensive numerical simulations are used to illustrate the functioning of the proposed cascade control structure.
González-Otero, Digna M; de Gauna, Sofía Ruiz; Ruiz, Jesus; Rivero, Raquel; Gutierrez, J J; Saiz, Purificación; Russell, James K
2018-04-20
Out-of-hospital cardiac arrest is common in public locations, including public transportation sites. Feedback devices are increasingly being used to improve chest-compression quality. However, their performance during public transportation has not been studied yet. To test two CPR feedback devices representative of the current technologies (accelerometer and electromag- netic-field) in a long-distance train. Volunteers applied compressions on a manikin during the train route using both feedback devices. Depth and rate measurements computed by the devices were compared to the gold-standard values. Sixty-four 4-min records were acquired. The accelerometer-based device provided visual help in all experiments. Median absolute errors in depth and rate were 2.4 mm and 1.3 compressions per minute (cpm) during conventional speed, and 2.5 mm and 1.2 cpm during high speed. The electromagnetic-field-based device never provided CPR feedback; alert messages were shown instead. However, measurements were stored in its internal memory. Absolute errors for depth and rate were 2.6 mm and 0.7 cpm during conventional speed, and 2.6 mm and 0.7 cpm during high speed. Both devices were accurate despite the accelerations and the electromagnetic interferences induced by the train. However, the electromagnetic-field-based device would require modifications to avoid excessive alerts impeding feedback.
High Gradient Accelerator Research
DOE Office of Scientific and Technical Information (OSTI.GOV)
Temkin, Richard
The goal of the MIT program of research on high gradient acceleration is the development of advanced acceleration concepts that lead to a practical and affordable next generation linear collider at the TeV energy level. Other applications, which are more near-term, include accelerators for materials processing; medicine; defense; mining; security; and inspection. The specific goals of the MIT program are: • Pioneering theoretical research on advanced structures for high gradient acceleration, including photonic structures and metamaterial structures; evaluation of the wakefields in these advanced structures • Experimental research to demonstrate the properties of advanced structures both in low-power microwave coldmore » test and high-power, high-gradient test at megawatt power levels • Experimental research on microwave breakdown at high gradient including studies of breakdown phenomena induced by RF electric fields and RF magnetic fields; development of new diagnostics of the breakdown process • Theoretical research on the physics and engineering features of RF vacuum breakdown • Maintaining and improving the Haimson / MIT 17 GHz accelerator, the highest frequency operational accelerator in the world, a unique facility for accelerator research • Providing the Haimson / MIT 17 GHz accelerator facility as a facility for outside users • Active participation in the US DOE program of High Gradient Collaboration, including joint work with SLAC and with Los Alamos National Laboratory; participation of MIT students in research at the national laboratories • Training the next generation of Ph. D. students in the field of accelerator physics.« less
The accelerator facility of the Heidelberg Ion-Beam Therapy Centre (HIT)
NASA Astrophysics Data System (ADS)
Peters, Andreas
The following sections are included: * Introduction * Beam parameters * General layout of the HIT facility * The accelerator chain in detail * Operational aspects of a particle therapy facility * 24/7 accelerator operation at 335 days per year * Safety and regulatory aspects * Status and perspectives * References
Accelerator-Reactor Coupling for Energy Production in Advanced Nuclear Fuel Cycles
NASA Astrophysics Data System (ADS)
Heidet, Florent; Brown, Nicholas R.; Haj Tahar, Malek
This article is a review of several accelerator-reactor interface issues and nuclear fuel cycle applications of accelerator-driven subcritical systems. The systems considered here have the primary goal of energy production, but that goal is accomplished via a specific application in various proposed nuclear fuel cycles, such as breed-and-burn of fertile material or burning of transuranic material. Several basic principles are reviewed, starting from the proton beam window including the target, blanket, reactor core, and up to the fuel cycle. We focus on issues of interest, such as the impact of the energy required to run the accelerator and associated systems on the potential electricity delivered to the grid. Accelerator-driven systems feature many of the constraints and issues associated with critical reactors, with the added challenges of subcritical operation and coupling to an accelerator. Reliable accelerator operation and avoidance of beam trips are critically important. One interesting challenge is measurement of blanket subcriticality level during operation. We also review the potential benefits of accelerator-driven systems in various nuclear fuel cycle applications. Ultimately, accelerator-driven subcritical systems with the goal of transmutation of transuranic material have lower 100,000-year radioactivity than a critical fast reactor with recycling of uranium and plutonium.
Quasar feedback revealed by giant molecular outflows
NASA Astrophysics Data System (ADS)
Feruglio, C.; Maiolino, R.; Piconcelli, E.; Menci, N.; Aussel, H.; Lamastra, A.; Fiore, F.
2010-07-01
In the standard scenario for galaxy evolution young star-forming galaxies transform into red bulge-dominated spheroids, where star formation has been quenched. To explain this transformation, a strong negative feedback generated by accretion onto a central super-massive black hole is often invoked. The depletion of gas resulting from quasar-driven outflows should eventually stop star-formation across the host galaxy and lead the black hole to “suicide” by starvation. Direct observational evidence for a major quasar feedback onto the host galaxy is still missing, because outflows previously observed in quasars are generally associated with the ionized component of the gas, which only accounts for a minor fraction of the total gas content, and typically occurrs in the central regions. We used the IRAM PdB Interferometer to observe the CO(1-0) transition in Mrk 231, the closest quasar known. Thanks to the wide band we detected broad wings of the CO line, with velocities of up to 750 km s-1 and spatially resolved on the kpc scale. These broad CO wings trace a giant molecular outflow of about 700 M_⊙/year, far larger than the ongoing star-formation rate (~200 M_⊙/year) observed in the host galaxy. This wind will totally expel the cold gas reservoir in Mrk 231 in about 107 yrs, therefore halting the star-formation activity on the same timescale. The inferred kinetic energy in the molecular outflow is ~1.2 × 1044 erg/s, corresponding to a few percent of the AGN bolometric luminosity, which is very close to the fraction expected by models ascribing quasar feedback to highly supersonic shocks generated by radiatively accelerated nuclear winds. Instead, the contribution by the SNe associated with the starburst fall short by several orders of magnitude to account for the kinetic energy observed in the outflow. The direct observational evidence for quasar feedback reported here provides solid support to the scenarios ascribing the observed properties of local massive
"Homework Feedback Is…": Elementary and Middle School Teachers' Conceptions of Homework Feedback.
Cunha, Jennifer; Rosário, Pedro; Núñez, José Carlos; Nunes, Ana Rita; Moreira, Tânia; Nunes, Tânia
2018-01-01
This study explored mathematics teachers' conceptions of the homework feedback focusing on four key aspects: definition, purpose, types, and perceived impact. Forty-seven teachers from elementary and middle schools participated in six focus groups. Data were analyzed using content analysis. To enhance the trustworthiness of findings, classroom observations were used for triangulation of data. Participants conceptualized homework feedback in three directions (i.e., teachers' feedback provided to students, students' feedback provided to teachers, and homework self-feedback), being teachers' monitoring of students' learning the purpose reported by most teachers. Participants also reported the types of homework feedback more frequently used in class (e.g., checking homework completion, checking homework on the board), and their perceived impact on students. Findings provide valuable information to deepen the understanding of the homework feedback process, which may help develop new avenues for future research.
Principles of Induction Accelerators
NASA Astrophysics Data System (ADS)
Briggs*, Richard J.
The basic concepts involved in induction accelerators are introduced in this chapter. The objective is to provide a foundation for the more detailed coverage of key technology elements and specific applications in the following chapters. A wide variety of induction accelerators are discussed in the following chapters, from the high current linear electron accelerator configurations that have been the main focus of the original developments, to circular configurations like the ion synchrotrons that are the subject of more recent research. The main focus in the present chapter is on the induction module containing the magnetic core that plays the role of a transformer in coupling the pulsed power from the modulator to the charged particle beam. This is the essential common element in all these induction accelerators, and an understanding of the basic processes involved in its operation is the main objective of this chapter. (See [1] for a useful and complementary presentation of the basic principles in induction linacs.)
Method for generating a plasma wave to accelerate electrons
Umstadter, D.; Esarey, E.; Kim, J.K.
1997-06-10
The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention. 21 figs.
Method for generating a plasma wave to accelerate electrons
Umstadter, Donald; Esarey, Eric; Kim, Joon K.
1997-01-01
The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention.
Helium refrigeration systems for super-conducting accelerators
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ganni, V.
Many of the present day accelerators are based on superconducting technology which requires 4.5-K or 2-K helium refrigeration systems. These systems utilize superconducting radio frequency (SRF) cavities and/or superconducting magnets which are packaged into vacuum vessels known as cryo-modules (CM’s). Many of the present day accelerators are optimized to operate primarily at around 2-K, requiring specialized helium refrigeration systems which are cost intensive to produce and to operate. Some of the cryogenic refrigeration system design considerations for these challenging applications are discussed.
Knowledge engineering for PACES, the particle accelerator control expert system
NASA Astrophysics Data System (ADS)
Lind, P. C.; Poehlman, W. F. S.; Stark, J. W.; Cousins, T.
1992-04-01
The KN-3000 used at Defense Research Establishment Ottawa is a Van de Graaff particle accelerator employed primarily to produce monoenergetic neutrons for calibrating radiation detectors. To provide training and assistance for new operators, it was decided to develop an expert system for accelerator operation. Knowledge engineering aspects of the expert system are reviewed. Two important issues are involved: the need to encapsulate expert knowledge into the system in a form that facilitates automatic accelerator operation and to partition the system so that time-consuming inferencing is minimized in favor of faster, more algorithmic control. It is seen that accelerator control will require fast, narrowminded decision making for rapid fine tuning, but slower and broader reasoning for machine startup, shutdown, fault diagnosis, and correction. It is also important to render the knowledge base in a form conducive to operator training. A promising form of the expert system involves a hybrid system in which high level reasoning is performed on the host machine that interacts with the user, while an embedded controller employs neural networks for fast but limited adjustment of accelerator performance. This partitioning of duty facilitates a hierarchical chain of command yielding an effective mixture of speed and reasoning ability.
Sultan, Amber Shamim; Mateen Khan, Muhammad Arif
2017-07-01
Feedback is considered as a dynamic process in which information about the observed performance is used to promote the desirable behaviour and correct the negative ones. The importance of feedback is widely acknowledged, but still there seems to be inconsistency in the amount, type and timing of feedback received from the clinical faculty. No significant effort has been put forward from the educator end to empower the learners with the skills of receiving and using the feedback effectively. Some institutions conduct faculty development workshops and courses to facilitate the clinicians on how best to deliver constructive feedback to the learners. Despite of all these struggles learners are not fully satisfied with the quality of feedback received from their busy clinicians. The aim of this paper is to highlight what actually feedback is, type and structure of feedback, the essential components of a constructive feedback, benefits of providing feedback, barriers affecting the provision of timely feedback and different models used for providing feedback. The ultimate purpose of this paper is to provide sufficient information to the clinical directors that there is a need to establish a robust system for giving feedback to learners and to inform all the clinical educators with the skills required to provide constructive feedback to their learners. For the literature review, we had used the key words glossary as: Feedback, constructive feedback, barriers to feedback, principles of constructive feedback, Models of feedback, reflection, self-assessment and clinical practice etc. The data bases for the search include: Cardiff University library catalogue, Pub Med, Google Scholar, Web of Knowledge and Science direct.
Computer Simulated Visual and Tactile Feedback as an Aid to Manipulator and Vehicle Control,
1981-05-08
STATEMENT ........................ 8 Artificial Intellegence Versus Supervisory Control ....... 8 Computer Generation of Operator Feedback...operator. Artificial Intelligence Versus Supervisory Control The use of computers to aid human operators can be divided into two catagories: artificial ...operator. Artificial intelligence ( A. I. ) attempts to give the computer maximum intelligence and to replace all operator functions by the computer
Jackman, Jay M; Strober, Myra H
2003-04-01
Nobody likes performance reviews. Subordinates are terrified they'll hear nothing but criticism. Bosses think their direct reports will respond to even the mildest criticism with anger or tears. The result? Everyone keeps quiet. That's unfortunate, because most people need help figuring out how to improve their performance and advance their careers. This fear of feedback doesn't come into play just during annual reviews. At least half the executives with whom the authors have worked never ask for feedback. Many expect the worst: heated arguments, even threats of dismissal. So rather than seek feedback, people try to guess what their bosses are thinking. Fears and assumptions about feedback often manifest themselves in psychologically maladaptive behaviors such as procrastination, denial, brooding, jealousy, and self-sabotage. But there's hope, say the authors. Those who learn adaptive techniques can free themselves from destructive responses. They'll be able to deal with feedback better if they acknowledge negative emotions, reframe fear and criticism constructively, develop realistic goals, create support systems, and reward themselves for achievements along the way. Once you've begun to alter your maladaptive behaviors, you can begin seeking regular feedback from your boss. The authors take you through four steps for doing just that: self-assessment, external assessment, absorbing the feedback, and taking action toward change. Organizations profit when employees ask for feedback and deal well with criticism. Once people begin to know how they are doing relative to management's priorities, their work becomes better aligned with organizational goals. What's more, they begin to transform a feedback-averse environment into a more honest and open one, in turn improving performance throughout the organization.
Methods of Phase and Power Control in Magnetron Transmitters for Superconducting Accelerators
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kazadevich, G.; Johnson, R.; Neubauer, M.
Various methods of phase and power control in magnetron RF sources of superconducting accelerators intended for ADS-class projects were recently developed and studied with conventional 2.45 GHz, 1 kW, CW magnetrons operating in pulsed and CW regimes. Magnetron transmitters excited by a resonant (injection-locking) phasemodulated signal can provide phase and power control with the rates required for precise stabilization of phase and amplitude of the accelerating field in Superconducting RF (SRF) cavities of the intensity-frontier accelerators. An innovative technique that can significantly increase the magnetron transmitter efficiency at the widerange power control required for superconducting accelerators was developed and verifiedmore » with the 2.45 GHz magnetrons operating in CW and pulsed regimes. High efficiency magnetron transmitters of this type can significantly reduce the capital and operation costs of the ADSclass accelerator projects.« less
The problem of automation: Inappropriate feedback and interaction, not overautomation
NASA Technical Reports Server (NTRS)
Norman, Donald A.
1989-01-01
As automation increasingly takes its place in industry, especially high-risk industry, it is often blamed for causing harm and increasing the chance of human error when failures occur. It is proposed that the problem is not the presence of automation, but rather its inappropriate design. The problem is that the operations are performed appropriately under normal conditions, but there is inadequate feedback and interaction with the humans who must control the overall conduct of the task. When the situations exceed the capabilities of the automatic equipment, then the inadequate feedback leads to difficulties for the human controllers. The problem is that the automation is at an intermediate level of intelligence, powerful enough to take over control that which used to be done by people, but not powerful enough to handle all abnormalities. Moreover, its level of intelligence is insufficient to provide the continual, appropriate feedback that occurs naturally among human operators. To solve this problem, the automation should either be made less intelligent or more so, but the current level is quite inappropriate. The overall message is that it is possible to reduce error through appropriate design considerations.
Roach, Paul B; Roggin, Kevin K; Selkov, Gene; Posner, Mitchell C; Silverstein, Jonathan C
2009-01-01
We developed a convenient mechanism, Surgical Training and Assessment Tool (STAT), to accomplish detailed, continuous analysis of surgical trainees' operative abilities, and a simple method, Quality Based Surgical Training (QBST) for implementing it. Using a web-accessed computer program, attending physicians and trainees independently assessed the trainee's operative performance after every operative (training) case. Global attributes of surgical knowledge, skill, and independence were assessed as well as the key technical maneuvers of each operation. A system of hierarchical, expandable menus specific to each of hundreds of different surgical procedures allowed the assessments to be made as detailed or as general as the users felt were necessary. In addition, freehand, unscripted commentary was recorded via an optional "remarks" box feature. Finally, an independently chosen, "overall" grade scaled F through A+ concluded each assessment. Over a 31 month period, 72 different users (52 trainees, 20 attending physicians) submitted 3849 performance assessments on 2424 cases, including 132 different case types and amassing 68,260 distinct data points. The mean number of data points per trainee was 1313; the median time spent per assessment was 60 seconds. Graphic displays allowed formative review of individual cases in real time, and summative review of long term trends. Appraisals of knowledge, skill, and independence were strongly correlated with and independently predictive of the overall competency grade (model r(2) = 0.68; test of predictive significance p < 0.001 for each rating). Trainee and attending physician scores were highly correlated (> 0.7) with one another. QBST/STAT achieves detailed, continuous analysis of surgical trainees' operative abilities, and facilitates timely, specific, and thorough feedback regarding their performance in theater. QBST/STAT promotes trainee self-reflection and generation of continuous, transparent, iterative training goals.
Testing of a Loop Heat Pipe Subjective to Variable Accelerations. Part 2; Temperature Stability
NASA Technical Reports Server (NTRS)
Ku, Jentung; Ottenstein, Laura; Kaya, Taril; Rogers, Paul; Hoff, Craig
2000-01-01
The effect of accelerating forces on the performance of loop heat pipes (LHP) is of interest and importance to terrestrial and space applications. LHP's are being considered for cooling of military combat vehicles and for spinning spacecraft. In order to investigate the effect of an accelerating force on LHP operation, a miniature LHP was installed on a spin table. Variable accelerating forces were imposed on the LHP by spinning the table at different angular speeds. Several patterns of accelerating forces were applied, i.e. continuous spin at different speeds and periodic spin at different speeds and frequencies. The resulting accelerations ranged from 1.17 g's to 4.7 g's. This paper presents the second part of the experimental study, i.e. the effect of an accelerating force on the LHP operating temperature. It has been known that in stationary tests the LHP operating temperature is a function of the evaporator power and the condenser sink temperature when the compensation temperature is not actively controlled. Results of this test program indicate that any change in the accelerating force will result in a chance in the LHP operating temperature through its influence on the fluid distribution in the evaporator, condenser and compensation chamber. However, the effect is not universal, rather it is a function of other test conditions. A steady, constant acceleration may result in an increase or decrease of the operating temperature, while a periodic spin will lead to a quasi-steady operating temperature over a sufficient time interval. In addition, an accelerating force may lead to temperature hysteresis and changes in the temperature oscillation. In spite of all these effects, the LHP continued to operate without any problems in all tests.
Seeing the risks of multiple Arctic amplifying feedbacks.
NASA Astrophysics Data System (ADS)
Carter, P.
2014-12-01
There are several potentially very large sources of Arctic amplifying feedbacks that have been identified. They present a great risk to the future as they could become self and inter-reinforcing with uncontrollable knock-on, or cascading risks. This has been called a domino effect risk by Carlos Duarte. Because of already committed global warming and the millennial duration of global warming, these are highly policy relevant. These Arctic feedback processes are now all operant with emissions of carbon dioxide methane and nitrous oxide detected. The extent of the risks from these feedback sources are not obvious or easy to understand by policy makers and the public. They are recorded in the IPCC AR5 as potential tipping points, as is the irreversibility of permafrost thaw. Some of them are not accounted for in the IPCC AR5 global warming projections because of quantitative uncertainty. UNEP issued a 2012 report (Policy Implications of Thawing Permafrost) advising that by omitting carbon feedback emissions from permafrost, carbon budget calculations by err on the low side. There is the other unassessed issue of a global warming safety limit for preventing uncontrollable increasing Arctic feedback emissions. Along with our paper, we provide illustrations of the Arctic feedback sources and processes from satellite imagery and flow charts that allows for their qualitative consideration. We rely on the IPCC assessments, the 2012 paper Possible role of wetlands permafrost can methane hydrates in the methane cycle under future climate change; a review, by Fiona M. O'Connor et al., and build on the WWF 2009 Arctic Climate Feedbacks: Global Implications. The potential sources of Arctic feedback processes identified include: Arctic and Far North snow albedo decline, Arctic summer sea ice albedo decline, Greenland summer ice surface melting albedo loss, albedo decline by replacement of Arctic tundra with forest, tundra fires, Boreal forest fires, Boreal forest die
Feedback-related brain activity predicts learning from feedback in multiple-choice testing.
