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1. An act that requires use of resources or time. In Program Evaluation and Review Technique (PERT), an activity is represented by an arrow on a PERT chart.

2. In investing, the amount of a security's relative trading volume; that is, the amount of money flowing into and out of a security in trading. A high amount of activity means that many shares of the security are being bought and sold at a high rate, while a low level of activity indicates the opposite.
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The amount of relative trading volume in a security.
Wall Street Words: An A to Z Guide to Investment Terms for Today's Investor by David L. Scott. Copyright © 2003 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved. All rights reserved.
References in periodicals archive ?
Activity coefficient of a species in a solution represents the relation between the real fugacity and the fugacity corresponding to an ideal solution (calculated via Lewis-Randall rule).
These solvent heats of vaporization values, derived from the experimentally determined activity coefficients, can be compared with the ones estimated employing the Watson model [18] as a kind of consistency test, in order to check the goodness of the experimental data.
Hence, the VLE model itself is valid at low acid gas partial pressures even though the parameters of the activity coefficient model were not fitted in this range (Kundu, 2004).
The extrapolation method of Harned and Ehlers, which expressed the activity coefficient in eq (1) by the Debye-Huckel limiting law, was used to obtain all of the potentials except those given in the last column.
In the electroneutral mixture method of the COSMO-RS, in order to estimate the activity coefficient ([gamma]), a mixture of ILs and solute was treated as ternary system (1: 1 IL, cation + anion + solute) that can be converted into a binary system.
where [[gamma].sub.i] is the activity coefficient of component i in the ternary mixture of the composition [x.sub.i], [x.sub.j], [x.sub.k], and
[a.sup.C.sub.i] = [[omega].sub.i][[OMEGA].sup.C.sub.i] it follows that, for the elastic contribution, the activity is equal to the activity coefficient [a.sup.el.sub.i] = [[OMEGA].sup.el.sub.i].
Dependences of the activity coefficient upon temperature and composition of the investigated system alloy can be calculated within the framework of the Redlich--Kister model [7].
The activity coefficient of an adsorbed ion represents the degree of freedom that it has to leave the adsorbed state towards the unitary standard state of maximum freedom, and therefore reflects the heterogeneity of the exchange process (Goulding 1983).
[16], because of the change of ion environment, the change of activity coefficient and liquid junction potential error could modify the ion data as Na[HCO.sub.3] is substituted for NaCl.
The weight fraction activity coefficient (1) of the solute at infinite dilution can be calculated from following relation [28].