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  2. Exponential growth - Wikipedia

    en.wikipedia.org/wiki/Exponential_growth

    For any fixed b not equal to 1 (e.g. e or 2), the growth rate is given by the non-zero time τ. For any non-zero time τ the growth rate is given by the dimensionless positive number b. Thus the law of exponential growth can be written in different but mathematically equivalent forms, by using a different base.

  3. Malthusian growth model - Wikipedia

    en.wikipedia.org/wiki/Malthusian_growth_model

    r = the population growth rate, which Ronald Fisher called the Malthusian parameter of population growth in The Genetical Theory of Natural Selection, [2] and Alfred J. Lotka called the intrinsic rate of increase, [3] [4] t = time. The model can also be written in the form of a differential equation: =

  4. Doubling time - Wikipedia

    en.wikipedia.org/wiki/Doubling_time

    The doubling time is a characteristic unit (a natural unit of scale) for the exponential growth equation, and its converse for exponential decay is the half-life. As an example, Canada's net population growth was 2.7 percent in the year 2022, dividing 72 by 2.7 gives an approximate doubling time of about 27 years.

  5. Deal–Grove model - Wikipedia

    en.wikipedia.org/wiki/Deal–Grove_model

    Taking the short and long time limits of the above equation reveals two main modes of operation. The first mode, where the growth is linear, occurs initially when + is small. The second mode gives a quadratic growth and occurs when the oxide thickens as the oxidation time increases.

  6. Population dynamics - Wikipedia

    en.wikipedia.org/wiki/Population_dynamics

    We obtain: + = (+). This equation means that the sequence (N t) is geometric with first term N 0 and common ratio 1 + R, which we define to be λ. λ is also called the finite rate of increase. Therefore, by induction , we obtain the expression of the population size at time t : N t = λ t N 0 {\displaystyle N_{t}=\lambda ^{t}N_{0}} where λ t ...

  7. Entropy as an arrow of time - Wikipedia

    en.wikipedia.org/wiki/Entropy_as_an_arrow_of_time

    Therefore, the thermodynamic entropy, which is proportional to the marginal entropy, must also increase with time [8] (note that "not too long" in this context is relative to the time needed, in a classical version of the system, for it to pass through all its possible microstates—a time that can be roughly estimated as , where is the time ...

  8. Half-life - Wikipedia

    en.wikipedia.org/wiki/Half-life

    Half-life (symbol t ½) is the time required for a quantity (of substance) to reduce to half of its initial value.The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive.

  9. Ergodic hypothesis - Wikipedia

    en.wikipedia.org/wiki/Ergodic_hypothesis

    In physics and thermodynamics, the ergodic hypothesis [1] says that, over long periods of time, the time spent by a system in some region of the phase space of microstates with the same energy is proportional to the volume of this region, i.e., that all accessible microstates are equiprobable over a long period of time.