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.
Jin, Seung-A Annie
2010-06-01
This study gauged the effects of force feedback in the Novint Falcon haptics system on the sensory and cognitive dimensions of a virtual test-driving experience. First, in order to explore the effects of tactile stimuli with force feedback on users' sensory experience, feelings of physical presence (the extent to which virtual physical objects are experienced as actual physical objects) were measured after participants used the haptics interface. Second, to evaluate the effects of force feedback on the cognitive dimension of consumers' virtual experience, this study investigated brand personality perception. The experiment utilized the Novint Falcon haptics controller to induce immersive virtual test-driving through tactile stimuli. The author designed a two-group (haptics stimuli with force feedback versus no force feedback) comparison experiment (N = 238) by manipulating the level of force feedback. Users in the force feedback condition were exposed to tactile stimuli involving various force feedback effects (e.g., terrain effects, acceleration, and lateral forces) while test-driving a rally car. In contrast, users in the control condition test-drove the rally car using the Novint Falcon but were not given any force feedback. Results of ANOVAs indicated that (a) users exposed to force feedback felt stronger physical presence than those in the no force feedback condition, and (b) users exposed to haptics stimuli with force feedback perceived the brand personality of the car to be more rugged than those in the control condition. Managerial implications of the study for product trial in the business world are discussed.
Feedback in surgical education.
El Boghdady, Michael; Alijani, Afshin
2017-04-01
The positive effect of feedback has long been recognized in surgical education. Surgical educators convey feedback to improve the performance of the surgical trainees. We aimed to review the scientific classification and application of feedback in surgical education, and to propose possible future directions for research. A literature search was performed using Pubmed, OVID, CINAHL, Web of science, EMBASE, ERIC database and Google Scholar. The following search terms were used: 'feedback', 'feedback in medical education', 'feedback in medical training' and 'feedback in surgery'. The search was limited to articles in English. From 1157 citations, 12 books and 43 articles met the inclusion criteria and were selected for this review. Feedback comes in a variety of types and is an essential tool for learning and developing performance in surgical education. Different methods of feedback application are evolving and future work needs to concentrate on the value of each method as well as the role of new technologies in surgical education. Copyright © 2016 Royal College of Surgeons of Edinburgh (Scottish charity number SC005317) and Royal College of Surgeons in Ireland. Published by Elsevier Ltd. All rights reserved.
Chand, Manish; De'Ath, Henry D; Rasheed, Shahnawaz; Mehta, Chaitanya; Bromilow, James; Qureshi, Tahseen
2016-01-01
Laparoscopic surgery is well established in the modern management of colorectal disease. More recently, enhanced recovery after surgery (ERAS) protocols have been introduced to further promote accelerated discharge and faster recovery. However, not all patients are suitable for early discharge. The purpose of this study was to evaluate the early outcomes of patients undergoing such a regime to determine which peri-operative factors may predict safe accelerated discharge. Data were prospectively collected on consecutive patients undergoing laparoscopic colorectal surgery. All patients followed the institution's ERAS protocol and were discharged once specific criteria were fulfilled. Clinical characteristics and outcomes were compared between patients who were discharged before and after 72 h post-surgery. Thereafter, the peri-operative factors that were associated with delayed discharge were determined using a binary logistic model. Three hundred patients were included in the analysis. The most common operation was laparoscopic anterior resection (n = 123, 41%). Mean length of stay was 4.8 days (standard deviation 5.9), with 185 (62%) patients discharged within 72 h. Ten (3%) patients had a post-operative complication. Three independent predictors of delayed discharge were identified; BMI (OR 1.06, 95%CI 1.01-1.11), operation length (OR 0.99, 95%CI 0.98-0.99) and complications (OR 16.26, 95%CI 4.88-54.08). A combined approach of laparoscopic surgery and ERAS leads to reduced length of stay. This enables more than 60% of patients to be discharged within 72 h. Increased BMI, duration of operation and complications post-operatively independently predict a longer length of stay. Copyright © 2015 IJS Publishing Group Limited. Published by Elsevier Ltd. All rights reserved.
ERIC Educational Resources Information Center
Shute, Valerie J.
2008-01-01
This article reviews the corpus of research on feedback, with a focus on formative feedback--defined as information communicated to the learner that is intended to modify his or her thinking or behavior to improve learning. According to researchers, formative feedback should be nonevaluative, supportive, timely, and specific. Formative feedback is…
30 CFR 56.19062 - Maximum acceleration and deceleration.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Maximum acceleration and deceleration. 56.19062 Section 56.19062 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND... Hoisting Hoisting Procedures § 56.19062 Maximum acceleration and deceleration. Maximum normal operating...
30 CFR 57.19062 - Maximum acceleration and deceleration.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Maximum acceleration and deceleration. 57.19062 Section 57.19062 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND... Hoisting Hoisting Procedures § 57.19062 Maximum acceleration and deceleration. Maximum normal operating...
NASA Technical Reports Server (NTRS)
Parker, L. Neergaard; Zank, G. P.
2013-01-01
Successful forecasting of energetic particle events in space weather models require algorithms for correctly predicting the spectrum of ions accelerated from a background population of charged particles. We present preliminary results from a model that diffusively accelerates particles at multiple shocks. Our basic approach is related to box models in which a distribution of particles is diffusively accelerated inside the box while simultaneously experiencing decompression through adiabatic expansion and losses from the convection and diffusion of particles outside the box. We adiabatically decompress the accelerated particle distribution between each shock by either the method explored in Melrose and Pope (1993) and Pope and Melrose (1994) or by the approach set forth in Zank et al. (2000) where we solve the transport equation by a method analogous to operator splitting. The second method incorporates the additional loss terms of convection and diffusion and allows for the use of a variable time between shocks. We use a maximum injection energy (E(sub max)) appropriate for quasi-parallel and quasi-perpendicular shocks and provide a preliminary application of the diffusive acceleration of particles by multiple shocks with frequencies appropriate for solar maximum (i.e., a non-Markovian process).
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…
Payne, Velma L; Hysong, Sylvia J
2016-07-13
Audit and feedback (A&F) is a strategy that has been used in various disciplines for performance and quality improvement. There is limited research regarding medical professionals' acceptance of clinical-performance feedback and whether feedback impacts clinical practice. The objectives of our research were to (1) investigate aspects of A&F that impact physicians' acceptance of performance feedback; (2) determine actions physicians take when receiving feedback; and (3) determine if feedback impacts physicians' patient-management behavior. In this qualitative study, we employed grounded theory methods to perform a secondary analysis of semi-structured interviews with 12 VA primary care physicians. We analyzed a subset of interview questions from the primary study, which aimed to determine how providers of high, low and moderately performing VA medical centers use performance feedback to maintain and improve quality of care, and determine perceived utility of performance feedback. Based on the themes emergent from our analysis and their observed relationships, we developed a model depicting aspects of the A&F process that impact feedback acceptance and physicians' patient-management behavior. The model is comprised of three core components - Reaction, Action and Impact - and depicts elements associated with feedback recipients' reaction to feedback, action taken when feedback is received, and physicians modifying their patient-management behavior. Feedback characteristics, the environment, external locus-of-control components, core values, emotion and the assessment process induce or deter reaction, action and impact. Feedback characteristics (content and timeliness), and the procedural justice of the assessment process (unjust penalties) impact feedback acceptance. External locus-of-control elements (financial incentives, competition), the environment (patient volume, time constraints) and emotion impact patient-management behavior. Receiving feedback generated
Modeling the Acceleration of Global Surface Temperture
NASA Astrophysics Data System (ADS)
Jones, B.
2017-12-01
A mathematical projection focusing on the changing rate of acceleration of Global Surface Temperatures. Using historical trajectory and informed expert near-term prediction, it is possible to extend this further forward drawing a reference arc of acceleration. Presented here is an example of this technique based on data found in the Summary of Findings of A New Estimate of the Average Earth Surface Land Temperature Spanning 1753 to 2011 and that same team's stated prediction to 2050. With this, we can project a curve showing future acceleration: Decade (midpoint) Change in Global Land Temp Degrees C Known Slope Projected Trend 1755 0.000 1955 0.600 0.0030 2005 1.500 0.0051 2045 3.000 0.0375 2095 5.485 0.0497 2145 8.895 0.0682 2195 13.488 0.0919 Observations: Slopes are getting steeper and doing so faster in an "acceleration of the acceleration" or an "arc of acceleration". This is consistent with the non-linear accelerating feedback loops of global warming. Such projected temperatures threaten human civilization and human life. This `thumbnail' projection is consistent with the other long term predictions based on anthropogenic greenhouse gases. This projection is low when compared to those whose forecasts include greenhouse gases released from thawing permafrost and clathrate hydrates. A reference line: This curve should be considered a point of reference. In the near term and absent significant drawdown of greenhouse gases, my "bet" for this AGU session is that future temperatures will generally be above this reference curve. For example, the decade ending 2020 - more than 1.9C and the decade ending 2030 - more than 2.3C - again measured from the 1750 start point. *Caveat: The long term curve and prediction assumes that mankind does not move quickly away from high cost fossil fuels and does not invent, mobilize and take actions drawing down greenhouse gases. Those seeking a comprehensive action plan are directed to drawdown.org
Thomas Jefferson National Accelerator Facility
DOE Office of Scientific and Technical Information (OSTI.GOV)
Grames, Joseph; Higinbotham, Douglas; Montgomery, Hugh
The Thomas Jefferson National Accelerator Facility (Jefferson Lab) in Newport News, Virginia, USA, is one of ten national laboratories under the aegis of the Office of Science of the U.S. Department of Energy (DOE). It is managed and operated by Jefferson Science Associates, LLC. The primary facility at Jefferson Lab is the Continuous Electron Beam Accelerator Facility (CEBAF) as shown in an aerial photograph in Figure 1. Jefferson Lab was created in 1984 as CEBAF and started operations for physics in 1995. The accelerator uses superconducting radio-frequency (srf) techniques to generate high-quality beams of electrons with high-intensity, well-controlled polarization. Themore » technology has enabled ancillary facilities to be created. The CEBAF facility is used by an international user community of more than 1200 physicists for a program of exploration and study of nuclear, hadronic matter, the strong interaction and quantum chromodynamics. Additionally, the exceptional quality of the beams facilitates studies of the fundamental symmetries of nature, which complement those of atomic physics on the one hand and of high-energy particle physics on the other. The facility is in the midst of a project to double the energy of the facility and to enhance and expand its experimental facilities. Studies are also pursued with a Free-Electron Laser produced by an energy-recovering linear accelerator.« less
NASA Technical Reports Server (NTRS)
Hallock, Ashley K.; Polzin, Kurt A.; Kimberlin, Adam C.
2012-01-01
Operational characteristics of two separate inductive thrusters with coils of different cone angles are explored through thrust stand measurements and time-integrated, un- filtered photography. Trends in impulse bit measurements indicate that, in the present experimental configuration, the thruster with the inductive coil possessing a smaller cone angle produced larger values of thrust, in apparent contradiction to results of a previous thruster acceleration model. Areas of greater light intensity in photographs of thruster operation are assumed to qualitatively represent locations of increased current density. Light intensity is generally greater in images of the thruster with the smaller cone angle when compared to those of the thruster with the larger half cone angle for the same operating conditions. The intensity generally decreases in both thrusters for decreasing mass ow rate and capacitor voltage. The location of brightest light intensity shifts upstream for decreasing mass ow rate of propellant and downstream for decreasing applied voltage. Recognizing that there typically exists an optimum ratio of applied electric field to gas pressure with respect to breakdown efficiency, this result may indicate that the optimum ratio was not achieved uniformly over the coil face, leading to non-uniform and incomplete current sheet formation in violation of the model assumption of immediate formation where all the injected propellant is contained in a magnetically-impermeable current sheet.
Relationships among supervisor feedback environment, work-related stressors, and employee deviance.
Peng, Jei-Chen; Tseng, Mei-Man; Lee, Yin-Ling
2011-03-01
Previous research has demonstrated that the employee deviance imposes enormous costs on organizational performance and productivity. Similar research supports the positive effect of favorable supervisor feedback on employee job performance. In light of such, it is important to understand the interaction between supervisor feedback environment and employee deviant behavior to streamline organization operations. The purposes of this study were to explore how the supervisor feedback environment influences employee deviance and to examine the mediating role played by work-related stressors. Data were collected from 276 subordinate-supervisor dyads at a regional hospital in Yilan. Structural equation modeling analyses were conducted to test hypotheses. Structural equation modeling analysis results show that supervisor feedback environment negatively related to interpersonal and organizational deviance. Moreover, work-related stressors were found to partially mediate the relationship between supervisor feedback environment and employee deviance. Study findings suggest that when employees (nurses in this case) perceive an appropriate supervisor-provided feedback environment, their deviance is suppressed because of the related reduction in work-related stressors. Thus, to decrease deviant behavior, organizations may foster supervisor integration of disseminated knowledge such as (a) how to improve employees' actual performance, (b) how to effectively clarify expected performance, and (c) how to improve continuous performance feedback. If supervisors absorb this integrated feedback knowledge, they should be in a better position to enhance their own daily interactions with nurses and reduce nurses' work-related stress and, consequently, decrease deviant behavior.
ERIC Educational Resources Information Center
Stone, Douglas; David-Lang, Jenn
2017-01-01
School leaders need to be able to give and receive feedback--to give it skillfully to teachers, and to receive it skillfully from, well, everyone. Most educators agree that feedback can be necessary and helpful--yet the unending cascade of new directives governing feedback often feel like a waste of time. In this article, the authors offer…
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…
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…
Real-Time Performance Feedback for the Manual Control of Spacecraft
NASA Astrophysics Data System (ADS)
Karasinski, John Austin
Real-time performance metrics were developed to quantify workload, situational awareness, and manual task performance for use as visual feedback to pilots of aerospace vehicles. Results from prior lunar lander experiments with variable levels of automation were replicated and extended to provide insights for the development of real-time metrics. Increased levels of automation resulted in increased flight performance, lower workload, and increased situational awareness. Automated Speech Recognition (ASR) was employed to detect verbal callouts as a limited measure of subjects' situational awareness. A one-dimensional manual tracking task and simple instructor-model visual feedback scheme was developed. This feedback was indicated to the operator by changing the color of a guidance element on the primary flight display, similar to how a flight instructor points out elements of a display to a student pilot. Experiments showed that for this low-complexity task, visual feedback did not change subject performance, but did increase the subjects' measured workload. Insights gained from these experiments were applied to a Simplified Aid for EVA Rescue (SAFER) inspection task. The effects of variations of an instructor-model performance-feedback strategy on human performance in a novel SAFER inspection task were investigated. Real-time feedback was found to have a statistically significant effect of improving subject performance and decreasing workload in this complicated four degree of freedom manual control task with two secondary tasks.
Feedback Linearization in a Six Degree-of-Freedom MAG-LEV Stage
NASA Technical Reports Server (NTRS)
Ludwick, Stephen J.; Trumper, David L.; Holmes, Michael L.
1996-01-01
A six degree-of-freedom electromagnetically suspended motion control stage (the Angstrom Stage) has been designed and constructed for use in short-travel, high-resolution motion control applications. It achieves better than 0.5 nm resolution over a 100 micron range of travel. The stage consists of a single moving element (the platen) floating in an oil filled chamber. The oil is crucial to the stage's operation since it forms squeeze film dampers between the platen and the frame. Twelve electromagnetic actuators provide the forces necessary to suspend and servo the platen, and six capacitance probes measure its position relative to the frame. The system is controlled using a digital signal processing board residing in a '486 based PC. This digital controller implements a feedback linearization algorithm in real-time to account for nonlinearities in both the magnetic actuators and the fluid film dampers. The feedback linearization technique reduces a highly nonlinear plant with coupling between the degrees of freedom into one that is linear, decoupled, and setpoint independent. The key to this procedure is a detailed plant model. The operation of the feedback linearization procedure is transparent to the outer loop of the controller, and so a proportional controller is sufficient for normal operation. We envision applications of this stage in scanned probe microscopy and for integrated circuit measurement.
Teachers' Emotions and Test Feedback.
ERIC Educational Resources Information Center
Stough, Laura M.; Emmer, Edmund T.
1998-01-01
Investigates teachers thoughts about test-feedback sessions and their resulting emotions and strategies when delivering feedback to students. Explains that past experiences with feedback sessions, problem students, teachers beliefs about feedback processes, and their goals for providing feedback influence the teachers level of emotion; the…
Bing-You, Robert; Ramesh, Saradha; Hayes, Victoria; Varaklis, Kalli; Ward, Denham; Blanco, Maria
2018-01-01
Construct: Medical educators consider feedback a core component of the educational process. Effective feedback allows learners to acquire new skills, knowledge, and attitudes. Learners' perceptions of feedback are an important aspect to assess with valid methods in order to improve the feedback skills of educators and the feedback culture. Although guidelines for delivering effective feedback have existed for several decades, medical students and residents often indicate that they receive little feedback. A recent scoping review on feedback in medical education did not reveal any validity evidence on instruments to assess learner's perceptions of feedback. The purpose of our study was to gather validity evidence on two novel FEEDME (Feedback in Medical Education) instruments to assess medical students' and residents' perceptions of the feedback that they receive. After the authors developed an initial instrument with 54 items, cognitive interviews with medical students and residents suggested that 2 separate instruments were needed, one focused on the feedback culture (FEEDME-Culture) and the other on the provider of feedback (FEEDME-Provider). A Delphi study with 17 medical education experts and faculty members assessed content validity. The response process was explored involving 31 medical students and residents at 2 academic institutions. Exploratory factor analysis and reliability analyses were performed on completed instruments. Two Delphi consultation rounds refined the wording of items and eliminated several items. Learners found both instruments easy and quick to answer; it took them less than 5 minutes to complete. Learners preferred an electronic format of the instruments over paper. Factor analysis revealed a two- and three-factor solution for the FEEDME-Culture and FEEDME-Provider instruments, respectively. Cronbach's alpha was greater than 0.80 for all factors. Items on both instruments were moderately to highly correlated (range, r = .3-.7). Our
Monitoring Digital Closed-Loop Feedback Systems
NASA Technical Reports Server (NTRS)
Katz, Richard; Kleyner, Igor
2011-01-01
A technique of monitoring digital closed-loop feedback systems has been conceived. The basic idea is to obtain information on the performances of closed-loop feedback circuits in such systems to aid in the determination of the functionality and integrity of the circuits and of performance margins. The need for this technique arises as follows: Some modern digital systems include feedback circuits that enable other circuits to perform with precision and are tolerant of changes in environment and the device s parameters. For example, in a precision timing circuit, it is desirable to make the circuit insensitive to variability as a result of the manufacture of circuit components and to the effects of temperature, voltage, radiation, and aging. However, such a design can also result in masking the indications of damaged and/or deteriorating components. The present technique incorporates test circuitry and associated engineering-telemetry circuitry into an embedded system to monitor the closed-loop feedback circuits, using spare gates that are often available in field programmable gate arrays (FPGAs). This technique enables a test engineer to determine the amount of performance margin in the system, detect out of family circuit performance, and determine one or more trend(s) in the performance of the system. In one system to which the technique has been applied, an ultra-stable oscillator is used as a reference for internal adjustment of 12 time-to-digital converters (TDCs). The feedback circuit produces a pulse-width-modulated signal that is fed as a control input into an amplifier, which controls the circuit s operating voltage. If the circuit s gates are determined to be operating too slowly or rapidly when their timing is compared with that of the reference signal, then the pulse width increases or decreases, respectively, thereby commanding the amplifier to increase or reduce, respectively, its output level, and "adjust" the speed of the circuits. The nominal
NASA Astrophysics Data System (ADS)
Choi, Seung-Hyun; Kim, Soomin; Kim, Pyunghwa; Park, Jinhyuk; Choi, Seung-Bok
2015-06-01
In this study, we developed a novel four-degrees-of-freedom haptic master using controllable magnetorheological (MR) fluid. We also integrated the haptic master with a vision device with image processing for robot-assisted minimally invasive surgery (RMIS). The proposed master can be used in RMIS as a haptic interface to provide the surgeon with a sense of touch by using both kinetic and kinesthetic information. The slave robot, which is manipulated with a proportional-integrative-derivative controller, uses a force sensor to obtain the desired forces from tissue contact, and these desired repulsive forces are then embodied through the MR haptic master. To verify the effectiveness of the haptic master, the desired force and actual force are compared in the time domain. In addition, a visual feedback system is implemented in the RMIS experiment to distinguish between the tumor and organ more clearly and provide better visibility to the operator. The hue-saturation-value color space is adopted for the image processing since it is often more intuitive than other color spaces. The image processing and haptic feedback are realized on surgery performance. In this work, tumor-cutting experiments are conducted under four different operating conditions: haptic feedback on, haptic feedback off, image processing on, and image processing off. The experimental realization shows that the performance index, which is a function of pixels, is different in the four operating conditions.
