elektronika: Positive feedback

Evidence: 100 • authority: 72

Positive feedback (exacerbating feedback, self-reinforcing feedback) is a process that occurs in a feedback loop where the outcome of a process reinforces the inciting process to build momentum. As such, these forces can exacerbate the effects of a small disturbance. That is, the effects of a perturbation on a system include an increase in the magnitude of the perturbation. That is, A produces more of B which in turn produces more of A. In contrast, a system in which the results of a change act to reduce or counteract it has negative feedback. Both concepts play an important role in science and engineering, including biology, chemistry, and cybernetics. Mathematically, positive feedback is…

Evidence: 53 • authority: 88

Positive feedback loops exacerbate the influence of superspreaders in disease transmission. Abstract Superspreaders are recognised as being important drivers of disease spread, most recently having played a major role in the ongoing COVID-19 pandemic. However, models to date have assumed random occurrence of superspreaders, irrespective of whom they were infected by. Evidence suggests though that this may not be the case, and that those individuals infected by superspreaders may be more likely to become superspreaders themselves, hence creating a positive feedback loop. This could happen, for example, through superspreaders releasing high infective doses that cause high infection intensitie…

Evidence: 53 • authority: 92

Haemorrhage, hypercoagulability and ischaemia: Evolution of brain injury after aneurysmal subarachnoid haemorrhage.. Aneurysmal subarachnoid haemorrhage (aSAH) is a catastrophic cerebrovascular event associated with high early mortality and substantial long-term disability. Delayed cerebral ischaemia (DCI) is among its most severe complications and a principal driver of secondary neurological injury. Despite decades of research describing diverse pathophysiological mechanisms, a unifying framework for DCI pathogenesis is still lacking, and its clinical prediction remains challenging. We therefore conducted a narrative review to synthesise current understanding of the spatiotemporal evolutio…

Evidence: 53 • authority: 72

Environmental degradation is the deterioration of the environment through depletion of resources such as quality of air, water and soil; the destruction of ecosystems; habitat destruction; the extinction of wildlife; and pollution. It is defined as any change or disturbance to the environment perceived to be deleterious or undesirable. The environmental degradation process amplifies the impact of environmental issues which leave lasting impacts on the environment. Environmental degradation is one of the ten threats officially cautioned by the High-level Panel on Threats, Challenges and Change of the United Nations. The United Nations International Strategy for Disaster Reduction defines env…

Evidence: — • authority: 72

In electronics, noise is an unwanted disturbance in an electrical signal. Noise generated by electronic devices varies greatly as it is produced by several different effects. In particular, noise is inherent in physics and central to thermodynamics. Any conductor with electrical resistance will generate thermal noise inherently. The final elimination of thermal noise in electronics can only be achieved cryogenically, and even then quantum noise would remain inherent. Electronic noise is a common component of noise in signal processing. In communication systems, noise is an error or undesired random disturbance of a useful information signal in a communication channel. The noise is a summati…

Evidence: — • authority: 72

A wildfire, forest fire, brushfire or a bushfire is an unplanned and uncontrolled fire in an area of combustible vegetation. Some natural forest ecosystems depend on wildfire. Modern forest management often engages in prescribed burns to mitigate fire risk and promote natural forest cycles. Controlled burns can turn into wildfires if they escape containment lines. Wildfires can be classified by cause of ignition, physical properties, combustible material present, and the effect of weather on the fire. Wildfire severity results from a combination of factors such as available fuels, physical setting, and weather. Climatic cycles with wet periods that create substantial fuels, followed by drou…

Evidence: — • authority: 88

Output Feedback Control of Overhead Cranes Based on Disturbance Compensation. In practice, various factors such as friction, unmodeled dynamics and uncertain external disturbances often affect overhead cranes. The existing crane control methods often neglect these factors or address these factors by robust techniques. Moreover, most of them do not take input saturation into account and require full-state feedback. In this paper, taking the practical issues of uncertain disturbances, input saturation and output feedback into account, we propose an input-saturated output feedback control strategy for the underactuated two-dimensional (2-D) overhead crane systems with uncertain disturbances. S…