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  2. Dirac delta function - Wikipedia

    en.wikipedia.org/wiki/Dirac_delta_function

    The graph of the Dirac delta is usually thought of as following the whole x-axis and the positive y-axis. [5]: 174 The Dirac delta is used to model a tall narrow spike function (an impulse), and other similar abstractions such as a point charge, point mass or electron point.

  3. Delta potential - Wikipedia

    en.wikipedia.org/wiki/Delta_potential

    The delta potential is the potential = (), where δ(x) is the Dirac delta function. It is called a delta potential well if λ is negative, and a delta potential barrier if λ is positive. The delta has been defined to occur at the origin for simplicity; a shift in the delta function's argument does not change any of the following results.

  4. Van 't Hoff equation - Wikipedia

    en.wikipedia.org/wiki/Van_'t_Hoff_equation

    When ⁠ B / C ⁠ < 1, C is the favored product, and the data on the Van 't Hoff plot will be in the negative region. Using this information, a Van 't Hoff analysis can help determine the most suitable temperature for a favored product.

  5. YΔ- and ΔY-transformation - Wikipedia

    en.wikipedia.org/wiki/YΔ-_and_ΔY-transformation

    For example, applying a YΔ-transformation to a 3-vertex of a planar graph, or a ΔY-transformation to a triangular face of a planar graph, results again in a planar graph. [1] This was used in the original proof of Steinitz's theorem , showing that every 3-connected planar graph is the edge graph of a polyhedron .

  6. Lambert W function - Wikipedia

    en.wikipedia.org/wiki/Lambert_W_function

    The product logarithm Lambert W function plotted in the complex plane from −2 − 2i to 2 + 2i The graph of y = W(x) for real x < 6 and y > −4. The upper branch (blue) with y ≥ −1 is the graph of the function W 0 (principal branch), the lower branch (magenta) with y ≤ −1 is the graph of the function W −1. The minimum value of x is ...

  7. Hessian matrix - Wikipedia

    en.wikipedia.org/wiki/Hessian_matrix

    The above rules stating that extrema are characterized (among critical points with a non-singular Hessian) by a positive-definite or negative-definite Hessian cannot apply here since a bordered Hessian can neither be negative-definite nor positive-definite, as = if is any vector whose sole non-zero entry is its first.

  8. Positive and negative parts - Wikipedia

    en.wikipedia.org/wiki/Positive_and_negative_parts

    The positive part and negative part of a function are used to define the Lebesgue integral for a real-valued function. Analogously to this decomposition of a function, one may decompose a signed measure into positive and negative parts — see the Hahn decomposition theorem .

  9. Hildebrand solubility parameter - Wikipedia

    en.wikipedia.org/wiki/Hildebrand_solubility...

    (However, PE only dissolves at temperatures well above 100 °C.) Poly(styrene) has a solubility parameter of 9.1 cal 1/2 cm −3/2, and thus ethyl acetate is likely to be a good solvent. Nylon 6,6 has a solubility parameter of 13.7 cal 1/2 cm −3/2, and ethanol is likely to be the best solvent of those tabulated. However, the latter is polar ...