Developments and applications of accelerator system at the Wakasa Wan Energy Research Center
NASA Astrophysics Data System (ADS)
Hatori, S.; Kurita, T.; Hayashi, Y.; Yamada, M.; Yamada, H.; Mori, J.; Hamachi, H.; Kimura, S.; Shimoda, T.; Hiroto, M.; Hashimoto, T.; Shimada, M.; Yamamoto, H.; Ohtani, N.; Yasuda, K.; Ishigami, R.; Sasase, M.; Ito, Y.; Hatashita, M.; Takagi, K.; Kume, K.; Fukuda, S.; Yokohama, N.; Kagiya, G.; Fukumoto, S.; Kondo, M.
2005-12-01
At the Wakasa Wan Energy Research Center (WERC), an accelerator system with a 5 MV tandem accelerator and a 200 MeV proton synchrotron is used for ion beam analyses and irradiation experiments. The study of cancer therapy with a proton beam is also performed. Therefore, the stable operation and efficient sharing of beam time of the system are required, based on the treatment standard. Recent developments and the operation status of the system put stress on the tandem accelerator operation, magnifying the problems.
An Expert System For Tuning Particle-Beam Accelerators
NASA Astrophysics Data System (ADS)
Lager, Darrel L.; Brand, Hal R.; Maurer, William J.; Searfus, Robert M.; Hernandez, Jose E.
1989-03-01
We have developed a proof-of-concept prototype of an expert system for tuning particle beam accelerators. It is designed to function as an intelligent assistant for an operator. In its present form it implements the strategies and reasoning followed by the operator for steering through the beam transport section of the Advanced Test Accelerator at Lawrence Livermore Laboratory's Site 300. The system is implemented in the language LISP using the Artificial Intelligence concepts of frames, daemons, and a representation we developed called a Monitored Decision Script.
Feedback and efficient behavior
2017-01-01
Feedback is an effective tool for promoting efficient behavior: it enhances individuals’ awareness of choice consequences in complex settings. Our study aims to isolate the mechanisms underlying the effects of feedback on achieving efficient behavior in a controlled environment. We design a laboratory experiment in which individuals are not aware of the consequences of different alternatives and, thus, cannot easily identify the efficient ones. We introduce feedback as a mechanism to enhance the awareness of consequences and to stimulate exploration and search for efficient alternatives. We assess the efficacy of three different types of intervention: provision of social information, manipulation of the frequency, and framing of feedback. We find that feedback is most effective when it is framed in terms of losses, that it reduces efficiency when it includes information about inefficient peers’ behavior, and that a lower frequency of feedback does not disrupt efficiency. By quantifying the effect of different types of feedback, our study suggests useful insights for policymakers. PMID:28430787
Group Feedback for Continuous Learning
ERIC Educational Resources Information Center
London, Manuel; Sessa, Valerie I.
2006-01-01
This article explores relationships between feedback, group learning, and performance. It considers how feedback to individuals and the group as a whole supports continuous group learning. Feedback source, purpose, clarity, and valence may affect perceptions, processing, and outcomes of feedback. How feedback is processed and used may be…
Frequency-Offset Cartesian Feedback Based on Polyphase Difference Amplifiers
Zanchi, Marta G.; Pauly, John M.; Scott, Greig C.
2010-01-01
A modified Cartesian feedback method called “frequency-offset Cartesian feedback” and based on polyphase difference amplifiers is described that significantly reduces the problems associated with quadrature errors and DC-offsets in classic Cartesian feedback power amplifier control systems. In this method, the reference input and feedback signals are down-converted and compared at a low intermediate frequency (IF) instead of at DC. The polyphase difference amplifiers create a complex control bandwidth centered at this low IF, which is typically offset from DC by 200–1500 kHz. Consequently, the loop gain peak does not overlap DC where voltage offsets, drift, and local oscillator leakage create errors. Moreover, quadrature mismatch errors are significantly attenuated in the control bandwidth. Since the polyphase amplifiers selectively amplify the complex signals characterized by a +90° phase relationship representing positive frequency signals, the control system operates somewhat like single sideband (SSB) modulation. However, the approach still allows the same modulation bandwidth control as classic Cartesian feedback. In this paper, the behavior of the polyphase difference amplifier is described through both the results of simulations, based on a theoretical analysis of their architecture, and experiments. We then describe our first printed circuit board prototype of a frequency-offset Cartesian feedback transmitter and its performance in open and closed loop configuration. This approach should be especially useful in magnetic resonance imaging transmit array systems. PMID:20814450
An introduction to the physics of high energy accelerators
DOE Office of Scientific and Technical Information (OSTI.GOV)
Edwards, D.A.; Syphers, J.J.
1993-01-01
This book is an outgrowth of a course given by the authors at various universities and particle accelerator schools. It starts from the basic physics principles governing particle motion inside an accelerator, and leads to a full description of the complicated phenomena and analytical tools encountered in the design and operation of a working accelerator. The book covers acceleration and longitudinal beam dynamics, transverse motion and nonlinear perturbations, intensity dependent effects, emittance preservation methods and synchrotron radiation. These subjects encompass the core concerns of a high energy synchrotron. The authors apparently do not assume the reader has much previous knowledgemore » about accelerator physics. Hence, they take great care to introduce the physical phenomena encountered and the concepts used to describe them. The mathematical formulae and derivations are deliberately kept at a level suitable for beginners. After mastering this course, any interested reader will not find it difficult to follow subjects of more current interests. Useful homework problems are provided at the end of each chapter. Many of the problems are based on actual activities associated with the design and operation of existing accelerators.« less
Benkert, Thomas; Tian, Ye; Huang, Chenchan; DiBella, Edward V R; Chandarana, Hersh; Feng, Li
2018-07-01
Golden-angle radial sparse parallel (GRASP) MRI reconstruction requires gridding and regridding to transform data between radial and Cartesian k-space. These operations are repeatedly performed in each iteration, which makes the reconstruction computationally demanding. This work aimed to accelerate GRASP reconstruction using self-calibrating GRAPPA operator gridding (GROG) and to validate its performance in clinical imaging. GROG is an alternative gridding approach based on parallel imaging, in which k-space data acquired on a non-Cartesian grid are shifted onto a Cartesian k-space grid using information from multicoil arrays. For iterative non-Cartesian image reconstruction, GROG is performed only once as a preprocessing step. Therefore, the subsequent iterative reconstruction can be performed directly in Cartesian space, which significantly reduces computational burden. Here, a framework combining GROG with GRASP (GROG-GRASP) is first optimized and then compared with standard GRASP reconstruction in 22 prostate patients. GROG-GRASP achieved approximately 4.2-fold reduction in reconstruction time compared with GRASP (∼333 min versus ∼78 min) while maintaining image quality (structural similarity index ≈ 0.97 and root mean square error ≈ 0.007). Visual image quality assessment by two experienced radiologists did not show significant differences between the two reconstruction schemes. With a graphics processing unit implementation, image reconstruction time can be further reduced to approximately 14 min. The GRASP reconstruction can be substantially accelerated using GROG. This framework is promising toward broader clinical application of GRASP and other iterative non-Cartesian reconstruction methods. Magn Reson Med 80:286-293, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.
Neurotechnology to accelerate learning: during marksmanship training.
Behneman, Adrienne; Berka, Chris; Stevens, Ronald; Vila, Bryan; Tan, Veasna; Galloway, Trysha; Johnson, Robin; Raphael, Giby
2012-01-01
This article explores the psychophysiological metrics during expert and novice performances in marksmanship, combat deadly force judgment and decision making (DFJDM), and interactions of teams. Electroencephalography (EEG) and electrocardiography (ECG) are used to characterize the psychophysiological profiles within all categories. Closed-loop biofeedback was administered to accelerate learning during marksmanship training in which the results show a difference in groups that received feedback compared with the control. During known distance marksmanship and DFJDM scenarios, experts show superior ability to control physiology to meet the demands of the task. Expertise in teaming scenarios is characterized by higher levels of cohesiveness than those seen in novices.
Preliminary tests of the electrostatic plasma accelerator
NASA Technical Reports Server (NTRS)
Aston, G.; Acker, T.
1990-01-01
This report describes the results of a program to verify an electrostatic plasma acceleration concept and to identify those parameters most important in optimizing an Electrostatic Plasma Accelerator (EPA) thruster based upon this thrust mechanism. Preliminary performance measurements of thrust, specific impulse and efficiency were obtained using a unique plasma exhaust momentum probe. Reliable EPA thruster operation was achieved using one power supply.
SABRE, a 10-MV linear induction accelerator
DOE Office of Scientific and Technical Information (OSTI.GOV)
Corely, J.P.; Alexander, J.A.; Pankuch, P.J.
SABRE (Sandia Accelerator and Beam Research Experiment) is a 10-MV, 250-kA, 40-ns linear induction accelerator. It was designed to be used in positive polarity output. Positive polarity accelerators are important for application to Sandia's ICF (Inertial Confinement Fusion) and LMF (Laboratory Microfusion Facility) program efforts. SABRE was built to allow a more detailed study of pulsed power issues associated with positive polarity output machines. MITL (Magnetically Insulated Transmission Line) voltage adder efficiency, extraction ion diode development, and ion beam transport and focusing. The SABRE design allows the system to operate in either positive polarity output for ion extraction applications ormore » negative polarity output for more conventional electron beam loads. Details of the design of SABRE and the results of initial machine performance in negative polarity operation are presented in this paper. 13 refs., 12 figs., 1 tab.« less
Beam transport results on the multi-beam MABE accelerator
DOE Office of Scientific and Technical Information (OSTI.GOV)
Coleman, P.D.; Alexander, J.A.; Hasti, D.E.
1985-10-01
MABE is a multistage, electron beam linear accelerator. The accelerator has been operated in single beam (60 kA, 7 Mev) and multiple beam configurations. This paper deals with the multiple beam configuration in which typically nine approx. = 25 kA injected beams are transported through three accelerating gaps. Experimental results from the machine are discussed, including problems encountered and proposed solutions to those problems.
Climate-society feedbacks and the avoidance of dangerous climate change
NASA Astrophysics Data System (ADS)
Jarvis, A. J.; Leedal, D. T.; Hewitt, C. N.
2012-09-01
The growth in anthropogenic CO2 emissions experienced since the onset of the Industrial Revolution is the most important disturbance operating on the Earth's climate system. To avoid dangerous climate change, future greenhouse-gas emissions will have to deviate from business-as-usual trajectories. This implies that feedback links need to exist between climate change and societal actions. Here, we show that, consciously or otherwise, these feedbacks can be represented by linking global mean temperature change to the growth dynamics of CO2 emissions. We show that the global growth of new renewable sources of energy post-1990 represents a climate-society feedback of ~0.25%yr-1 per degree increase in global mean temperature. We also show that to fulfil the outcomes negotiated in Durban in 2011, society will have to become ~ 50 times more responsive to global mean temperature change than it has been since 1990. If global energy use continues to grow as it has done historically then this would result in amplification of the long-term endogenous rate of decarbonization from -0.6%yr-1 to ~-13%yr-1. It is apparent that modest levels of feedback sensitivity pay large dividends in avoiding climate change but that the marginal return on this effort diminishes rapidly as the required feedback strength increases.
Iterative algorithms for computing the feedback Nash equilibrium point for positive systems
NASA Astrophysics Data System (ADS)
Ivanov, I.; Imsland, Lars; Bogdanova, B.
2017-03-01
The paper studies N-player linear quadratic differential games on an infinite time horizon with deterministic feedback information structure. It introduces two iterative methods (the Newton method as well as its accelerated modification) in order to compute the stabilising solution of a set of generalised algebraic Riccati equations. The latter is related to the Nash equilibrium point of the considered game model. Moreover, we derive the sufficient conditions for convergence of the proposed methods. Finally, we discuss two numerical examples so as to illustrate the performance of both of the algorithms.
Feedbacks Between Topographic Stress and Drainage Basin Evolution
NASA Astrophysics Data System (ADS)
Perron, J.; Martel, S. J.; Singha, K.; Slim, M. I.
2013-12-01
Theoretical calculations imply that stresses produced by gravity acting on topography may be large enough in some scenarios to fracture rock. Predicted stress fields beneath ridges and valleys can differ dramatically, which has led several authors to hypothesize feedbacks between topographic stress, rock fracture and landscape evolution. However, there have been few attempts to explore these feedbacks. We use a coupled model to identify possible feedbacks between topographic stress and drainage basin evolution. The domain is a cross-section of a valley consisting of a bedrock channel and adjacent soil-mantled hillslopes. The bedrock surface evolves due to channel incision, soil production, and rock uplift, and soil thickness evolves due to soil production and transport. Plane stresses at and below the bedrock surface are calculated with a boundary element method that accounts for both ambient tectonic stress and topographic stress. We assume that the stress field experienced by rock as it is exhumed influences the likelihood that it will develop fractures, which make the rock more susceptible to weathering, disaggregation and erosion. A measure of susceptibility to shear fracture, the most likely failure mode under regional compression, serves as a proxy for rock damage. We couple the landscape evolution model to the stress model by assuming that rock damage accelerates the rates of soil production and channel incision, with two endmember cases: rates scale with the magnitude of the damage proxy at the bedrock surface, or with cumulative damage acquired during rock exhumation. The stress-induced variations in soil production and channel incision alter the soil thickness and topography, which in turn alter the stress field. Comparing model simulations with and without these feedbacks, we note several predicted consequences of topographic stress for drainage basin evolution. Rock damage is typically focused at or near the foot of hillslopes, which creates thicker
Use of visual CO2 feedback as a retrofit solution for improving classroom air quality.
Wargocki, P; Da Silva, N A F
2015-02-01
Carbon dioxide (CO2 ) sensors that provide a visual indication were installed in classrooms during normal school operation. During 2-week periods, teachers and students were instructed to open the windows in response to the visual CO2 feedback in 1 week and open them, as they would normally do, without visual feedback, in the other week. In the heating season, two pairs of classrooms were monitored, one pair naturally and the other pair mechanically ventilated. In the cooling season, two pairs of naturally ventilated classrooms were monitored, one pair with split cooling in operation and the other pair with no cooling. Classrooms were matched by grade. Providing visual CO2 feedback reduced CO2 levels, as more windows were opened in this condition. This increased energy use for heating and reduced the cooling requirement in summertime. Split cooling reduced the frequency of window opening only when no visual CO2 feedback was present. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Peterburs, Jutta; Sandrock, Carolin; Miltner, Wolfgang H R; Straube, Thomas
2016-06-01
It is as yet unknown if behavioral and neural correlates of performance monitoring in socially anxious individuals are affected by whether feedback is provided by a person or a computer. This fMRI study investigated modulation of feedback processing by feedback source (person vs. computer) in participants with high (HSA) (N=16) and low social anxiety (LSA) (N=16). Subjects performed a choice task in which they were informed that they would receive positive or negative feedback from a person or the computer. Subjective ratings indicated increased arousal and anxiety in HSA versus LSA, most pronounced for social and negative feedback. FMRI analyses yielded hyperactivation in ventral medial prefrontal cortex (vmPFC)/anterior cingulate cortex (ACC) and insula for social relative to computer feedback, and in mPFC/ventral ACC for positive relative to negative feedback in HSA as compared to LSA. These activation patterns are consistent with increased interoception and self-referential processing in social anxiety, especially during processing of positive feedback. Increased ACC activation in HSA to positive feedback may link to unexpectedness of (social) praise as posited in social anxiety disorder (SAD) psychopathology. Activation in rostral ACC showed a reversed pattern, with decreased activation to positive feedback in HSA, possibly indicating altered action values depending on feedback source and valence. The present findings corroborate a crucial role of mPFC for performance monitoring in social anxiety. Copyright © 2016 Elsevier Inc. All rights reserved.
Nottingham, Sara; Henning, Jolene
2014-01-01
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). To characterize the feedback provided by ACIs to ATSs during clinical education experiences. Qualitative study. 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. A total of 4 ACIs with various experience levels and 4 second-year ATSs. 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. 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. 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.
NASA Astrophysics Data System (ADS)
Kim, V. P.
2017-04-01
The long-term experience in controlling the electric field distribution in the discharge gaps of plasma accelerators and thrusters with closed electron drift and the key ideas determining the concepts of these devices and tendencies of their development are analyzed. It is shown that an electrostatic mechanism of ion acceleration in plasma by an uncompensated space charge of the cloud of magnetized electrons "kept" to the magnetic field takes place in the acceleration zones and that the electric field distribution can be controlled by varying the magnetic field in the discharge gap. The role played by the space charge makes the mechanism of ion acceleration in this type of thrusters is fundamentally different from the acceleration mechanism operating in purely electrostatic thrusters.
Accelerator Reactor Coupling for Energy Production in Advanced Nuclear Fuel Cycles
Brown, Nicholas R.; Heidet, Florent; Haj Tahar, Malek
2016-01-01
This article is a review of several accelerator–reactor interface issues and nuclear fuel cycle applications of acceleratordriven subcritical systems. The systems considered here have the primary goal of energy production, but that goal is accomplished via a specific application in various proposed nuclear fuel cycles, such as breed-and-burn of fertile material or burning of transuranic material. Several basic principles are reviewed, starting from the proton beam window including the target, blanket, reactor core, and up to the fuel cycle. We focus on issues of interest, such as the impact of the energy required to run the accelerator and associated systemsmore » on the potential electricity delivered to the grid. Accelerator-driven systems feature many of the constraints and issues associated with critical reactors, with the added challenges of subcritical operation and coupling to an accelerator. Reliable accelerator operation and avoidance of beam trips are critically important. One interesting challenge is measurement of blanket subcriticality level during operation. We also review the potential benefits of accelerator-driven systems in various nuclear fuel cycle applications. Ultimately, accelerator-driven subcritical systems with the goal of transmutation of transuranic material have lower 100,000-year radioactivity than a critical fast reactor with recycling of uranium and plutonium.« less
Virtual reality cerebral aneurysm clipping simulation with real-time haptic feedback.
