Study of the Impact of Negative Feedback on Frequency Responses of Small-signal Multistage Amplifiers

2020 ◽  
Author(s):  
Ivo Dochev ◽  
Stoycho Manev ◽  
Lilyana Docheva
Keyword(s):  
Negative Feedback ◽  
Small Signal ◽  
Frequency Responses ◽  
Multistage Amplifiers ◽  
The Impact

scholarly journals Self-esteem and social support in the occupational stress-subjective health relationship among medical professionals

2009 ◽  
Vol 40 (1) ◽  
pp. 13-19 ◽  
Author(s):  
Tadeusz Ostrowski
Keyword(s):  
Social Support ◽  
Occupational Stress ◽  
Job Stress ◽  
Negative Feedback ◽  
Feedback Loop ◽  
Self Esteem ◽  
Subjective Health ◽  
Medical Professionals ◽  
Negative Feedback Loop ◽  
The Impact

Self-esteem and social support in the occupational stress-subjective health relationship among medical professionals The starting point for the presented study was the concept by House who construed social support as buffering the impact of work-related stress on health. Self-esteem was taken under consideration as the other potential stress buffer. It was hypothesized that both social support and self-esteem would have a salutogenic effect, since they attenuate the experience of occupational stress and reduce health problems associated with the experienced job stress. Participants in the study were 361 medical professionals representing various specialties. They were examined using the Subjective Job Evaluation Questionnaire by Dudek et al., the Mood and Health State Questionnaire by Rząsa, the Self-Esteem Scale by M. Rosenberg and Significant Other Scale by Power et al. The higher was the respondents' occupational stress, the poorer was their subjective physical health. Such components of occupational stress as responsibility, psychological strain due to job complexity, lack of rewards at work, and a sense of threat were found to be most important in this respect. These four components of occupational stress were interrelated and constituted a feedback loop. The study confirmed a salutogenic role of self-esteem, contributing to subjective health improvement. Satisfaction with social support had also a positive role, since it reduced the amount of experienced job stress, thus exerting a health-promoting effect. There was a direct negative feedback loop between self-esteem and somatic health problems. Irrespective of that, satisfaction with social support was found to interact with perceived occupational stress in a negative feedback loop. However, neither of these two factors, i.e. self-esteem and social support, had an effect of buffering the impact of occupational stress on health. This suggests that the initial model proposed by House as well as the present author's earlier research findings obtained from a smaller sample should be revised.

Oxytocin-induced facilitation of learning in a probabilistic task is associated with reduced feedback- and error-related negativity potentials

2020 ◽  
Vol 35 (1) ◽  
pp. 40-49
Author(s):  
Qian Zhuang ◽  
Siyu Zhu ◽  
Xue Yang ◽  
Xinqi Zhou ◽  
Xiaolei Xu ◽  
...  
Keyword(s):  
Negative Feedback ◽  
Early Stage ◽  
Conflict Detection ◽  
Social Feedback ◽  
Double Blind ◽  
Subsequent Performance ◽  
Error Awareness ◽  
Error Related Negativity ◽  
Positive And Negative Feedback ◽  
The Impact

Background: Feedback evaluation of actions and error response detection are critical for optimizing behavioral adaptation. Oxytocin can facilitate learning following social feedback but whether its effects vary as a function of feedback valence remains unclear. Aims: The present study aimed to investigate whether oxytocin would influence responses to positive and negative feedback differentially or equivalently. Methods: The present study employed a randomized, double-blind, placebo controlled within-subject design to investigate whether intranasal oxytocin (24 IU) influenced behavioral and evoked electrophysiological potential responses to positive or negative feedback in a probabilistic learning task. Results: Results showed that oxytocin facilitated learning and this effect was maintained in the absence of feedback. Using novel stimulus pairings, we found that oxytocin abolished bias towards learning more from negative feedback under placebo by increasing accuracy for positively reinforced stimuli. Oxytocin also decreased the feedback-related negativity difference (negative minus positive feedback) during learning, further suggesting that it rendered the evaluation of positive and negative feedback more equivalent. Additionally, post-learning oxytocin attenuated error-related negativity amplitudes but increased the late error positivity, suggesting that it may lower conflict detection between actual errors and expected correct responses at an early stage of processing but at a later stage increase error awareness and motivation for avoiding them. Conclusions: Oxytocin facilitates learning and subsequent performance by rendering the impact of positive relative to negative feedback more equivalent and also by reducing conflict detection and increasing error awareness, which may be beneficial for behavioral adaption.

scholarly journals Impedance Aggregation Method of Multiple Wind Turbines and Accuracy Analysis

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2035 ◽  
Author(s):  
Liang Chen ◽  
Heng Nian ◽  
Yunyang Xu
Keyword(s):  
Stability Analysis ◽  
Reference Frame ◽  
Wind Turbines ◽  
Power Distribution ◽  
Wind Farm ◽  
System Level ◽  
Small Signal ◽  
Impedance Model ◽  
The Stability ◽  
The Impact

