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chemistry (mass of one atom divided by the atomic mass constant, 1 Da) Bodenstein number: Bo or Bd = / = Max Bodenstein: chemistry (residence-time distribution; similar to the axial mass transfer Peclet number) [2] Damköhler numbers: Da =
In science, e-folding is the time interval in which an exponentially growing quantity increases or decreases by a factor of e; [1] it is the base-e analog of doubling time. This term is often used in many areas of science, such as in atmospheric chemistry , medicine , theoretical physics , and cosmology .
All other electric and magnetic units are derived from these four base units using the most basic common definitions: for example, electric charge q is defined as current I multiplied by time t, =, resulting in the unit of electric charge, the coulomb (C), being defined as 1 C = 1 A⋅s.
It is the first time-integral of the displacement [3] [4] (i.e. absement is the area under a displacement vs. time graph), so the displacement is the rate of change (first time-derivative) of the absement. The dimension of absement is length multiplied by time.
= where is the relaxation time of the particle (the time constant in the exponential decay of the particle velocity due to drag), is the fluid velocity of the flow well away from the obstacle, and is the characteristic dimension of the obstacle (typically its diameter) or a characteristic length scale in the flow (like boundary layer thickness ...
Imaginary time is a mathematical representation of time that appears in some approaches to special relativity and quantum mechanics. It finds uses in certain cosmological theories. Mathematically, imaginary time is real time which has undergone a Wick rotation so that its coordinates are multiplied by the imaginary unit i .
Mass flow rate is defined by the limit [3] [4] ˙ = =, i.e., the flow of mass through a surface per time .. The overdot on ˙ is Newton's notation for a time derivative.Since mass is a scalar quantity, the mass flow rate (the time derivative of mass) is also a scalar quantity.
The Hubble length or Hubble distance is a unit of distance in cosmology, defined as cH −1 — the speed of light multiplied by the Hubble time. It is equivalent to 4,420 million parsecs or 14.4 billion light years. (The numerical value of the Hubble length in light years is, by definition, equal to that of the Hubble time in years.)