Alaraj, Ali; Luciano, Cristian J; Bailey, Daniel P; Elsenousi, Abdussalam; Roitberg, Ben Z; Bernardo, Antonio; Banerjee, P Pat; Charbel, Fady T
2015-03-01
With the decrease in the number of cerebral aneurysms treated surgically and the increase of complexity of those treated surgically, there is a need for simulation-based tools to teach future neurosurgeons the operative techniques of aneurysm clipping. To develop and evaluate the usefulness of a new haptic-based virtual reality simulator in the training of neurosurgical residents. A real-time sensory haptic feedback virtual reality aneurysm clipping simulator was developed using the ImmersiveTouch platform. A prototype middle cerebral artery aneurysm simulation was created from a computed tomographic angiogram. Aneurysm and vessel volume deformation and haptic feedback are provided in a 3-dimensional immersive virtual reality environment. Intraoperative aneurysm rupture was also simulated. Seventeen neurosurgery residents from 3 residency programs tested the simulator and provided feedback on its usefulness and resemblance to real aneurysm clipping surgery. Residents thought that the simulation would be useful in preparing for real-life surgery. About two-thirds of the residents thought that the 3-dimensional immersive anatomic details provided a close resemblance to real operative anatomy and accurate guidance for deciding surgical approaches. They thought the simulation was useful for preoperative surgical rehearsal and neurosurgical training. A third of the residents thought that the technology in its current form provided realistic haptic feedback for aneurysm surgery. Neurosurgical residents thought that the novel immersive VR simulator is helpful in their training, especially because they do not get a chance to perform aneurysm clippings until late in their residency programs.
Appearance feedback in intimate relationships: the role of self-verification and self-enhancement.
Brown, Jennifer N; Stukas, Arthur A; Evans, Lynette
2013-01-01
To better understand how body image operates within the context of intimate relationships, we investigated women's responses to appearance feedback from an intimate partner. Participants (N=192) imagined receiving feedback from their partner that was either consistent with their own appearance self-view (i.e., self-verifying), more positive (i.e., self-enhancing), or less positive (i.e., devaluing), and then provided their affective and cognitive reactions. As expected, women's perceptions of their own appearance moderated their reactions. Women with more negative self-views felt happier with enhancing feedback, but thought that it meant their partner understood them less well. They also felt less happy when they received verifying feedback, but felt more understood by their partners. Thus, women with body image dissatisfaction may find themselves stuck in the "cognitive-affective crossfire" reacting ambivalently whether their partner enhances their appearance or confirms their negative self-views. Further examination of partners' actual feedback is needed. Copyright © 2012 Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Liu, Shuai; Huang, Yizhi; Guo, Haishan; Lin, Tianyu; Huang, Dong; Yang, Lanjun
2018-05-01
The axial characteristics of a current sheet in a parallel-plate electromagnetic plasma accelerator operated in gas-prefilled mode are reported. The accelerator is powered by a fourteen stage pulse forming network. The capacitor and inductor in each stage are 1.5 μF and 300 nH, respectively, and yield a damped oscillation square wave of current with a pulse width of 20.6 μs. Magnetic probes and photodiodes are placed at various axial positions to measure the behavior of the current sheet. Both magnetic probe and photodiode signals reveal a secondary breakdown when the current reverses the direction. An increase in the discharge current amplitude and a decrease in pressure lead to a decrease in the current shedding factor. The current sheet velocity and thickness are nearly constant during the run-down phase under the first half-period of the current. The current sheet thicknesses are typically in the range of 25 mm to 40 mm. The current sheet velocities are in the range of 10 km/s to 45 km/s when the discharge current is between 10 kA and 55 kA and the gas prefill pressure is between 30 Pa and 800 Pa. The experimental velocities are about 75% to 90% of the theoretical velocities calculated with the current shedding factor. One reason for this could be that the idealized snowplow analysis model ignores the surface drag force.
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…
Factorization and the synthesis of optimal feedback kernels for differential-delay systems
NASA Technical Reports Server (NTRS)
Milman, Mark M.; Scheid, Robert E.
1987-01-01
A combination of ideas from the theories of operator Riccati equations and Volterra factorizations leads to the derivation of a novel, relatively simple set of hyperbolic equations which characterize the optimal feedback kernel for the finite-time regulator problem for autonomous differential-delay systems. Analysis of these equations elucidates the underlying structure of the feedback kernel and leads to the development of fast and accurate numerical methods for its computation. Unlike traditional formulations based on the operator Riccati equation, the gain is characterized by means of classical solutions of the derived set of equations. This leads to the development of approximation schemes which are analogous to what has been accomplished for systems of ordinary differential equations with given initial conditions.
Dissemination and support of ARGUS for accelerator applications
DOE Office of Scientific and Technical Information (OSTI.GOV)
Not Available
The ARGUS code is a three-dimensional code system for simulating for interactions between charged particles, electric and magnetic fields, and complex structure. It is a system of modules that share common utilities for grid and structure input, data handling, memory management, diagnostics, and other specialized functions. The code includes the fields due to the space charge and current density of the particles to achieve a self-consistent treatment of the particle dynamics. The physic modules in ARGUS include three-dimensional field solvers for electrostatics and electromagnetics, a three-dimensional electromagnetic frequency-domain module, a full particle-in-cell (PIC) simulation module, and a steady-state PIC model.more » These are described in the Appendix to this report. This project has a primary mission of developing the capabilities of ARGUS in accelerator modeling of release to the accelerator design community. Five major activities are being pursued in parallel during the first year of the project. To improve the code and/or add new modules that provide capabilities needed for accelerator design. To produce a User's Guide that documents the use of the code for all users. To release the code and the User's Guide to accelerator laboratories for their own use, and to obtain feed-back from the. To build an interactive user interface for setting up ARGUS calculations. To explore the use of ARGUS on high-power workstation platforms.« less
A Novel Permanent Magnetic Angular Acceleration Sensor
Zhao, Hao; Feng, Hao
2015-01-01
Angular acceleration is an important parameter for status monitoring and fault diagnosis of rotary machinery. Therefore, we developed a novel permanent magnetic angular acceleration sensor, which is without rotation angle limitations and could directly measure the instantaneous angular acceleration of the rotating system. The sensor rotor only needs to be coaxially connected with the rotating system, which enables convenient sensor installation. For the cup structure of the sensor rotor, it has a relatively small rotational inertia. Due to the unique mechanical structure of the sensor, the output signal of the sensor can be directed without a slip ring, which avoids signal weakening effect. In this paper, the operating principle of the sensor is described, and simulated using finite element method. The sensitivity of the sensor is calibrated by torsional pendulum and angle sensor, yielding an experimental result of about 0.88 mV/(rad·s−2). Finally, the angular acceleration of the actual rotating system has been tested, using both a single-phase asynchronous motor and a step motor. Experimental result confirms the operating principle of the sensor and indicates that the sensor has good practicability. PMID:26151217
Dijksterhuis, Chris; Lewis-Evans, Ben; Jelijs, Bart; de Waard, Dick; Brookhuis, Karel; Tucha, Oliver
2015-02-01
Pay-As-You-Drive (PAYD) insurance links an individual's driving behaviour to the insurance fee that they pay, making car insurance more actuarially accurate. The best known PAYD insurance format is purely mileage based and is estimated to reduce accidents by about 15% (Litman, 2011). However, these benefits could be further enhanced by incorporating a wider range of driving behaviours, such as lateral and longitudinal accelerations and speeding behaviour, thereby stimulating not only a safe but also an eco-friendly driving style. Currently, feedback on rewards and driver behaviour is mostly provided through a web-based interface, which is presented temporally separated from driving. However, providing immediate feedback within the vehicle itself could elicit more effect. To investigate this hypothesis, two groups of 20 participants drove with a behavioural based PAYD system in a driving simulator and were provided with either delayed feedback through a website, or immediate feedback through an in-car interface, allowing them to earn up to €6 extra. To be clear, every participant in the web group did actually view their feedback during the one week between sessions. Results indicate clear driving behaviour improvements for both PAYD groups as compared to baseline rides and an equal sized control group. After both PAYD groups had received feedback, the initial advantage of the in-car group was reduced substantially. Taken together with usability ratings and driving behaviours in specific situations these results show a moderate advantage of using immediate in-car feedback. However, the study also showed that under conditions of feedback certainty, the effectiveness of delayed feedback approaches that of immediate feedback as compared to a naïve control group. Copyright © 2014 Elsevier Ltd. All rights reserved.
Huang, Susie Y; Witzel, Thomas; Wald, Lawrence L
2008-11-01
Control of the longitudinal magnetization in fast gradient-echo (GRE) sequences is an important factor in enabling the high efficiency of balanced steady-state free precession (bSSFP) sequences. We introduce a new method for accelerating the return of the longitudinal magnetization to the +z-axis that is independent of externally applied RF pulses and shows improved off-resonance performance. The accelerated radiation damping for increased spin equilibrium (ARISE) method uses an external feedback circuit to strengthen the radiation damping (RD) field. The enhanced RD field rotates the magnetization back to the +z-axis at a rate faster than T(1) relaxation. The method is characterized in GRE phantom imaging at 3T as a function of feedback gain, phase, and duration, and compared with results from numerical simulations of the Bloch equations incorporating RD. A short period of feedback (10 ms) during a refocused interval of a crushed GRE sequence allowed greater than 99% recovery of the longitudinal magnetization when very little T(2) relaxation had time to occur. An appropriate application might be to improve navigated sequences. Unlike conventional flip-back schemes, the ARISE "flip-back" is generated by the spins themselves, thereby offering a potentially useful building block for enhancing GRE sequences.
Earth's Most Powerful Natural Particle Accelerator
NASA Technical Reports Server (NTRS)
Rowland, Doug
2012-01-01
Thunderstorms launch antimatter, gamma rays, and highly energetic electrons and neutrons to the edge of space. This witches' brew of radiation is generated at the edge of the stratopause, by the strong electric fields associated with lightning discharges. In less than a quarter millisecond, an explosive feedback process takes an initial seed population of electrons, perhaps produced by cosmic rays from dying stars, and amplifies them a billion billion-fold in the rarefied air over high altitude thunderheads. The electrons generate gamma radiation as they travel through the stratosphere and lower mesosphere, momentarily brighter and of harder spectrum than cosmic gamma ray bursts. These electrons ultimately are absorbed by the atmosphere, but the gamma rays continue on, into the upper reaches of the atmosphere, where they in turn generate a new population of electrons, positrons, and energetic neutrons. These secondary electrons and positrons move along the magnetic field, and can reach near-earth space, streaming through the inner radiation belts, and possibly contributing to the trapped populations there. First postulated by Wilson in 1925, and serendipitously discovered by the Compton Gamma Ray Observatory in 1994 [Fishman et al.], these events, known as "Terrestrial Gamma ray Flashes" (TGFs), represent the most intense episodes of particle acceleration on or near the Earth, resulting in electrons with energies up to 100 MeV. Recent observations by the RHESSI [Smith et al., 2004], Fermi [Briggs et al., 2010], and AGILE [Tavani et al., 2011] satellites, and theoretical and computational modeling, have suggested that the relativistic runaway electron avalanche (RREA) mechanism [Gurevich, 1992], and important modifications, such as the relativistic feedback discharge (RFD) model [Dwyer 2012] can best explain the observations at present. In these models, strong thunderstorm electric fields drive seed electrons, generated from cosmic ray interactions, into a runaway
Self-shielded electron linear accelerators designed for radiation technologies
NASA Astrophysics Data System (ADS)
Belugin, V. M.; Rozanov, N. E.; Pirozhenko, V. M.
2009-09-01
This paper describes self-shielded high-intensity electron linear accelerators designed for radiation technologies. The specific property of the accelerators is that they do not apply an external magnetic field; acceleration and focusing of electron beams are performed by radio-frequency fields in the accelerating structures. The main characteristics of the accelerators are high current and beam power, but also reliable operation and a long service life. To obtain these characteristics, a number of problems have been solved, including a particular optimization of the accelerator components and the application of a variety of specific means. The paper describes features of the electron beam dynamics, accelerating structure, and radio-frequency power supply. Several compact self-shielded accelerators for radiation sterilization and x-ray cargo inspection have been created. The introduced methods made it possible to obtain a high intensity of the electron beam and good performance of the accelerators.
Wang, Mo; Burlacu, Gabriela; Truxillo, Donald; James, Keith; Yao, Xiang
2015-07-01
Organizations worldwide are currently experiencing shifts in the age composition of their workforces. The workforce is aging and becoming increasingly age-diverse, suggesting that organizational researchers and practitioners need to better understand how age differences may manifest in the workplace and the implications for human resource practice. Integrating socioemotional selectivity theory with the performance feedback literature and using a time-lagged design, the current study examined age differences in moderating the relationships between the characteristics of performance feedback and employee reactions to the feedback event. The results suggest that older workers had higher levels of feedback orientation on social awareness, but lower levels of feedback orientation on utility than younger workers. Furthermore, the positive associations between favorability of feedback and feedback delivery and feedback reactions were stronger for older workers than for younger workers, whereas the positive association between feedback quality and feedback reactions was stronger for younger workers than for older workers. Finally, the current study revealed that age-related differences in employee feedback orientation could explain the different patterns of relationships between feedback characteristics and feedback reactions across older and younger workers. These findings have both theoretical and practical implications for building theory about workplace aging and improving ways that performance feedback is managed across employees from diverse age groups. (c) 2015 APA, all rights reserved).
“Homework Feedback Is…”: Elementary and Middle School Teachers’ Conceptions of Homework Feedback
Cunha, Jennifer; Rosário, Pedro; Núñez, José Carlos; Nunes, Ana Rita; Moreira, Tânia; Nunes, Tânia
2018-01-01
This study explored mathematics teachers’ conceptions of the homework feedback focusing on four key aspects: definition, purpose, types, and perceived impact. Forty-seven teachers from elementary and middle schools participated in six focus groups. Data were analyzed using content analysis. To enhance the trustworthiness of findings, classroom observations were used for triangulation of data. Participants conceptualized homework feedback in three directions (i.e., teachers’ feedback provided to students, students’ feedback provided to teachers, and homework self-feedback), being teachers’ monitoring of students’ learning the purpose reported by most teachers. Participants also reported the types of homework feedback more frequently used in class (e.g., checking homework completion, checking homework on the board), and their perceived impact on students. Findings provide valuable information to deepen the understanding of the homework feedback process, which may help develop new avenues for future research. PMID:29467687
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
Sigrist, Roland; Rauter, Georg; Marchal-Crespo, Laura; Riener, Robert; Wolf, Peter
2015-03-01
Concurrent augmented feedback has been shown to be less effective for learning simple motor tasks than for complex tasks. However, as mostly artificial tasks have been investigated, transfer of results to tasks in sports and rehabilitation remains unknown. Therefore, in this study, the effect of different concurrent feedback was evaluated in trunk-arm rowing. It was then investigated whether multimodal audiovisual and visuohaptic feedback are more effective for learning than visual feedback only. Naïve subjects (N = 24) trained in three groups on a highly realistic virtual reality-based rowing simulator. In the visual feedback group, the subject's oar was superimposed to the target oar, which continuously became more transparent when the deviation between the oars decreased. Moreover, a trace of the subject's trajectory emerged if deviations exceeded a threshold. The audiovisual feedback group trained with oar movement sonification in addition to visual feedback to facilitate learning of the velocity profile. In the visuohaptic group, the oar movement was inhibited by path deviation-dependent braking forces to enhance learning of spatial aspects. All groups significantly decreased the spatial error (tendency in visual group) and velocity error from baseline to the retention tests. Audiovisual feedback fostered learning of the velocity profile significantly more than visuohaptic feedback. The study revealed that well-designed concurrent feedback fosters complex task learning, especially if the advantages of different modalities are exploited. Further studies should analyze the impact of within-feedback design parameters and the transferability of the results to other tasks in sports and rehabilitation.
Time-delay signature of chaos in 1550 nm VCSELs with variable-polarization FBG feedback.
Li, Yan; Wu, Zheng-Mao; Zhong, Zhu-Qiang; Yang, Xian-Jie; Mao, Song; Xia, Guang-Qiong
2014-08-11
Based on the framework of spin-flip model (SFM), the output characteristics of a 1550 nm vertical-cavity surface-emitting laser (VCSEL) subject to variable-polarization fiber Bragg grating (FBG) feedback (VPFBGF) have been investigated. With the aid of the self-correlation function (SF) and the permutation entropy (PE) function, the time-delay signature (TDS) of chaos in the VPFBGF-VCSEL is evaluated, and then the influences of the operation parameters on the TDS of chaos are analyzed. The results show that the TDS of chaos can be suppressed efficiently through selecting suitable coupling coefficient and feedback rate of the FBG, and is weaker than that of chaos generated by traditional variable-polarization mirror feedback VCSELs (VPMF-VCSELs) or polarization-preserved FBG feedback VCSELs (PPFBGF-VCSELs).
DOE Office of Scientific and Technical Information (OSTI.GOV)
Geng, Rongli; Freyberger, Arne P.; Legg, Robert A.
Several new accelerator projects are adopting superconducting accelerator technology. When accelerating cavities maintain high RF gradients, field emission, the emission of electrons from cavity walls, can occur and may impact operational cavity gradient, radiological environment via activated components, and reliability. In this talk, we will discuss instrumented measurements of field emission from the two 1.1 GeV superconducting continuous wave (CW) linacs in CEBAF. The goal is to improve the understanding of field emission sources originating from cryomodule production, installation and operation. Such basic knowledge is needed in guiding field emission control, mitigation, and reduction toward high gradient and reliable operationmore » of superconducting accelerators.« less
The Bonn Electron Stretcher Accelerator ELSA: Past and future
NASA Astrophysics Data System (ADS)
Hillert, W.
2006-05-01
In 1953, it was decided to build a 500MeV electron synchrotron in Bonn. It came into operation 1958, being the first alternating gradient synchrotron in Europe. After five years of performing photoproduction experiments at this accelerator, a larger 2.5GeV electron synchrotron was built and set into operation in 1967. Both synchrotrons were running for particle physics experiments, until from 1982 to 1987 a third accelerator, the electron stretcher ring ELSA, was constructed and set up in a separate ring tunnel below the physics institute. ELSA came into operation in 1987, using the pulsed 2.5GeV synchrotron as pre-accelerator. ELSA serves either as storage ring producing synchrotron radiation, or as post-accelerator and pulse stretcher. Applying a slow extraction close to a third integer resonance, external electron beams with energies up to 3.5GeV and high duty factors are delivered to hadron physics experiments. Various photo- and electroproduction experiments, utilising the experimental set-ups PHOENICS, ELAN, SAPHIR, GDH and Crystal Barrel have been carried out. During the late 90's, a pulsed GaAs source of polarised electrons was constructed and set up at the accelerator. ELSA was upgraded in order to accelerate polarised electrons, compensating for depolarising resonances by applying the methods of fast tune jumping and harmonic closed orbit correction. With the experimental investigation of the GDH sum rule, the first experiment requiring a polarised beam and a polarised target was successfully performed at the accelerator. In the near future, the stretcher ring will be further upgraded to increase polarisation and current of the external electron beams. In addition, the aspects of an increase of the maximum energy to 5GeV using superconducting resonators will be investigated.