The sequence domain impedance modeling of wind turbines (WTs) has been widely used in the stability analysis between WTs and weak grids with high line impedance. An aggregated impedance model of the wind farm is required in the system-level analysis. However, directly aggregating WT small-signal impedance models will lead to an inaccurate aggregated impedance model due to the mismatch of reference frame definitions among different WT subsystems, which may lead to inaccuracy in the stability analysis. In this paper, we analyze the impacts of the reference frame mismatch between a local small-signal impedance model and a global one on the accuracy of aggregated impedance and the accuracy of impedance-based stability analysis. The results revealed that the impact is related to the power distribution of the studied network. It was found that that the influence of mismatch on stability analysis became subtle when subsystems were balanced loaded. Considering that balanced loading is a common configuration of the practical application, direct impedance aggregation by local small-signal models can be applied due to its acceptable accuracy.

scholarly journals Assessing the Impact of DFIG Synthetic Inertia Provision on Power System Small-Signal Stability

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3440 ◽  
Author(s):  
Edgar Lucas ◽  
David Campos-Gaona ◽  
Olimpo Anaya-Lara
Keyword(s):  
Power System ◽  
Large Scale ◽  
Damping Ratio ◽  
System Stability ◽  
Electrical Network ◽  
Small Signal ◽  
Small Signal Stability ◽  
Signal Stability ◽  
Electromechanical Modes ◽  
The Impact

Synthetic inertia provision through the control of doubly-fed induction generator (DFIG) wind turbines is an effective means of providing frequency support to the wider electrical network. There are numerous control topologies to achieve this, many of which work by making modifications to the DFIG power controller and introducing additional loops to relate active power to electrical frequency. How these many controller designs compare to one-another in terms of their contribution to frequency response is a much studied topic, but perhaps less studied is their effect on the small-signal stability of the system. The concept of small-signal stability in the context of a power system is the ability to maintain synchronism when subjected to small disturbances, such as those associated with a change in load or a loss of generation. Amendments made to the control system of a large-scale wind farm will inevitably have an effect on the system as a whole, and by making a DFIG wind turbine behave more like a synchronous generator, which synthetic inertia provision does, may incur consequences relating to electromechanical oscillations between generating units. This work compares the implications of two prominent synthetic inertia controllers of varying complexity and their effect on small-signal stability. Eigenvalue analysis is conducted to highlight the key information relating to electromechanical modes between generators for the two control strategies, with a focus on how these affect the damping ratios. It is shown that as the synthetic inertia controller becomes both more complex and more effective, the damping ratio of the electromechanical modes is reduced, signifying a decreased system stability.

Impact of Large-Scale Integrated Wind Farms on the Small Signal Stability of Power System

2013 ◽  
Vol 805-806 ◽  
pp. 393-396
Author(s):  
Zhen Yu Xu ◽  
Zhen Qiao ◽  
Qian He ◽  
Xu Zhang ◽  
Jing Qi Su
Keyword(s):  
Power System ◽  
Large Scale ◽  
Power Grid ◽  
Wind Farms ◽  
Small Signal ◽  
Small Signal Stability ◽  
Direct Drive ◽  
Signal Model ◽  
Signal Stability ◽  
The Impact

With the penetration of wind energy is becoming higher and higher in power grid, it is very important to investigate the impact of wind generations on small signal stability. In this paper, a complete small signal model of wind turbine with direct-drive permanent magnet generator is built to study the impact of large-scale wind farms on the small signal stability of power system. By means of simulation and eigenvalue analysis, an actual power system is investigated, and the damping characteristic of power grid under different wind power penetration is discussed.

scholarly journals The Shape of Things to Come: Why Is Climate Change So Predictable?

2009 ◽  
Vol 22 (17) ◽  
pp. 4574-4589 ◽  
Author(s):  
Marcia B. Baker ◽  
Gerard H. Roe
Keyword(s):  
Climate Change ◽  
Probability Distribution ◽  
Climate Sensitivity ◽  
Negative Feedback ◽  
Temperature Response ◽  
Global Scale ◽  
Climate Forcing ◽  
Climate Projections ◽  
Ocean Heat Uptake ◽  
The Impact

Abstract The framework of feedback analysis is used to explore the controls on the shape of the probability distribution of global mean surface temperature response to climate forcing. It is shown that ocean heat uptake, which delays and damps the temperature rise, can be represented as a transient negative feedback. This transient negative feedback causes the transient climate change to have a narrower probability distribution than that of the equilibrium climate response (the climate sensitivity). In this sense, climate change is much more predictable than climate sensitivity. The width of the distribution grows gradually over time, a consequence of which is that the larger the climate change being contemplated, the greater the uncertainty is about when that change will be realized. Another consequence of this slow growth is that further efforts to constrain climate sensitivity will be of very limited value for climate projections on societally relevant time scales. Finally, it is demonstrated that the effect on climate predictability of reducing uncertainty in the atmospheric feedbacks is greater than the effect of reducing uncertainty in ocean feedbacks by the same proportion. However, at least at the global scale, the total impact of uncertainty in climate feedbacks is dwarfed by the impact of uncertainty in climate forcing, which in turn is contingent on choices made about future anthropogenic emissions.

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