 Evon Ypy , twenty-one this year, and is currently pursuing a (BA) Hons Degree in Interactive Media Design at The One Academy Sunway, Malaysia. A girl who loves to read Chinese fiction novels alot, to her, books are the visual to the mind. She is also a big fans of anime and manga, and is taking a part-time Japanese Language Level 2 classes in Ringo Language center. Besides, the results of her MBTI test shows that she is an INFJ who likes to think to talk, this is why she isn't a fast thinker, can't responses to question immediately, it often takes some buffering and loading times... If it scares you, it might be a good thing to try. |
❥ 1. Feedback loop
 2012年6月10日星期日  01:22  0 Comment(s)Definition of feedback?
Webster's (2001) define feedback as "a process in which the factors that produce a result are themselves modified, corrected, strengthened, etc. by that result" and "a response, as one that sets such a process in motion" (p.520).
Taken from : http://www.aect.org/edtech/29.pdf
What is feedback?
In a system where a transformation occurs, there are inputs and outputs. The inputs are the result of the environment's influence on the system, and the outputs are the influence of the system on the environment. Input and output are separated by a duration of time, as in before and after, or past and present.
Taken from: http://pespmc1.vub.ac.be/FEEDBACK.html
Types of feedback
It is divided into two types, usually termed positive and negative.
Positive feedback
A positive connection is one in which a change (increase or decrease) in some variable results in the same type of change (increase of decrease) in a second variable. The image 1 shows the positive connection for a cooling coffee cup implies that the hotter the coffee is the faster it cools. And the variables Tc and Tr are representing the coffee and the room temperature.
Negative feedback
A negative connection is one in which a change (increase or decrease) in some variable results in the opposite change (decrease or increase) in a second variable. As shows in image 2, a cooling coffee cup implies a positive cooling rate makes the coffee temperature drops.
Taken from : http://serc.carleton.edu/introgeo/models/loops.html
How a feedback loops work?
Examples of feedback loop on global warming
First example
In climate change, a feedback loop is the equivalent of a vicious or virtuous circle – something that accelerates or decelerates a warming trend. A positive feedback accelerates a temperature rise, whereas a negative feedback decelerates it.
Scientists are aware of a number of positive feedbacks loops in the climate system. One example is melting ice. Because ice is light-coloured and reflective, a large proportion of the sunlight that hits it is bounced back to space, which limits the amount of warming it causes. But as the world gets hotter, ice melts, revealing the darker-coloured land or water below. The result is that more of the sun's energy is absorbed, leading to more warming, which in turn leads to more ice melting – and so on.
Second example
Scientists say the warm weather adds to global warming because of "feedback loops."
In a feedback loop, the rising temperature on the Earth changes the environment in ways that then create even more heat. Scientists consider feedback loops the single-biggest threat to civilization from global warming.
Past a certain point -- the tipping point, they say -- there may be no stopping the changes.
Scientists working in the Arctic report that feedback loops are already under way. As the frozen sea surface of the Arctic Ocean melts back, there's less white to reflect the sun's heat back into space -- and more dark, open water to absorb that heat, which then melts the floating sea ice even faster. More than a third of summer sea ice disappeared in the past 30 years.
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