1984-07-01
34robustness" analysis for multiloop feedback systems. Reference [55] describes a simple method based on the Perron - Frobenius Theory of non-negative...Viewpoint, " Operator Theory : Advances and Applications, 12, pp. 277-302, 1984. - E. A. Jonckheere, "New Bound on the Sensitivity -- of the Solution of...Reidel, Dordrecht, Holland, 1984. M. G. Safonov, "Comments on Singular Value Theory in Uncertain Feedback Systems, " to appear IEEE Trans. on Automatic
Compact Torus Acceleration and Injection Experiment
NASA Astrophysics Data System (ADS)
Fukumoto, Naoyuki; Fujiwara, Makoto; Nagata, Masayoshi; Uyama, Tadao; Oda, Yasushi; Azuma, Kingo
1996-11-01
The spheromak-type compact torus (CT) acceleration and injection experiment has been carried out using the Himeji Institute of Technology Compact Torus Injector (HIT-CTI). We explore the possibility of refueling, density control, current drive, and edge electric field control of tokamak plasma by means of CT injection. In last September the new HIT-CTI was built up to achieve higher speed (Vct>200 km/s) and higher density CT plasmoid by improving the capacitor bank system and eliminating the impurity and neutral particles. At initial formation discharge tests the gun for formation and compression successfully produced a CT plasmoid and injected it between electrodes for acceleration. (Initial velocity Vct.ini. 32 km/s, Bct 1 kG, Rct=5.5 cm). The formation capacitor bank will be upgraded to two 36 mF capacitors operating at 20 kV (14.4 kJ). The acceleration capacitor bank will be also upgraded to two 36 mF capacitors operating at 20 kV (14.4 kJ). The HIT-CTI will be optimized to obtain suitable CT parameters after acceleration (Bct>5 kG, Lct 20 cm, Vct>200 km/s). In the respect of CT parameter measurement magnetic probes and a He-Ne laser interferometer will be employed in order to measure the CT magnetic field, velocity, density, and length. CT acceleration experimental data on the HIT-CTI and the plan of CT injection experiment on the JFT-2M tokamak (JAERI) will be presented at the meeting.
Electron linear accelerator system for natural rubber vulcanization
NASA Astrophysics Data System (ADS)
Rimjaem, S.; Kongmon, E.; Rhodes, M. W.; Saisut, J.; Thongbai, C.
2017-09-01
Development of an electron accelerator system, beam diagnostic instruments, an irradiation apparatus and electron beam processing methodology for natural rubber vulcanization is underway at the Plasma and Beam Physics Research Facility, Chiang Mai University, Thailand. The project is carried out with the aims to improve the qualities of natural rubber products. The system consists of a DC thermionic electron gun, 5-cell standing-wave radio-frequency (RF) linear accelerator (linac) with side-coupling cavities and an electron beam irradiation apparatus. This system is used to produce electron beams with an adjustable energy between 0.5 and 4 MeV and a pulse current of 10-100 mA at a pulse repetition rate of 20-400 Hz. An average absorbed dose between 160 and 640 Gy is expected to be archived for 4 MeV electron beam when the accelerator is operated at 400 Hz. The research activities focus firstly on assembling of the accelerator system, study on accelerator properties and electron beam dynamic simulations. The resonant frequency of the RF linac in π/2 operating mode is 2996.82 MHz for the operating temperature of 35 °C. The beam dynamic simulations were conducted by using the code ASTRA. Simulation results suggest that electron beams with an average energy of 4.002 MeV can be obtained when the linac accelerating gradient is 41.7 MV/m. The rms transverse beam size and normalized rms transverse emittance at the linac exit are 0.91 mm and 10.48 π mm·mrad, respectively. This information can then be used as the input data for Monte Carlo simulations to estimate the electron beam penetration depth and dose distribution in the natural rubber latex. The study results from this research will be used to define optimal conditions for natural rubber vulcanization with different electron beam energies and doses. This is very useful for development of future practical industrial accelerator units.
Comparison of Acceleration Techniques for Selected Low-Level Bioinformatics Operations
Langenkämper, Daniel; Jakobi, Tobias; Feld, Dustin; Jelonek, Lukas; Goesmann, Alexander; Nattkemper, Tim W.
2016-01-01
Within the recent years clock rates of modern processors stagnated while the demand for computing power continued to grow. This applied particularly for the fields of life sciences and bioinformatics, where new technologies keep on creating rapidly growing piles of raw data with increasing speed. The number of cores per processor increased in an attempt to compensate for slight increments of clock rates. This technological shift demands changes in software development, especially in the field of high performance computing where parallelization techniques are gaining in importance due to the pressing issue of large sized datasets generated by e.g., modern genomics. This paper presents an overview of state-of-the-art manual and automatic acceleration techniques and lists some applications employing these in different areas of sequence informatics. Furthermore, we provide examples for automatic acceleration of two use cases to show typical problems and gains of transforming a serial application to a parallel one. The paper should aid the reader in deciding for a certain techniques for the problem at hand. We compare four different state-of-the-art automatic acceleration approaches (OpenMP, PluTo-SICA, PPCG, and OpenACC). Their performance as well as their applicability for selected use cases is discussed. While optimizations targeting the CPU worked better in the complex k-mer use case, optimizers for Graphics Processing Units (GPUs) performed better in the matrix multiplication example. But performance is only superior at a certain problem size due to data migration overhead. We show that automatic code parallelization is feasible with current compiler software and yields significant increases in execution speed. Automatic optimizers for CPU are mature and usually no additional manual adjustment is required. In contrast, some automatic parallelizers targeting GPUs still lack maturity and are limited to simple statements and structures. PMID:26904094
Comparison of Acceleration Techniques for Selected Low-Level Bioinformatics Operations.
Langenkämper, Daniel; Jakobi, Tobias; Feld, Dustin; Jelonek, Lukas; Goesmann, Alexander; Nattkemper, Tim W
2016-01-01
Within the recent years clock rates of modern processors stagnated while the demand for computing power continued to grow. This applied particularly for the fields of life sciences and bioinformatics, where new technologies keep on creating rapidly growing piles of raw data with increasing speed. The number of cores per processor increased in an attempt to compensate for slight increments of clock rates. This technological shift demands changes in software development, especially in the field of high performance computing where parallelization techniques are gaining in importance due to the pressing issue of large sized datasets generated by e.g., modern genomics. This paper presents an overview of state-of-the-art manual and automatic acceleration techniques and lists some applications employing these in different areas of sequence informatics. Furthermore, we provide examples for automatic acceleration of two use cases to show typical problems and gains of transforming a serial application to a parallel one. The paper should aid the reader in deciding for a certain techniques for the problem at hand. We compare four different state-of-the-art automatic acceleration approaches (OpenMP, PluTo-SICA, PPCG, and OpenACC). Their performance as well as their applicability for selected use cases is discussed. While optimizations targeting the CPU worked better in the complex k-mer use case, optimizers for Graphics Processing Units (GPUs) performed better in the matrix multiplication example. But performance is only superior at a certain problem size due to data migration overhead. We show that automatic code parallelization is feasible with current compiler software and yields significant increases in execution speed. Automatic optimizers for CPU are mature and usually no additional manual adjustment is required. In contrast, some automatic parallelizers targeting GPUs still lack maturity and are limited to simple statements and structures.
1978-11-01
R 2. GOVT A $ SION NO. 3 RIEqLPýIVT’S.;TALOG NUMBER r/ 4. TITLE (and wbiFflT, -L M4 1 , FEEDBACK SYSTEM THEORY ~r Inter in- 6. PERFORMING ORG. REPORT...ANNUAL REPORT FEEDBACK SYSTEM THEORY AFOSR GRANT NO. 76-2946B Air Force Office of Scientific Research for year ending October 31, 1978 79 02 08 L|I...re less stringent than in other synthesis techniques which cannot handle significant parameter uncertainty. _I FEEDBACK SYSTEM THEORY 1. Introduction
The conversion of CESR to operate as the Test Accelerator, CesrTA. Part 1: overview
NASA Astrophysics Data System (ADS)
Billing, M. G.
2015-07-01
Cornell's electron/positron storage ring (CESR) was modified over a series of accelerator shutdowns beginning in May 2008, which substantially improves its capability for research and development for particle accelerators. CESR's energy span from 1.8 to 5.6 GeV with both electrons and positrons makes it ideal for the study of a wide spectrum of accelerator physics issues and instrumentation related to present light sources and future lepton damping rings. Additionally a number of these are also relevant for the beam physics of proton accelerators. This paper outlines the motivation, design and conversion of CESR to a test accelerator, CESRTA, enhanced to study such subjects as low emittance tuning methods, electron cloud (EC) effects, intra-beam scattering, fast ion instabilities as well as general improvements to beam instrumentation. While the initial studies of CESRTA focussed on questions related to the International Linear Collider (ILC) damping ring design, CESRTA is a very flexible storage ring, capable of studying a wide range of accelerator physics and instrumentation questions. This paper contains the outline and the basis for a set of papers documenting the reconfiguration of the storage ring and the associated instrumentation required for the studies described above. Further details may be found in these papers.
NASA Astrophysics Data System (ADS)
Khoder, Mulham; Van der Sande, Guy; Danckaert, Jan; Verschaffelt, Guy
2016-05-01
It is well known that the performance of semiconductor lasers is very sensitive to external optical feedback. This feedback can lead to changes in lasing characteristics and a variety of dynamical effects including chaos and coherence collapse. One way to avoid this external feedback is by using optical isolation, but these isolators and their packaging will increase the cost of the total system. Semiconductor ring lasers nowadays are promising sources in photonic integrated circuits because they do not require cleaved facets or mirrors to form a laser cavity. Recently, some of us proposed to combine semiconductor ring lasers with on chip filtered optical feedback to achieve tunable lasers. The feedback is realized by employing two arrayed waveguide gratings to split/recombine light into different wavelength channels. Semiconductor optical amplifier gates are used to control the feedback strength. In this work, we investigate how such lasers with filtered feedback are influenced by an external conventional optical feedback. The experimental results show intensity fluctuations in the time traces in both the clockwise and counterclockwise directions due to the conventional feedback. We quantify the strength of the conventional feedback induced dynamics be extracting the standard deviation of the intensity fluctuations in the time traces. By using filtered feedback, we can shift the onset of the conventional feedback induced dynamics to larger values of the feedback rate [ Khoder et al, IEEE Photon. Technol. Lett. DOI: 10.1109/LPT.2016.2522184]. The on-chip filtered optical feedback thus makes the semiconductor ring laser less senstive to the effect of (long) conventional optical feedback. We think these conclusions can be extended to other types of lasers.
Op. Amps in Power Amplification: A Laboratory Exercise on Feedback.
ERIC Educational Resources Information Center
Borcherds, P. H.
1984-01-01
To demonstrate negative feedback a power amplifier is constructed from an operational amplifier together with a complementary pair of transistors as an output stage. The amplifier is developed and tested stage by stage, and at each stage the defects apparent at the previous stage are eliminated. (JN)
Compact RF ion source for industrial electrostatic ion accelerator
NASA Astrophysics Data System (ADS)
Kwon, Hyeok-Jung; Park, Sae-Hoon; Kim, Dae-Il; Cho, Yong-Sub
2016-02-01
Korea Multi-purpose Accelerator Complex is developing a single-ended electrostatic ion accelerator to irradiate gaseous ions, such as hydrogen and nitrogen, on materials for industrial applications. ELV type high voltage power supply has been selected. Because of the limited space, electrical power, and robust operation, a 200 MHz RF ion source has been developed. In this paper, the accelerator system, test stand of the ion source, and its test results are described.
Compact RF ion source for industrial electrostatic ion accelerator.
Kwon, Hyeok-Jung; Park, Sae-Hoon; Kim, Dae-Il; Cho, Yong-Sub
2016-02-01
Korea Multi-purpose Accelerator Complex is developing a single-ended electrostatic ion accelerator to irradiate gaseous ions, such as hydrogen and nitrogen, on materials for industrial applications. ELV type high voltage power supply has been selected. Because of the limited space, electrical power, and robust operation, a 200 MHz RF ion source has been developed. In this paper, the accelerator system, test stand of the ion source, and its test results are described.
Miniature penetrator (MinPen) acceleration recorder development test
DOE Office of Scientific and Technical Information (OSTI.GOV)
Franco, R.J.; Platzbecker, M.R.
1998-08-01
The Telemetry Technology Development Department at Sandia National Laboratories actively develops and tests acceleration recorders for penetrating weapons. This new acceleration recorder (MinPen) utilizes a microprocessor-based architecture for operational flexibility while maintaining electronics and packaging techniques developed over years of penetrator testing. MinPen has been demonstrated to function in shock environments up to 20,000 Gs. The MinPen instrumentation development has resulted in a rugged, versatile, miniature acceleration recorder and is a valuable tool for penetrator testing in a wide range of applications.
Acceleration modules in linear induction accelerators
NASA Astrophysics Data System (ADS)
Wang, Shao-Heng; Deng, Jian-Jun
2014-05-01
The Linear Induction Accelerator (LIA) is a unique type of accelerator that is capable of accelerating kilo-Ampere charged particle current to tens of MeV energy. The present development of LIA in MHz bursting mode and the successful application into a synchrotron have broadened LIA's usage scope. Although the transformer model is widely used to explain the acceleration mechanism of LIAs, it is not appropriate to consider the induction electric field as the field which accelerates charged particles for many modern LIAs. We have examined the transition of the magnetic cores' functions during the LIA acceleration modules' evolution, distinguished transformer type and transmission line type LIA acceleration modules, and re-considered several related issues based on transmission line type LIA acceleration module. This clarified understanding should help in the further development and design of LIA acceleration modules.
Cryogenics for high-energy particle accelerators: highlights from the first fifty years
NASA Astrophysics Data System (ADS)
Lebrun, Ph
2017-02-01
Applied superconductivity has become a key technology for high-energy particle accelerators, allowing to reach higher beam energy while containing size, capital expenditure and operating costs. Large and powerful cryogenic systems are therefore ancillary to low-temperature superconducting accelerator devices - magnets and high-frequency cavities - distributed over multi-kilometre distances and operating generally close to the normal boiling point of helium, but also above 4.2 K in supercritical and down to below 2 K in superfluid. Additionally, low-temperature operation in accelerators may also be required by considerations of ultra-high vacuum, limited stored energy and beam stability. We discuss the rationale for cryogenics in high-energy particle accelerators, review its development over the past half-century and present its outlook in future large projects, with reference to the main engineering domains of cryostat design and heat loads, cooling schemes, efficient power refrigeration and cryogenic fluid management.
NASA Technical Reports Server (NTRS)
Parker, Linda Neergaard; Zank, Gary P.
2013-01-01
We present preliminary results from a model that diffusively accelerates particles at multiple shocks. Our basic approach is related to box models (Protheroe and Stanev, 1998; Moraal and Axford, 1983; Ball and Kirk, 1992; Drury et al., 1999) in which a distribution of particles is diffusively accelerated inside the box while simultaneously experiencing decompression through adiabatic expansion and losses from the convection and diffusion of particles outside the box (Melrose and Pope, 1993; Zank et al., 2000). We adiabatically decompress the accelerated particle distribution between each shock by either the method explored in Melrose and Pope (1993) and Pope and Melrose (1994) or by the approach set forth in Zank et al. (2000) where we solve the transport equation by a method analogous to operator splitting. The second method incorporates the additional loss terms of convection and diffusion and allows for the use of a variable time between shocks. We use a maximum injection energy (Emax) appropriate for quasi-parallel and quasi-perpendicular shocks (Zank et al., 2000, 2006; Dosch and Shalchi, 2010) and provide a preliminary application of the diffusive acceleration of particles by multiple shocks with frequencies appropriate for solar maximum (i.e., a non-Markovian process).
Force feedback in a piezoelectric linear actuator for neurosurgery.
De Lorenzo, Danilo; De Momi, Elena; Dyagilev, Ilya; Manganelli, Rudy; Formaglio, Alessandro; Prattichizzo, Domenico; Shoham, Moshe; Ferrigno, Giancarlo
2011-09-01
Force feedback in robotic minimally invasive surgery allows the human operator to manipulate tissues as if his/her hands were in contact with the patient organs. A force sensor mounted on the probe raises problems with sterilization of the overall surgical tool. Also, the use of off-axis gauges introduces a moment that increases the friction force on the bearing, which can easily mask off the signal, given the small force to be measured. This work aims at designing and testing two methods for estimating the resistance to the advancement (force) experienced by a standard probe for brain biopsies within a brain-like material. The further goal is to provide a neurosurgeon using a master-slave tele-operated driver with direct feedback on the tissue mechanical characteristics. Two possible sensing methods, in-axis strain gauge force sensor and position-position error (control-based method), were implemented and tested, both aimed at device miniaturization. The analysis carried out was aimed at fulfilment of the psychophysics requirements for force detection and delay tolerance, also taking into account safety, which is directly related to the last two issues. Controller parameters definition is addressed and consideration is given to development of the device with integration of a haptic interface. Results show better performance of the control-based method (RMSE < 0.1 N), which is also best for reliability, sterilizability, and material dimensions for the application addressed. The control-based method developed for force estimation is compatible with the neurosurgical application and is also capable of measuring tissue resistance without any additional sensors. Force feedback in minimally invasive surgery allows the human operator to manipulate tissues as if his/her hands were in contact with the patient organs. Copyright © 2011 John Wiley & Sons, Ltd.
ERIC Educational Resources Information Center
Patchan, Melissa M.; Schunn, Christian D.; Correnti, Richard J.
2016-01-01
Although feedback is often seen as a critical component of the learning process, many open questions about how specific feedback features contribute to the effectiveness of feedback remain--especially in regards to peer feedback of writing. Nelson and Schunn (2009) identified several important features of peer feedback in their nature of feedback…
Is Africa a 'Graveyard' for Linear Accelerators?
Reichenvater, H; Matias, L Dos S
2016-12-01
Linear accelerator downtimes are common and problematic in many African countries and may jeopardise the outcome of affected radiation treatments. The predicted increase in cancer incidence and prevalence on the African continent will require, inter alia, improved response with regard to a reduction in linear accelerator downtimes. Here we discuss the problems associated with the maintenance and repair of linear accelerators and propose alternative solutions relevant for local conditions in African countries. The paper is based on about four decades of experience in capacity building, installing, commissioning, calibrating, servicing and repairing linear accelerators in Africa, where about 40% of the low and middle income countries in the world are geographically located. Linear accelerators can successfully be operated, maintained and repaired in African countries provided proper maintenance and repair plans are put in place and executed. Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Parker, L. N.; Zank, G. P.
2013-12-01
Successful forecasting of energetic particle events in space weather models require algorithms for correctly predicting the spectrum of ions accelerated from a background population of charged particles. We present preliminary results from a model that diffusively accelerates particles at multiple shocks. Our basic approach is related to box models (Protheroe and Stanev, 1998; Moraal and Axford, 1983; Ball and Kirk, 1992; Drury et al., 1999) in which a distribution of particles is diffusively accelerated inside the box while simultaneously experiencing decompression through adiabatic expansion and losses from the convection and diffusion of particles outside the box (Melrose and Pope, 1993; Zank et al., 2000). We adiabatically decompress the accelerated particle distribution between each shock by either the method explored in Melrose and Pope (1993) and Pope and Melrose (1994) or by the approach set forth in Zank et al. (2000) where we solve the transport equation by a method analogous to operator splitting. The second method incorporates the additional loss terms of convection and diffusion and allows for the use of a variable time between shocks. We use a maximum injection energy (Emax) appropriate for quasi-parallel and quasi-perpendicular shocks (Zank et al., 2000, 2006; Dosch and Shalchi, 2010) and provide a preliminary application of the diffusive acceleration of particles by multiple shocks with frequencies appropriate for solar maximum (i.e., a non-Markovian process).
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…
The solution of the point kinetics equations via converged accelerated Taylor series (CATS)
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ganapol, B.; Picca, P.; Previti, A.
