activity

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activity

1. the number of disintegrations of a radioactive substance in a given unit of time, usually expressed in curies or disintegrations per second
2. 
a. the capacity of a substance to undergo chemical change
b. the effective concentration of a substance in a chemical system. The absolute activity of a substance B, λB, is defined as exp (μBRT) where μB is the chemical potential

activity

[‚ak′tiv·əd·ē]
(computer science)
The use or modification of information contained in a file.
(nuclear physics)
The intensity of a radioactive source. Also known as radioactivity.
(physical chemistry)
A thermodynamic function that correlates changes in the chemical potential with changes in experimentally measurable quantities, such as concentrations or partial pressures, through relations formally equivalent to those for ideal systems.
(systems engineering)
The representation in a PERT or critical-path-method network of a task that takes up both time and resources and whose performance is necessary for the system to move from one event to the next.

activity

In CPM terminology, a task or item of work that must be performed in order to complete a project.
References in periodicals archive ?
Table-4 shows the relative deviation (RDX) for each experimental fusion enthalpy tested using the same data of activity coefficient model.
where A is alkalinity, a is activity, 0.94 is an empirical coefficient accounting for the contribution of carbonate alkalinity to the total alkalinity of soil solution [Alk.sub.[SIGMA]]; y' is the activity coefficient of the singly charged particle (free ion or its associate); and y" is the activity coefficient of the doubly charged particle (Minkina et al., 2012a).
Then, it discusses the proposed methodology for calculating fugacity and activity coefficients in the selected binary samples, showing the main equations required for its determination.
Caption: FIGURE 8: Activity coefficients (a) [[gamma].sub.DPPC] and (b) [[gamma].sub.CUR] of mixed DPPC-CUR monolayers versus [X.sub.CUR] at discrete surface pressures.
Computerized design of multicomponent distillation columns using the UNIFAC group contribution method for calculation of activity coefficients. Industrial & Engineering Chemistry Process Design and Development 16 (4), 450-462.
The modified Clegg-Pitzer equations have been used to derive the activity coefficients of different species present in the equilibrated liquid phase (Li and Mather, 1994; Kundu et al., 2003; Kundu and Bandyopadhyay, 2005).
The activity coefficients and other thermodynamic properties of hydrochloric acid are dependent not upon the value of E[degrees] but on the difference E-E[degrees].
ACTIVITY COEFFICIENTS FOR THE SYSTEM HCl + [YCl.sub.3] + [H.sub.2]O AT 5[degrees]C, 25[degrees]C, 55[degrees]C.
Calculations concerning solubilities based on solubility products, effects of common ions and pH, and the calculation of activity coefficients are presented in chapters 3 and 6.
In this study, IGC was successfully applied to determine certain thermodynamic and pyhsical properties of poly(ABM), poly(ABM0.41-co-AN) and poly(ABM0.71-co-AN), such as the glass transition temperature, Tg; the sorption enthalpy, IH 1S, sorption free energy, IG 1S; sorption entropy, IS 1S; the weight fraction activity coefficients, a| 1a; partial molar free energy of mixing, IG 1a; partial molar heat of mixing, IH 1a; and the Flory-Huggins interaction parameters, I 12a, at infinite dilution.
Finally, limiting activity coefficients of benzene and alcohols in swelled LDPE calculated from constants in Table 2 were compared with values estimated from the modified UNIFAC [43, 53] assuming that the solvent is a hypothetical liquid hydrocarbon that has the same density as LDPE.