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  2. Summation by parts - Wikipedia

    en.wikipedia.org/wiki/Summation_by_parts

    The formula for an integration by parts is () ′ = [() ()] ′ (). Beside the boundary conditions , we notice that the first integral contains two multiplied functions, one which is integrated in the final integral ( g ′ {\displaystyle g'} becomes g {\displaystyle g} ) and one which is differentiated ( f {\displaystyle f} becomes f ...

  3. Joback method - Wikipedia

    en.wikipedia.org/wiki/Joback_method

    Principle of a group-contribution method. The Joback method is a group-contribution method.These kinds of methods use basic structural information of a chemical molecule, like a list of simple functional groups, add parameters to these functional groups, and calculate thermophysical and transport properties as a function of the sum of group parameters.

  4. Direct sum of groups - Wikipedia

    en.wikipedia.org/wiki/Direct_sum_of_groups

    The group operation in the external direct sum is pointwise multiplication, as in the usual direct product. This subset does indeed form a group, and for a finite set of groups {H i} the external direct sum is equal to the direct product. If G = ΣH i, then G is isomorphic to Σ E {H i}. Thus, in a sense, the direct sum is an "internal ...

  5. Summation - Wikipedia

    en.wikipedia.org/wiki/Summation

    In mathematics, summation is the addition of a sequence of numbers, called addends or summands; the result is their sum or total.Beside numbers, other types of values can be summed as well: functions, vectors, matrices, polynomials and, in general, elements of any type of mathematical objects on which an operation denoted "+" is defined.

  6. Direct product of groups - Wikipedia

    en.wikipedia.org/wiki/Direct_product_of_groups

    For example, if G is any group, then there exists an automorphism σ of G × G that switches the two factors, i.e. σ(g 1, g 2) = (g 2, g 1). For another example, the automorphism group of Z × Z is GL(2, Z), the group of all 2 × 2 matrices with integer entries and determinant, ±1. This automorphism group is infinite, but only finitely many ...

  7. Direct sum - Wikipedia

    en.wikipedia.org/wiki/Direct_sum

    The direct sum is also commutative up to isomorphism, i.e. for any algebraic structures and of the same kind. The direct sum of finitely many abelian groups, vector spaces, or modules is canonically isomorphic to the corresponding direct product. This is false, however, for some algebraic objects, like nonabelian groups.

  8. Ramanujan's sum - Wikipedia

    en.wikipedia.org/wiki/Ramanujan's_sum

    In number theory, Ramanujan's sum, usually denoted c q (n), is a function of two positive integer variables q and n defined by the formula = (,) =,where (a, q) = 1 means that a only takes on values coprime to q.

  9. Molien's formula - Wikipedia

    en.wikipedia.org/wiki/Molien's_formula

    Consider the symmetric group acting on R 3 by permuting the coordinates. We add up the sum by group elements, as follows. Starting with the identity, we have = ().There is a three-element conjugacy class of , consisting of swaps of two coordinates.