This paper deals with finding accurate solutions of the point kinetics equations including non-linear feedback, in a fast, efficient and straightforward way. A truncated Taylor series is coupled to continuous analytical continuation to provide the recurrence relations to solve the ordinary differential equations of point kinetics. Non-linear (Wynn-epsilon) and linear (Romberg) convergence accelerations are employed to provide highly accurate results for the evaluation of Taylor series expansions and extrapolated values of neutron and precursor densities at desired edits. The proposed Converged Accelerated Taylor Series, or CATS, algorithm automatically performs successive mesh refinements until the desired accuracy is obtained, making usemore » of the intermediate results for converged initial values at each interval. Numerical performance is evaluated using case studies available from the literature. Nearly perfect agreement is found with the literature results generally considered most accurate. Benchmark quality results are reported for several cases of interest including step, ramp, zigzag and sinusoidal prescribed insertions and insertions with adiabatic Doppler feedback. A larger than usual (9) number of digits is included to encourage honest benchmarking. The benchmark is then applied to the enhanced piecewise constant algorithm (EPCA) currently being developed by the second author. (authors)« less
Divertor power load feedback with nitrogen seeding in ASDEX Upgrade
NASA Astrophysics Data System (ADS)
Kallenbach, A.; Dux, R.; Fuchs, J. C.; Fischer, R.; Geiger, B.; Giannone, L.; Herrmann, A.; Lunt, T.; Mertens, V.; McDermott, R.; Neu, R.; Pütterich, T.; Rathgeber, S.; Rohde, V.; Schmid, K.; Schweinzer, J.; Treutterer, W.; ASDEX Upgrade Team
2010-05-01
Feedback control of the divertor power load by means of nitrogen seeding has been developed into a routine operational tool in the all-tungsten clad ASDEX Upgrade tokamak. For heating powers above about 12 MW, its use has become inevitable to protect the divertor tungsten coating under boronized conditions. The use of nitrogen seeding is accompanied by improved energy confinement due to higher core plasma temperatures, which more than compensates the negative effect of plasma dilution by nitrogen on the neutron rate. This paper describes the technical details of the feedback controller. A simple model for its underlying physics allows the prediction of its behaviour and the optimization of the feedback gain coefficients used. Storage and release of nitrogen in tungsten surfaces were found to have substantial impact on the behaviour of the seeded plasma, resulting in increased nitrogen consumption with unloaded walls and a latency of nitrogen release over several discharges after its injection. Nitrogen is released from tungsten plasma facing components with moderate surface temperature in a sputtering-like process; therefore no uncontrolled excursions of the nitrogen wall release are observed. Overall, very stable operation of the high-Z tokamak is possible with nitrogen seeding, where core radiative losses are avoided due to its low atomic charge Z and a high ELM frequency is maintained.
Virtual Reality Cerebral Aneurysm Clipping Simulation With Real-time Haptic Feedback
Alaraj, Ali; Luciano, Cristian J.; Bailey, Daniel P.; Elsenousi, Abdussalam; Roitberg, Ben Z.; Bernardo, Antonio; Banerjee, P. Pat; Charbel, Fady T.
2014-01-01
Background With the decrease in the number of cerebral aneurysms treated surgically and the increase of complexity of those treated surgically, there is a need for simulation-based tools to teach future neurosurgeons the operative techniques of aneurysm clipping. Objective To develop and evaluate the usefulness of a new haptic-based virtual reality (VR) simulator in the training of neurosurgical residents. Methods A real-time sensory haptic feedback virtual reality aneurysm clipping simulator was developed using the Immersive Touch platform. A prototype middle cerebral artery aneurysm simulation was created from a computed tomography angiogram. Aneurysm and vessel volume deformation and haptic feedback are provided in a 3-D immersive VR environment. Intraoperative aneurysm rupture was also simulated. Seventeen neurosurgery residents from three residency programs tested the simulator and provided feedback on its usefulness and resemblance to real aneurysm clipping surgery. Results Residents felt that the simulation would be useful in preparing for real-life surgery. About two thirds of the residents felt that the 3-D immersive anatomical details provided a very close resemblance to real operative anatomy and accurate guidance for deciding surgical approaches. They believed the simulation is useful for preoperative surgical rehearsal and neurosurgical training. One third of the residents felt that the technology in its current form provided very realistic haptic feedback for aneurysm surgery. Conclusion Neurosurgical residents felt that the novel immersive VR simulator is helpful in their training especially since they do not get a chance to perform aneurysm clippings until very late in their residency programs. PMID:25599200
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…
NASA Astrophysics Data System (ADS)
Bajaj, Nikhil; Chiu, George T.-C.; Rhoads, Jeffrey F.
2018-07-01
Vibration-based sensing modalities traditionally have relied upon monitoring small shifts in natural frequency in order to detect structural changes (such as those in mass or stiffness). In contrast, bifurcation-based sensing schemes rely on the detection of a qualitative change in the behavior of a system as a parameter is varied. This can produce easy-to-detect changes in response amplitude with high sensitivity to structural change, but requires resonant devices with specific dynamic behavior which is not always easily reproduced. Desirable behavior for such devices can be produced reliably via nonlinear feedback circuitry, but has in past efforts been largely limited to sub-MHz operation, partially due to the time delay limitations present in certain nonlinear feedback circuits, such as multipliers. This work demonstrates the design and implementation of a piecewise-linear resonator realized via diode- and integrated circuit-based feedback electronics and a quartz crystal resonator. The proposed system is fabricated and characterized, and the creation and selective placement of the bifurcation points of the overall electromechanical system is demonstrated by tuning the circuit gains. The demonstrated circuit operates at 16 MHz. Preliminary modeling and analysis is presented that qualitatively agrees with the experimentally-observed behavior.
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.
NASA Astrophysics Data System (ADS)
Salathé, Yves; Kurpiers, Philipp; Karg, Thomas; Lang, Christian; Andersen, Christian Kraglund; Akin, Abdulkadir; Krinner, Sebastian; Eichler, Christopher; Wallraff, Andreas
2018-03-01
Quantum computing architectures rely on classical electronics for control and readout. Employing classical electronics in a feedback loop with the quantum system allows us to stabilize states, correct errors, and realize specific feedforward-based quantum computing and communication schemes such as deterministic quantum teleportation. These feedback and feedforward operations are required to be fast compared to the coherence time of the quantum system to minimize the probability of errors. We present a field-programmable-gate-array-based digital signal processing system capable of real-time quadrature demodulation, a determination of the qubit state, and a generation of state-dependent feedback trigger signals. The feedback trigger is generated with a latency of 110 ns with respect to the timing of the analog input signal. We characterize the performance of the system for an active qubit initialization protocol based on the dispersive readout of a superconducting qubit and discuss potential applications in feedback and feedforward algorithms.
Gong, Jian; Kim, Chang-Jin “CJ”
2009-01-01
Electrowetting-on-dielectric (EWOD) actuation enables digital (or droplet) microfluidics where small packets of liquids are manipulated on a two-dimensional surface. Due to its mechanical simplicity and low energy consumption, EWOD holds particular promise for portable systems. To improve volume precision of the droplets, which is desired for quantitative applications such as biochemical assays, existing practices would require near-perfect device fabricaion and operation conditions unless the droplets are generated under feedback control by an extra pump setup off of the chip. In this paper, we develop an all-electronic (i.e., no ancillary pumping) real-time feedback control of on-chip droplet generation. A fast voltage modulation, capacitance sensing, and discrete-time PID feedback controller are integrated on the operating electronic board. A significant improvement is obtained in the droplet volume uniformity, compared with an open loop control as well as the previous feedback control employing an external pump. Furthermore, this new capability empowers users to prescribe the droplet volume even below the previously considered minimum, allowing, for example, 1:x (x < 1) mixing, in comparison to the previously considered n:m mixing (i.e., n and m unit droplets). PMID:18497909
Gong, Jian; Kim, Chang-Jin C J
2008-06-01
Electrowetting-on-dielectric (EWOD) actuation enables digital (or droplet) microfluidics where small packets of liquids are manipulated on a two-dimensional surface. Due to its mechanical simplicity and low energy consumption, EWOD holds particular promise for portable systems. To improve volume precision of the droplets, which is desired for quantitative applications such as biochemical assays, existing practices would require near-perfect device fabrication and operation conditions unless the droplets are generated under feedback control by an extra pump setup off of the chip. In this paper, we develop an all-electronic (i.e., no ancillary pumping) real-time feedback control of on-chip droplet generation. A fast voltage modulation, capacitance sensing, and discrete-time PID feedback controller are integrated on the operating electronic board. A significant improvement is obtained in the droplet volume uniformity, compared with an open loop control as well as the previous feedback control employing an external pump. Furthermore, this new capability empowers users to prescribe the droplet volume even below the previously considered minimum, allowing, for example, 1 : x (x < 1) mixing, in comparison to the previously considered n : m mixing (i.e., n and m unit droplets).
The purpose of this SOP is to describe the steps involved in cleaning the electronic data generated from data entry of the Questionnaire Feedback form. It applies to electronic data corresponding to the Questionnaire Feedback form that was scanned and verified by the data staff ...
NASA Technical Reports Server (NTRS)
Lau, William K.; Kyu-Myong, Kim; Yasunari, Teppei; Gautam, Ritesh; Hsu, Christina
2011-01-01
The impacts of absorbing aerosol on melting of snowpack in the Hindu-Kush-Himalayas-Tibetan Plateau (HKHT) region are studied using in-situ, satellite observations, and GEOS-5 GCM. Based on atmospheric black carbon measurements from the Pyramid observation ( 5 km elevation) in Mt. Everest, we estimate that deposition of black carbon on snow surface will give rise to a reduction in snow surface albedo of 2- 5 %, and an increased annual runoff of 12-34% for a typical Tibetan glacier. Examination of satellite reflectivity and re-analysis data reveals signals of possible impacts of dust and black carbon in darkening the snow surface, and accelerating spring melting of snowpack in the HKHT, following a build-up of absorbing aerosols in the Indo-Gangetic Plain. Results from GCM experiments show that 8-10% increase in the rate of melting of snowpack over the western Himalayas and Tibetan Plateau can be attributed to the elevated-heat-pump (EHP) feedback effect, initiated from the absorption of solar radiation by dust and black carbon accumulated to great height ( 5 km) over the Indo-Gangetic Plain and Himalayas foothills in the pre-monsoon season (April-May). The accelerated melting of the snowpack is enabled by an EHP-induced atmosphere-land-snowpack positive feedback involving a) orographic forcing of the monsoon flow by the complex terrain, and thermal forcing of the HKHT region, leading to increased moisture, cloudiness and rainfall over the Himalayas foothills and northern India, b) warming of the upper troposphere over the Tibetan Plateau, and c) an snow albedo-temperature feedback initiated by a transfer of latent and sensible heat from a warmer atmosphere over the HKHT to the underlying snow surface. Results from ongoing modeling work to assess the relative roles of EHP vs. snow-darkening effects on accelerated melting of snowpack in HKHT region will also be discussed.
NASA Technical Reports Server (NTRS)
Goodman, S. J.; Lapenta, W.; Jedlovec, G.; Dodge, J.; Bradshaw, T.
2003-01-01
The NASA Short-term Prediction Research and Transition (SPoRT) Center in Huntsville, Alabama was created to accelerate the infusion of NASA earth science observations, data assimilation and modeling research into NWS forecast operations and decision-making. The principal focus of experimental products is on the regional scale with an emphasis on forecast improvements on a time scale of 0-24 hours. The SPoRT Center research is aligned with the regional prediction objectives of the US Weather Research Program dealing with 0-1 day forecast issues ranging from convective initiation to 24-hr quantitative precipitation forecasting. The SPoRT Center, together with its other interagency partners, universities, and the NASA/NOAA Joint Center for Satellite Data Assimilation, provides a means and a process to effectively transition NASA Earth Science Enterprise observations and technology to National Weather Service operations and decision makers at both the global/national and regional scales. This paper describes the process for the transition of experimental products into forecast operations, current products undergoing assessment by forecasters, and plans for the future.
Residual entanglement of accelerated fermions is not nonlocal
DOE Office of Scientific and Technical Information (OSTI.GOV)
Friis, Nicolai; Koehler, Philipp; Bertlmann, Reinhold A.
2011-12-15
We analyze the operational meaning of the residual entanglement in noninertial fermionic systems in terms of the achievable violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality. We demonstrate that the quantum correlations of fermions, which were previously found to survive in the infinite acceleration limit, cannot be considered to be nonlocal. The entanglement shared by an inertial and an accelerated observer cannot be utilized for the violation of the CHSH inequality in case of high accelerations. Our results are shown to extend beyond the single-mode approximation commonly used in the literature.
Smartphones, Smart Feedback: Using Mobile Devices to Collect In-the-Moment Feedback.
Havel, Lauren Koehler; Powell, Samantha D; Cabaniss, Deborah L; Arbuckle, Melissa R
2017-02-01
The goal of this study was to streamline the collection of resident feedback in order to support faculty development and program improvement in psychiatry training. The authors developed and implemented a brief, free, mobile survey to track resident feedback and class attendance. Prior to instituting this system, resident feedback was obtained semi-annually for each course (n = 90) and not each individual class. In comparison, this new system allowed the authors to collect feedback on 477 of the 519 classes held over the 2014-15 academic year (92 %). Written comments about the curriculum increased over tenfold from 42 in 2013-14 to 541 during a comparative time period in 2014-15. One year after instituting this new system, resident participation increased to 81 % on average (compared to 64 % previously). Mobile devices may provide an inexpensive and relatively untapped mechanism for improving the process of collecting resident feedback and tracking class attendance.
Wangpraseurt, Daniel; Holm, Jacob B.; Larkum, Anthony W. D.; Pernice, Mathieu; Ralph, Peter J.; Suggett, David J.; Kühl, Michael
2017-01-01
Climate change-related coral bleaching, i.e., the visible loss of zooxanthellae from the coral host, is increasing in frequency and extent and presents a major threat to coral reefs globally. Coral bleaching has been proposed to involve accelerating light stress of their microalgal endosymbionts via a positive feedback loop of photodamage, symbiont expulsion and excess in vivo light exposure. To test this hypothesis, we used light and O2 microsensors to characterize in vivo light exposure and photosynthesis of Symbiodinium during a thermal stress experiment. We created tissue areas with different densities of Symbiodinium cells in order to understand the optical properties and light microenvironment of corals during bleaching. Our results showed that in bleached Pocillopora damicornis corals, Symbiodinium light exposure was up to fivefold enhanced relative to healthy corals, and the relationship between symbiont loss and light enhancement was well-described by a power-law function. Cell-specific rates of Symbiodinium gross photosynthesis and light respiration were enhanced in bleached P. damicornis compared to healthy corals, while areal rates of net photosynthesis decreased. Symbiodinium light exposure in Favites sp. revealed the presence of low light microniches in bleached coral tissues, suggesting that light scattering in thick coral tissues can enable photoprotection of cryptic symbionts. Our study provides evidence for the acceleration of in vivo light exposure during coral bleaching but this optical feedback mechanism differs between coral hosts. Enhanced photosynthesis in relation to accelerating light exposure shows that coral microscale optics exerts a key role on coral photophysiology and the subsequent degree of radiative stress during coral bleaching. PMID:28174567
Wangpraseurt, Daniel; Holm, Jacob B; Larkum, Anthony W D; Pernice, Mathieu; Ralph, Peter J; Suggett, David J; Kühl, Michael
2017-01-01
Climate change-related coral bleaching, i.e., the visible loss of zooxanthellae from the coral host, is increasing in frequency and extent and presents a major threat to coral reefs globally. Coral bleaching has been proposed to involve accelerating light stress of their microalgal endosymbionts via a positive feedback loop of photodamage, symbiont expulsion and excess in vivo light exposure. To test this hypothesis, we used light and O 2 microsensors to characterize in vivo light exposure and photosynthesis of Symbiodinium during a thermal stress experiment. We created tissue areas with different densities of Symbiodinium cells in order to understand the optical properties and light microenvironment of corals during bleaching. Our results showed that in bleached Pocillopora damicornis corals, Symbiodinium light exposure was up to fivefold enhanced relative to healthy corals, and the relationship between symbiont loss and light enhancement was well-described by a power-law function. Cell-specific rates of Symbiodinium gross photosynthesis and light respiration were enhanced in bleached P. damicornis compared to healthy corals, while areal rates of net photosynthesis decreased. Symbiodinium light exposure in Favites sp. revealed the presence of low light microniches in bleached coral tissues, suggesting that light scattering in thick coral tissues can enable photoprotection of cryptic symbionts. Our study provides evidence for the acceleration of in vivo light exposure during coral bleaching but this optical feedback mechanism differs between coral hosts. Enhanced photosynthesis in relation to accelerating light exposure shows that coral microscale optics exerts a key role on coral photophysiology and the subsequent degree of radiative stress during coral bleaching.
System identification from closed-loop data with known output feedback dynamics
NASA Technical Reports Server (NTRS)
Phan, Minh; Juang, Jer-Nan; Horta, Lucas G.; Longman, Richard W.
1992-01-01
This paper presents a procedure to identify the open loop systems when it is operating under closed loop conditions. First, closed loop excitation data are used to compute the system open loop and closed loop Markov parameters. The Markov parameters, which are the pulse response samples, are then used to compute a state space representation of the open loop system. Two closed loop configurations are considered in this paper. The closed loop system can have either a linear output feedback controller or a dynamic output feedback controller. Numerical examples are provided to illustrate the proposed closed loop identification method.
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. © The Author(s) 2015.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Jumpertz, L., E-mail: louise.jumpertz@telecom-paristech.fr; MirSense, 8 avenue de la Vauve, F-91120 Palaiseau; Michel, F.
2016-01-15
Precise knowledge of the linewidth enhancement factor of a semiconductor laser under actual operating conditions is of prime importance since this parameter dictates various phenomena such as linewidth broadening or optical nonlinearities enhancement. The above-threshold linewidth enhancement factor of a mid-infrared quantum cascade laser structure operated at 10{sup ∘}C is determined experimentally using two different methods based on optical feedback. Both Fabry-Perot and distributed feedback quantum cascade lasers based on the same active area design are studied, the former by following the wavelength shift as a function of the feedback strength and the latter by self-mixing interferometry. The results aremore » consistent and unveil a clear pump current dependence of the linewidth enhancement factor, with values ranging from 0.8 to about 3.« less
Simultaneous operation of two soft x-ray free-electron lasers driven by one linear accelerator
NASA Astrophysics Data System (ADS)
Faatz, B.; Plönjes, E.; Ackermann, S.; Agababyan, A.; Asgekar, V.; Ayvazyan, V.; Baark, S.; Baboi, N.; Balandin, V.; von Bargen, N.; Bican, Y.; Bilani, O.; Bödewadt, J.; Böhnert, M.; Böspflug, R.; Bonfigt, S.; Bolz, H.; Borges, F.; Borkenhagen, O.; Brachmanski, M.; Braune, M.; Brinkmann, A.; Brovko, O.; Bruns, T.; Castro, P.; Chen, J.; Czwalinna, M. K.; Damker, H.; Decking, W.; Degenhardt, M.; Delfs, A.; Delfs, T.; Deng, H.; Dressel, M.; Duhme, H.-T.; Düsterer, S.; Eckoldt, H.; Eislage, A.; Felber, M.; Feldhaus, J.; Gessler, P.; Gibau, M.; Golubeva, N.; Golz, T.; Gonschior, J.; Grebentsov, A.; Grecki, M.; Grün, C.; Grunewald, S.; Hacker, K.; Hänisch, L.; Hage, A.; Hans, T.; Hass, E.; Hauberg, A.; Hensler, O.; Hesse, M.; Heuck, K.; Hidvegi, A.; Holz, M.; Honkavaara, K.; Höppner, H.; Ignatenko, A.; Jäger, J.; Jastrow, U.; Kammering, R.; Karstensen, S.; Kaukher, A.; Kay, H.; Keil, B.; Klose, K.; Kocharyan, V.; Köpke, M.; Körfer, M.; Kook, W.; Krause, B.; Krebs, O.; Kreis, S.; Krivan, F.; Kuhlmann, J.; Kuhlmann, M.; Kube, G.; Laarmann, T.; Lechner, C.; Lederer, S.; Leuschner, A.; Liebertz, D.; Liebing, J.; Liedtke, A.; Lilje, L.; Limberg, T.; Lipka, D.; Liu, B.; Lorbeer, B.; Ludwig, K.; Mahn, H.; Marinkovic, G.; Martens, C.; Marutzky, F.; Maslocv, M.; Meissner, D.; Mildner, N.; Miltchev, V.; Molnar, S.; Mross, D.; Müller, F.; Neumann, R.; Neumann, P.; Nölle, D.; Obier, F.; Pelzer, M.; Peters, H.-B.; Petersen, K.; Petrosyan, A.; Petrosyan, G.; Petrosyan, L.; Petrosyan, V.; Petrov, A.; Pfeiffer, S.; Piotrowski, A.; Pisarov, Z.; Plath, T.; Pototzki, P.; Prandolini, M. J.; Prenting, J.; Priebe, G.; Racky, B.; Ramm, T.; Rehlich, K.; Riedel, R.; Roggli, M.; Röhling, M.; Rönsch-Schulenburg, J.; Rossbach, J.; Rybnikov, V.; Schäfer, J.; Schaffran, J.; Schlarb, H.; Schlesselmann, G.; Schlösser, M.; Schmid, P.; Schmidt, C.; Schmidt-Föhre, F.; Schmitz, M.; Schneidmiller, E.; Schöps, A.; Scholz, M.; Schreiber, S.; Schütt, K.; Schütz, U.; Schulte-Schrepping, H.; Schulz, M.; Shabunov, A.; Smirnov, P.; Sombrowski, E.; Sorokin, A.; Sparr, B.; Spengler, J.; Staack, M.; Stadler, M.; Stechmann, C.; Steffen, B.; Stojanovic, N.; Sychev, V.; Syresin, E.; Tanikawa, T.; Tavella, F.; Tesch, N.; Tiedtke, K.; Tischer, M.; Treusch, R.; Tripathi, S.; Vagin, P.; Vetrov, P.; Vilcins, S.; Vogt, M.; de Zubiaurre Wagner, A.; Wamsat, T.; Weddig, H.; Weichert, G.; Weigelt, H.; Wentowski, N.; Wiebers, C.; Wilksen, T.; Willner, A.; Wittenburg, K.; Wohlenberg, T.; Wortmann, J.; Wurth, W.; Yurkov, M.; Zagorodnov, I.; Zemella, J.
2016-06-01
Extreme-ultraviolet to x-ray free-electron lasers (FELs) in operation for scientific applications are up to now single-user facilities. While most FELs generate around 100 photon pulses per second, FLASH at DESY can deliver almost two orders of magnitude more pulses in this time span due to its superconducting accelerator technology. This makes the facility a prime candidate to realize the next step in FELs—dividing the electron pulse trains into several FEL lines and delivering photon pulses to several users at the same time. Hence, FLASH has been extended with a second undulator line and self-amplified spontaneous emission (SASE) is demonstrated in both FELs simultaneously. FLASH can now deliver MHz pulse trains to two user experiments in parallel with individually selected photon beam characteristics. First results of the capabilities of this extension are shown with emphasis on independent variation of wavelength, repetition rate, and photon pulse length.
Suhoyo, Yoyo; Van Hell, Elisabeth A; Kerdijk, Wouter; Emilia, Ova; Schönrock-Adema, Johanna; Kuks, Jan B M; Cohen-Schotanus, Janke
2017-04-05
Various feedback characteristics have been suggested to positively influence student learning. It is not clear how these feedback characteristics contribute to students' perceived learning value of feedback in cultures classified low on the cultural dimension of individualism and high on power distance. This study was conducted to validate the influence of five feedback characteristics on students' perceived learning value of feedback in an Indonesian clerkship context. We asked clerks in Neurology (n = 169) and Internal Medicine (n = 132) to assess on a 5-point Likert scale the learning value of the feedback they received. We asked them to record whether the feedback provider (1) informed the student what went well, (2) mentioned which aspects of performance needed improvement, (3) compared the student's performance to a standard, (4) further explained or demonstrated the correct performance, and (5) prepared an action plan with the student to improve performance. Data were analyzed using multilevel regression. A total of 250 students participated in this study, 131 from Internal Medicine (response rate 99%) and 119 from Neurology (response rate 70%). Of these participants, 225 respondents (44% males, 56% females) completed the form and reported 889 feedback moments. Students perceived feedback as more valuable when the feedback provider mentioned their weaknesses (β = 0.153, p < 0.01), compared their performance to a standard (β = 0.159, p < 0.01), explained or demonstrated the correct performance (β = 0.324, p < 0.001) and prepared an action plan with the student (β =0.496, p < 0.001). Appraisal of good performance did not influence the perceived learning value of feedback. No gender differences were found for perceived learning value. In Indonesia, we could validate four out of the five characteristics for effective feedback. We argue that our findings relate to culture, in particular to the levels of individualism and power distance. The
Effects of realistic force feedback in a robotic assisted minimally invasive surgery system.
Moradi Dalvand, Mohsen; Shirinzadeh, Bijan; Nahavandi, Saeid; Smith, Julian
2014-06-01
Robotic assisted minimally invasive surgery systems not only have the advantages of traditional laparoscopic procedures but also restore the surgeon's hand-eye coordination and improve the surgeon's precision by filtering hand tremors. Unfortunately, these benefits have come at the expense of the surgeon's ability to feel. Several research efforts have already attempted to restore this feature and study the effects of force feedback in robotic systems. The proposed methods and studies have some shortcomings. The main focus of this research is to overcome some of these limitations and to study the effects of force feedback in palpation in a more realistic fashion. A parallel robot assisted minimally invasive surgery system (PRAMiSS) with force feedback capabilities was employed to study the effects of realistic force feedback in palpation of artificial tissue samples. PRAMiSS is capable of actually measuring the tip/tissue interaction forces directly from the surgery site. Four sets of experiments using only vision feedback, only force feedback, simultaneous force and vision feedback and direct manipulation were conducted to evaluate the role of sensory feedback from sideways tip/tissue interaction forces with a scale factor of 100% in characterising tissues of varying stiffness. Twenty human subjects were involved in the experiments for at least 1440 trials. Friedman and Wilcoxon signed-rank tests were employed to statistically analyse the experimental results. Providing realistic force feedback in robotic assisted surgery systems improves the quality of tissue characterization procedures. Force feedback capability also increases the certainty of characterizing soft tissues compared with direct palpation using the lateral sides of index fingers. The force feedback capability can improve the quality of palpation and characterization of soft tissues of varying stiffness by restoring sense of touch in robotic assisted minimally invasive surgery operations.
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…
Neural substrates of visuomotor learning based on improved feedback control and prediction
Grafton, Scott T.; Schmitt, Paul; Horn, John Van; Diedrichsen, Jörn
2008-01-01
Motor skills emerge from learning feedforward commands as well as improvements in feedback control. These two components of learning were investigated in a compensatory visuomotor tracking task on a trial-by-trial basis. Between trial learning was characterized with a state-space model to provide smoothed estimates of feedforward and feedback learning, separable from random fluctuations in motor performance and error. The resultant parameters were correlated with brain activity using magnetic resonance imaging. Learning related to the generation of a feedforward command correlated with activity in dorsal premotor cortex, inferior parietal lobule, supplementary motor area and cingulate motor area, supporting a role of these areas in retrieving and executing a predictive motor command. Modulation of feedback control was associated with activity in bilateral posterior superior parietal lobule as well as right ventral premotor cortex. Performance error correlated with activity in a widespread cortical and subcortical network including bilateral parietal, premotor and rostral anterior cingulate cortex as well as the cerebellar cortex. Finally, trial-by-trial changes of kinematics, as measured by mean absolute hand acceleration, correlated with activity in motor cortex and anterior cerebellum. The results demonstrate that incremental, learning dependent changes can be modeled on a trial-by-trial basis and neural substrates for feedforward control of novel motor programs are localized to secondary motor areas. PMID:18032069
Feedback model of secondary electron emission in DC gas discharge plasmas
NASA Astrophysics Data System (ADS)
Saravanan, ARUMUGAM; Prince, ALEX; Suraj, Kumar SINHA
2018-01-01
Feedback is said to exist in any amplifier when the fraction of output power in fed back as an input. Similarly, in gaseous discharge ions that incident on the cathode act as a natural feedback element to stabilize and self sustain the discharge. The present investigation is intended to emphasize the feedback nature of ions that emits secondary electrons (SEs) from the cathode surface in DC gas discharges. The average number of SEs emitted per incident ion and non ionic species (energetic neutrals, metastables and photons) which results from ion is defined as effective secondary electron emission coefficient (ESEEC,{γ }{{E}}). In this study, we derive an analytic expression that corroborates the relation between {γ }{{E}} and power influx by ion to the cathode based on the feedback theory of an amplifier. In addition, experimentally, we confirmed the typical positive feedback nature of SEE from the cathode in argon DC glow discharges. The experiment is done for three different cathode material of same dimension (tungsten (W), copper (Cu) and brass) under identical discharge conditions (pressure: 0.45 mbar, cathode bias: -600 V, discharge gab: 15 cm and operating gas: argon). Further, we found that the {γ }{{E}} value of these cathode material controls the amount of feedback power given by ions. The difference in feedback leads different final output i.e the power carried by ion at cathode ({P}{{i}}{\\prime }{| }{{C}}). The experimentally obtained value of {P}{{i}}{\\prime }{| }{{C}} is 4.28 W, 6.87 W and 9.26 W respectively for W, Cu and brass. In addition, the present investigation reveals that the amount of feedback power in a DC gas discharges not only affect the fraction of power fed back to the cathode but also the entire characteristics of the discharge.
Accelerating functional verification of an integrated circuit
Deindl, Michael; Ruedinger, Jeffrey Joseph; Zoellin, Christian G.
2015-10-27
Illustrative embodiments include a method, system, and computer program product for accelerating functional verification in simulation testing of an integrated circuit (IC). Using a processor and a memory, a serial operation is replaced with a direct register access operation, wherein the serial operation is configured to perform bit shifting operation using a register in a simulation of the IC. The serial operation is blocked from manipulating the register in the simulation of the IC. Using the register in the simulation of the IC, the direct register access operation is performed in place of the serial operation.
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…
Children's reasoning about evaluative feedback.
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'.
Quantum mechanics in noninertial reference frames: Relativistic accelerations and fictitious forces
DOE Office of Scientific and Technical Information (OSTI.GOV)
Klink, W.H., E-mail: william-klink@uiowa.edu; Wickramasekara, S., E-mail: wickrama@grinnell.edu
2016-06-15
One-particle systems in relativistically accelerating reference frames can be associated with a class of unitary representations of the group of arbitrary coordinate transformations, an extension of the Wigner–Bargmann definition of particles as the physical realization of unitary irreducible representations of the Poincaré group. Representations of the group of arbitrary coordinate transformations become necessary to define unitary operators implementing relativistic acceleration transformations in quantum theory because, unlike in the Galilean case, the relativistic acceleration transformations do not themselves form a group. The momentum operators that follow from these representations show how the fictitious forces in noninertial reference frames are generated inmore » quantum theory.« less
Quantum mechanics in noninertial reference frames: Relativistic accelerations and fictitious forces
NASA Astrophysics Data System (ADS)
Klink, W. H.; Wickramasekara, S.
2016-06-01
One-particle systems in relativistically accelerating reference frames can be associated with a class of unitary representations of the group of arbitrary coordinate transformations, an extension of the Wigner-Bargmann definition of particles as the physical realization of unitary irreducible representations of the Poincaré group. Representations of the group of arbitrary coordinate transformations become necessary to define unitary operators implementing relativistic acceleration transformations in quantum theory because, unlike in the Galilean case, the relativistic acceleration transformations do not themselves form a group. The momentum operators that follow from these representations show how the fictitious forces in noninertial reference frames are generated in quantum theory.
Kerr, Robert R; Grayden, David B; Thomas, Doreen A; Gilson, Matthieu; Burkitt, Anthony N
2014-01-01
The brain is able to flexibly select behaviors that adapt to both its environment and its present goals. This cognitive control is understood to occur within the hierarchy of the cortex and relies strongly on the prefrontal and premotor cortices, which sit at the top of this hierarchy. Pyramidal neurons, the principal neurons in the cortex, have been observed to exhibit much stronger responses when they receive inputs at their soma/basal dendrites that are coincident with inputs at their apical dendrites. This corresponds to inputs from both lower-order regions (feedforward) and higher-order regions (feedback), respectively. In addition to this, coherence between oscillations, such as gamma oscillations, in different neuronal groups has been proposed to modulate and route communication in the brain. In this paper, we develop a simple, but novel, neural mass model in which cortical units (or ensembles) exhibit gamma oscillations when they receive coherent oscillatory inputs from both feedforward and feedback connections. By forming these units into circuits that can perform logic operations, we identify the different ways in which operations can be initiated and manipulated by top-down feedback. We demonstrate that more sophisticated and flexible top-down control is possible when the gain of units is modulated by not only top-down feedback but by coherence between the activities of the oscillating units. With these types of units, it is possible to not only add units to, or remove units from, a higher-level unit's logic operation using top-down feedback, but also to modify the type of role that a unit plays in the operation. Finally, we explore how different network properties affect top-down control and processing in large networks. Based on this, we make predictions about the likely connectivities between certain brain regions that have been experimentally observed to be involved in goal-directed behavior and top-down attention.
Kerr, Robert R.; Grayden, David B.; Thomas, Doreen A.; Gilson, Matthieu; Burkitt, Anthony N.
2014-01-01
The brain is able to flexibly select behaviors that adapt to both its environment and its present goals. This cognitive control is understood to occur within the hierarchy of the cortex and relies strongly on the prefrontal and premotor cortices, which sit at the top of this hierarchy. Pyramidal neurons, the principal neurons in the cortex, have been observed to exhibit much stronger responses when they receive inputs at their soma/basal dendrites that are coincident with inputs at their apical dendrites. This corresponds to inputs from both lower-order regions (feedforward) and higher-order regions (feedback), respectively. In addition to this, coherence between oscillations, such as gamma oscillations, in different neuronal groups has been proposed to modulate and route communication in the brain. In this paper, we develop a simple, but novel, neural mass model in which cortical units (or ensembles) exhibit gamma oscillations when they receive coherent oscillatory inputs from both feedforward and feedback connections. By forming these units into circuits that can perform logic operations, we identify the different ways in which operations can be initiated and manipulated by top-down feedback. We demonstrate that more sophisticated and flexible top-down control is possible when the gain of units is modulated by not only top-down feedback but by coherence between the activities of the oscillating units. With these types of units, it is possible to not only add units to, or remove units from, a higher-level unit's logic operation using top-down feedback, but also to modify the type of role that a unit plays in the operation. Finally, we explore how different network properties affect top-down control and processing in large networks. Based on this, we make predictions about the likely connectivities between certain brain regions that have been experimentally observed to be involved in goal-directed behavior and top-down attention. PMID:25152715
Host behaviour–parasite feedback: an essential link between animal behaviour and disease ecology
Archie, Elizabeth A.; Craft, Meggan E.; Hawley, Dana M.; Martin, Lynn B.; Moore, Janice; White, Lauren
2016-01-01
Animal behaviour and the ecology and evolution of parasites are inextricably linked. For this reason, animal behaviourists and disease ecologists have been interested in the intersection of their respective fields for decades. Despite this interest, most research at the behaviour–disease interface focuses either on how host behaviour affects parasites or how parasites affect behaviour, with little overlap between the two. Yet, the majority of interactions between hosts and parasites are probably reciprocal, such that host behaviour feeds back on parasites and vice versa. Explicitly considering these feedbacks is essential for understanding the complex connections between animal behaviour and parasite ecology and evolution. To illustrate this point, we discuss how host behaviour–parasite feedbacks might operate and explore the consequences of feedback for studies of animal behaviour and parasites. For example, ignoring the feedback of host social structure on parasite dynamics can limit the accuracy of predictions about parasite spread. Likewise, considering feedback in studies of parasites and animal personalities may provide unique insight about the maintenance of variation in personality types. Finally, applying the feedback concept to links between host behaviour and beneficial, rather than pathogenic, microbes may shed new light on transitions between mutualism and parasitism. More generally, accounting for host behaviour–parasite feedbacks can help identify critical gaps in our understanding of how key host behaviours and parasite traits evolve and are maintained. PMID:27053751
Host behaviour-parasite feedback: an essential link between animal behaviour and disease ecology.
Ezenwa, Vanessa O; Archie, Elizabeth A; Craft, Meggan E; Hawley, Dana M; Martin, Lynn B; Moore, Janice; White, Lauren
2016-04-13
Animal behaviour and the ecology and evolution of parasites are inextricably linked. For this reason, animal behaviourists and disease ecologists have been interested in the intersection of their respective fields for decades. Despite this interest, most research at the behaviour-disease interface focuses either on how host behaviour affects parasites or how parasites affect behaviour, with little overlap between the two. Yet, the majority of interactions between hosts and parasites are probably reciprocal, such that host behaviour feeds back on parasites and vice versa. Explicitly considering these feedbacks is essential for understanding the complex connections between animal behaviour and parasite ecology and evolution. To illustrate this point, we discuss how host behaviour-parasite feedbacks might operate and explore the consequences of feedback for studies of animal behaviour and parasites. For example, ignoring the feedback of host social structure on parasite dynamics can limit the accuracy of predictions about parasite spread. Likewise, considering feedback in studies of parasites and animal personalities may provide unique insight about the maintenance of variation in personality types. Finally, applying the feedback concept to links between host behaviour and beneficial, rather than pathogenic, microbes may shed new light on transitions between mutualism and parasitism. More generally, accounting for host behaviour-parasite feedbacks can help identify critical gaps in our understanding of how key host behaviours and parasite traits evolve and are maintained. © 2016 The Author(s).
Sheard, Laura; Marsh, Claire; O'Hara, Jane; Armitage, Gerry; Wright, John; Lawton, Rebecca
2017-04-01
Patients are increasingly being asked for feedback about their healthcare experiences. However, healthcare staff often find it difficult to act on this feedback in order to make improvements to services. This paper draws upon notions of legitimacy and readiness to develop a conceptual framework (Patient Feedback Response Framework - PFRF) which outlines why staff may find it problematic to respond to patient feedback. A large qualitative study was conducted with 17 ward based teams between 2013 and 2014, across three hospital Trusts in the North of England. This was a process evaluation of a wider study where ward staff were encouraged to make action plans based on patient feedback. We focus on three methods here: i) examination of taped discussion between ward staff during action planning meetings ii) facilitators notes of these meetings iii) telephone interviews with staff focusing on whether action plans had been achieved six months later. Analysis employed an abductive approach. Through the development of the PFRF, we found that making changes based on patient feedback is a complex multi-tiered process and not something that ward staff can simply 'do'. First, staff must exhibit normative legitimacy - the belief that listening to patients is a worthwhile exercise. Second, structural legitimacy has to be in place - ward teams need adequate autonomy, ownership and resource to enact change. Some ward teams are able to make improvements within their immediate control and environment. Third, for those staff who require interdepartmental co-operation or high level assistance to achieve change, organisational readiness must exist at the level of the hospital otherwise improvement will rarely be enacted. Case studies drawn from our empirical data demonstrate the above. It is only when appropriate levels of individual and organisational capacity to change exist, that patient feedback is likely to be acted upon to improve services. Copyright © 2017 The Authors. Published
Fermilab proton accelerator complex status and improvement plans
DOE Office of Scientific and Technical Information (OSTI.GOV)
Shiltsev, Vladimir
2017-05-30
Fermilab carries out an extensive program of accelerator-based high energy particle physics research at the Intensity Frontier that relies on the operation of 8 GeV and 120 GeV proton beamlines for a n umber of fixed target experiments. Routine operation with a world-record 700kW of average 120 GeV beam power on the neutrino target was achieved in 2017 as the result of the Proton Improvement Plan (PIP) upgrade. There are plans to further increase the power to 900 – 1000 kW. The next major upgrade of the FNAL accelerator complex, called PIP-II, is under development. It aims at 1.2MW beammore » power on target at the start of the LBNF/DUNE experiment in the middle of the next decade and assumes replacement of the existing 40-years old 400 MeV normal-conducting Linac with a modern 800 MeV superconducting RF linear accelerator. There are several concepts to further double the beam power to >2.4MW after replacement of the existing 8 GeV Booster synchrotron. In this article we discuss current performance of the Fermilab proton accelerator complex, the upgrade plans for the next two decades and the accelerator R&D program to address cost and performance risks for these upgrades.« less
NASA Astrophysics Data System (ADS)
Kim, Jongwon; Son, Hyock-Jun; Park, Young-Ho
2017-11-01
The post-accelerator of isotope separation on-line (ISOL) system for rare isotope science project (RISP) is a superconducting linear accelerator (SC-linac) with a DC equivalent voltage of around 160 MV. An isotope beam extracted from the ISOL is in a charge state of 1+ and its charge state is increased to n+ by charge breeding with an electron beam ion source (EBIS). The charge breeding takes tens of ms and the pulse width of extracted beam from the EBIS is tens of μs, which operates at up to 30 Hz. Consequently a large portion of radio frequency (rf) time of the post SC-linac is unused. The post-linac is equipped also with an electron cyclotron resonance (ECR) ion source for stable ion acceleration. Thanks to the large phase acceptance of SC-linac, it is possible to accelerate simultaneously both stable and radioisotope ions with a similar charge to mass ratio by sharing rf time. This operation scheme is implemented for RISP with the addition of an electric chopper and magnetic kickers. The facility will be capable of providing the users of the ISOL and in-flight fragmentation (IF) systems with different beams simultaneously, which would help nuclear science users in obtaining a beam time as high-precision measurements often need long hours.
Surprising feedback improves later memory.
Fazio, Lisa K; Marsh, Elizabeth J
2009-02-01
The hypercorrection effect is the finding that high-confidence errors are more likely to be corrected after feedback than are low-confidence errors (Butterfield & Metcalfe, 2001). In two experiments, we explored the idea that the hypercorrection effect results from increased attention to surprising feedback. In Experiment 1, participants were more likely to remember the appearance of the presented feedback when the feedback did not match expectations. In Experiment 2, we replicated this effect using more distinctive sources and also demonstrated the hypercorrection effect in this modified paradigm. Overall, participants better remembered both the surface features and the content of surprising feedback.
Experimental signatures of direct-laser-acceleration-assisted laser wakefield acceleration
NASA Astrophysics Data System (ADS)
Shaw, J. L.; Lemos, N.; Marsh, K. A.; Froula, D. H.; Joshi, C.
2018-04-01
The direct laser acceleration (DLA) of electrons in a laser wakefield accelerator (LWFA) operating in the forced or quasi-blowout regimes has been investigated through experiment and simulation. When there is a significant overlap between the trapped electrons and the drive laser in a LWFA cavity, the resulting electrons can gain energy from both the LWFA and the DLA mechanisms. Experimental work investigates the properties of the electron beams produced in a LWFA with ionization injection by dispersing those beams in the direction perpendicular to the laser polarization. These electron beams show certain spectral features that are characteristic of DLA. These characteristic features are reproduced using particle-in-cell simulations, where particle tracking was used to elucidate the roles of LWFA and DLA to the energy gain of the electrons in this experimental regime and to demonstrate that such spectral features are definitive signatures of the presence of DLA in LWFA.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Bein, B. M.; Berkebile-Stoiser, S.; Veronig, A. M.
2012-08-10
Using high time cadence images from the STEREO EUVI, COR1, and COR2 instruments, we derived detailed kinematics of the main acceleration stage for a sample of 95 coronal mass ejections (CMEs) in comparison with associated flares and filament eruptions. We found that CMEs associated with flares reveal on average significantly higher peak accelerations and lower acceleration phase durations, initiation heights, and heights, at which they reach their peak velocities and peak accelerations. This means that CMEs that are associated with flares are characterized by higher and more impulsive accelerations and originate from lower in the corona where the magnetic fieldmore » is stronger. For CMEs that are associated with filament eruptions we found only for the CME peak acceleration significantly lower values than for events that were not associated with filament eruptions. The flare rise time was found to be positively correlated with the CME acceleration duration and negatively correlated with the CME peak acceleration. For the majority of the events the CME acceleration starts before the flare onset (for 75% of the events) and the CME acceleration ends after the soft X-ray (SXR) peak time (for 77% of the events). In {approx}60% of the events, the time difference between the peak time of the flare SXR flux derivative and the peak time of the CME acceleration is smaller than {+-}5 minutes, which hints at a feedback relationship between the CME acceleration and the energy release in the associated flare due to magnetic reconnection.« less
Moving Feedback Forward: Theory to Practice
ERIC Educational Resources Information Center
Orsmond, Paul; Maw, Stephen J.; Park, Julian R.; Gomez, Stephen; Crook, Anne C.
2013-01-01
There is substantial research interest in tutor feedback and students' perception and use of such feedback. This paper considers some of the major issues raised in relation to tutor feedback and student learning. We explore some of the current feedback drivers, most notably the need for feedback to move away from simply a monologue from a tutor to…
Research of the master-slave robot surgical system with the function of force feedback.
Shi, Yunyong; Zhou, Chaozheng; Xie, Le; Chen, Yongjun; Jiang, Jun; Zhang, Zhenfeng; Deng, Ze
2017-12-01
Surgical robots lack force feedback, which may lead to operation errors. In order to improve surgical outcomes, this research developed a new master-slave surgical robot, which was designed with an integrated force sensor. The new structure designed for the master-slave robot employs a force feedback mechanism. A six-dimensional force sensor was mounted on the tip of the slave robot's actuator. Sliding model control was adopted to control the slave robot. According to the movement of the master system manipulated by the surgeon, the slave's movement and the force feedback function were validated. The motion was completed, the standard deviation was calculated, and the force data were detected. Hence, force feedback was realized in the experiment. The surgical robot can help surgeons to complete trajectory motions with haptic sensation. Copyright © 2017 John Wiley & Sons, Ltd.
Experimental Results from a Resonant Dielectric Laser Accelerator
NASA Astrophysics Data System (ADS)
Yoder, Rodney; McNeur, Joshua; Sozer, Esin; Travish, Gil; Hazra, Kiran Shankar; Matthews, Brian; England, Joel; Peralta, Edgar; Wu, Ziran
2015-04-01
Laser-powered accelerators have the potential to operate with very large accelerating gradients (~ GV/m) and represent a path toward extremely compact colliders and accelerator technology. Optical-scale laser-powered devices based on field-shaping structures (known as dielectric laser accelerators, or DLAs) have been described and demonstrated recently. Here we report on the first experimental results from the Micro-Accelerator Platform (MAP), a DLA based on a slab-symmetric resonant optical-scale structure. As a resonant (rather than near-field) device, the MAP is distinct from other DLAs. Its cavity resonance enhances its accelerating field relative to the incoming laser fields, which are coupled efficiently through a diffractive optic on the upper face of the device. The MAP demonstrated modest accelerating gradients in recent experiments, in which it was powered by a Ti:Sapphire laser well below its breakdown limit. More detailed results and some implications for future developments will be discussed. Supported in part by the U.S. Defense Threat Reduction Agency (UCLA); U.S. Dept of Energy (SLAC); and DARPA (SLAC).
Effects of Type and Strength of Force Feedback on Movement Time in a Target Selection Task
NASA Technical Reports Server (NTRS)
Rorie, Robert Conrad; Vu, Kim-Phuong L.; Marayong, Panadda; Robles, Jose; Strybel, Thomas Z.; Battiste, Vernol
2013-01-01
Future cockpits will likely include new onboard technologies, such as cockpit displays of traffic information, to help support future flight deck roles and responsibilities. These new technologies may benefit from multimodal feedback to aid pilot information processing. The current study investigated the effects of multiple levels of force feedback on operator performance in an aviation task. Participants were presented with two different types of force feedback (gravitational and spring force feedback) for a discrete targeting task, with multiple levels of gain examined for each force feedback type. Approach time and time in target were recorded. Results suggested that the two highest levels of gravitational force significantly reduced approach times relative to the lowest level of gravitational force. Spring force level only affected time in target. Implications of these findings for the design of future cockpit displays will be discussed.
DOE Office of Scientific and Technical Information (OSTI.GOV)
None, None
Over a full two day period, February 2–3, 2016, the Office of High Energy Physics convened a workshop in Gaithersburg, MD to seek community input on development of an Advanced Accelerator Concepts (AAC) research roadmap. The workshop was in response to a recommendation by the HEPAP Accelerator R&D Subpanel [1] [2] to “convene the university and laboratory proponents of advanced acceleration concepts to develop R&D roadmaps with a series of milestones and common down selection criteria towards the goal for constructing a multi-TeV e+e– collider” (the charge to the workshop can be found in Appendix A). During the workshop, proponentsmore » of laser-driven plasma wakefield acceleration (LWFA), particle-beam-driven plasma wakefield acceleration (PWFA), and dielectric wakefield acceleration (DWFA), along with a limited number of invited university and laboratory experts, presented and critically discussed individual concept roadmaps. The roadmap workshop was preceded by several preparatory workshops. The first day of the workshop featured presentation of three initial individual roadmaps with ample time for discussion. The individual roadmaps covered a time period extending until roughly 2040, with the end date assumed to be roughly appropriate for initial operation of a multi-TeV e+e– collider. The second day of the workshop comprised talks on synergies between the roadmaps and with global efforts, potential early applications, diagnostics needs, simulation needs, and beam issues and challenges related to a collider. During the last half of the day the roadmaps were revisited but with emphasis on the next five to ten years (as specifically requested in the charge) and on common challenges. The workshop concluded with critical and unanimous endorsement of the individual roadmaps and an extended discussion on the characteristics of the common challenges. (For the agenda and list of participants see Appendix B.)« less
Improving Written Communication Through Minimal Feedback
Traxler, Matthew J.; Gernsbacher, Morton Ann
2014-01-01
We propose that writers must form accurate representations of how their readers will interpret their texts to convey their ideas successfully. In two experiments, we investigated whether getting feedback from their readers helps writers form better representations of how their texts are interpreted. In our first experiment, one group of subjects (writers) wrote descriptions of a set of geometric figures; another group of subjects (readers) read those descriptions and used them to select the figures from sets of similar looking distractor figures. Half the writers received feedback on how well their readers selected the figures, and half the writers did not receive this feedback. Those writers who received feedback improved their descriptions more than those writers who did not receive feedback. In our second experiment, half the writers received two treatments of feedback on their descriptions of one set of figures, whereas the other half of the writers did not receive feedback. Then, all the writers described a new set of figures. Those writers who had previously received feedback wrote better new descriptions than did those writers who had never received feedback. We concluded that feedback – even this minimal form of feedback – helps writers to envision how readers interpret their texts. PMID:25520535
Teunissen, Pim W; Stapel, Diederik A; van der Vleuten, Cees; Scherpbier, Albert; Boor, Klarke; Scheele, Fedde
2009-07-01
The literature on feedback in clinical medical education has predominantly treated trainees as passive recipients. Past research has focused on how clinical supervisors can use feedback to improve a trainee's performance. On the basis of research in social and organizational psychology, the authors reconceptualized residents as active seekers of feedback. They investigated what individual and situational variables influence residents' feedback-seeking behavior on night shifts. Early in 2008, the authors sent obstetrics-gynecology residents in the Netherlands--both those in their first two years of graduate training and those gaining experience between undergraduate and graduate training--a questionnaire that assessed four predictor variables (learning and performance goal orientation, and instrumental and supportive leadership), two mediator variables (perceived feedback benefits and costs), and two outcome variables (frequency of feedback inquiry and monitoring). They used structural equation modeling software to test a hypothesized model of relationships between variables. The response rate was 76.5%. Results showed that residents who perceive more feedback benefits report a higher frequency of feedback inquiry and monitoring. More perceived feedback costs result mainly in more feedback monitoring. Residents with a higher learning goal orientation perceive more feedback benefits and fewer costs. Residents with a higher performance goal orientation perceive more feedback costs. Supportive physicians lead residents to perceive more feedback benefits and fewer costs. This study showed that some residents actively seek feedback. Residents' feedback-seeking behavior partially depends on attending physicians' supervisory style. Residents' goal orientations influence their perceptions of the benefits and costs of feedback-seeking.
Response to reflected-force feedback to fingers in teleoperations
NASA Technical Reports Server (NTRS)
Sutter, P. H.; Iatridis, J. C.; Thakor, N. V.
1989-01-01
Reflected-force feedback is an important aspect of teleoperations. The objective is to determine the ability of the human operator to respond to that force. Telerobotics operation is simulated by computer control of a motor-driven device with capabilities for programmable force feedback and force measurement. A computer-controlled motor drive is developed that provides forces against the fingers as well as (angular) position control. A load cell moves in a circular arc as it is pushed by a finger and measures reaction forces on the finger. The force exerted by the finger on the load cell and the angular position are digitized and recorded as a function of time by the computer. Flexure forces of the index, long and ring fingers of the human hand in opposition to the motor driven load cell are investigated. Results of the following experiments are presented: (1) Exertion of maximum finger force as a function of angle; (2) Exertion of target finger force against a computer controlled force; and (3) Test of the ability to move to a target force against a force that is a function of position. Averaged over ten individuals, the maximum force that could be exerted by the index or long finger is about 50 Newtons, while that of the ring finger is about 40 Newtons. From the tests of the ability of a subject to exert a target force, it was concluded that reflected-force feedback can be achieved with the direct kinesthetic perception of force without the use of tactile or visual clues.
Nonlinear feedback method of robot control - A preliminary experimental study
NASA Technical Reports Server (NTRS)
Tarn, T. J.; Ganguly, S.; Li, Z.; Bejczy, A. K.
1990-01-01
The nonlinear feedback method of robot control has been experimentally implemented on two PUMA 560 robot arms. The feasibility of the proposed controller, which was shown viable through simulation results earlier, is stressed. The servomechanism operates in task space, and the nonlinear feedback takes care of the necessary transformations to compute the necessary joint currents. A discussion is presented of the implementation with details of the experiments performed. The performance of the controller is encouraging but was limited to 100-Hz sampling frequency and to derived velocity information at the time of the experimentation. The setup of the lab, the software aspects, results, and the control hardware architecture that has recently been implemented are discussed.
Brink, Adrian J; Messina, Angeliki P; Feldman, Charles; Richards, Guy A; van den Bergh, Dena
2017-04-01
Few data exist on the implementation of process measures to facilitate adherence to peri-operative antibiotic prophylaxis (PAP) guidelines in Africa. To implement an improvement model for PAP utilizing existing resources, in order to achieve a reduction in surgical site infections (SSIs) across a heterogeneous group of 34 urban and rural South African hospitals. A pharmacist-driven, prospective audit and feedback strategy involving change management and improvement principles was utilized. This 2.5 year intervention involved a pre-implementation phase to test a PAP guideline and a 'toolkit' at pilot sites. Following antimicrobial stewardship committee and clinician endorsement, the model was introduced in all institutions and a survey of baseline SSI and compliance rates with four process measures (antibiotic choice, dose, administration time and duration) was performed. The post-implementation phase involved audit, intervention and monthly feedback to facilitate improvements in compliance. For 70 weeks of standardized measurements and feedback, 24 206 surgical cases were reviewed. There was a significant improvement in compliance with all process measures (composite compliance) from 66.8% (95% CI 64.8-68.7) to 83.3% (95% CI 80.8-85.8), representing a 24.7% increase ( P < 0.0001). The SSI rate decreased by 19.7% from a mean group rate of 2.46 (95% CI 2.18-2.73) pre-intervention to 1.97 post-intervention (95% CI 1.79-2.15) ( P = 0.0029). The implementation of process improvement initiatives and principles targeted to institutional needs utilizing pharmacists can effectively improve PAP guideline compliance and sustainable patient outcomes. © The Author 2016. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
Nataraj, Raviraj; Audu, Musa L.; Triolo, Ronald J.
2017-01-01
This paper reviews the field of feedback control for neuroprosthesis systems that restore advanced standing function to individuals with spinal cord injury. Investigations into closed-loop control of standing by functional neuromuscular stimulation (FNS) have spanned three decades. The ultimate goal for FNS standing control systems is to facilitate hands free standing and enabling the user to perform manual functions at self-selected leaning positions. However, most clinical systems for home usage currently only provide basic upright standing using preprogrammed stimulation patterns. To date, online modulation of stimulation to produce advanced standing functions such as balance against postural disturbances or the ability to assume leaning postures have been limited to simulation and laboratory investigations. While great technological advances have been made in biomechanical sensing and interfaces for neuromuscular stimulation, further progress is still required for finer motor control by FNS. Another major challenge is the development of sophisticated control schemes that produce the necessary postural adjustments, adapt against accelerating muscle fatigue, and consider volitional actions of the intact upper-body of the user. Model-based development for novel control schemes are proven and sensible approaches to prototype and test the basic operating efficacy of potentially complex and multi-faceted control systems. The major considerations for further innovation of such systems are summarized in this paper prior to describing the evolution of closed-loop FNS control of standing from previous works. Finally, necessary emerging technologies to for implementing FNS feedback control systems for standing are identified. These technological advancements include novel electrodes that more completely and selectively activate paralyzed musculature and implantable sensors and stimulation modules for flexible neuroprosthesis system deployment. PMID:28215399
Finite element analyses of a linear-accelerator electron gun
DOE Office of Scientific and Technical Information (OSTI.GOV)
Iqbal, M., E-mail: muniqbal.chep@pu.edu.pk, E-mail: muniqbal@ihep.ac.cn; Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049; Wasy, A.
Thermo-structural analyses of the Beijing Electron-Positron Collider (BEPCII) linear-accelerator, electron gun, were performed for the gun operating with the cathode at 1000 °C. The gun was modeled in computer aided three-dimensional interactive application for finite element analyses through ANSYS workbench. This was followed by simulations using the SLAC electron beam trajectory program EGUN for beam optics analyses. The simulations were compared with experimental results of the assembly to verify its beam parameters under the same boundary conditions. Simulation and test results were found to be in good agreement and hence confirmed the design parameters under the defined operating temperature. The gunmore » is operating continuously since commissioning without any thermal induced failures for the BEPCII linear accelerator.« less
Finite element analyses of a linear-accelerator electron gun
NASA Astrophysics Data System (ADS)
Iqbal, M.; Wasy, A.; Islam, G. U.; Zhou, Z.
2014-02-01
Thermo-structural analyses of the Beijing Electron-Positron Collider (BEPCII) linear-accelerator, electron gun, were performed for the gun operating with the cathode at 1000 °C. The gun was modeled in computer aided three-dimensional interactive application for finite element analyses through ANSYS workbench. This was followed by simulations using the SLAC electron beam trajectory program EGUN for beam optics analyses. The simulations were compared with experimental results of the assembly to verify its beam parameters under the same boundary conditions. Simulation and test results were found to be in good agreement and hence confirmed the design parameters under the defined operating temperature. The gun is operating continuously since commissioning without any thermal induced failures for the BEPCII linear accelerator.
Finite element analyses of a linear-accelerator electron gun.
Iqbal, M; Wasy, A; Islam, G U; Zhou, Z
2014-02-01
Thermo-structural analyses of the Beijing Electron-Positron Collider (BEPCII) linear-accelerator, electron gun, were performed for the gun operating with the cathode at 1000 °C. The gun was modeled in computer aided three-dimensional interactive application for finite element analyses through ANSYS workbench. This was followed by simulations using the SLAC electron beam trajectory program EGUN for beam optics analyses. The simulations were compared with experimental results of the assembly to verify its beam parameters under the same boundary conditions. Simulation and test results were found to be in good agreement and hence confirmed the design parameters under the defined operating temperature. The gun is operating continuously since commissioning without any thermal induced failures for the BEPCII linear accelerator.
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…