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  2. Density matrix - Wikipedia

    en.wikipedia.org/wiki/Density_matrix

    In quantum mechanics, a density matrix (or density operator) is a matrix that describes an ensemble [1] of physical systems as quantum states (even if the ensemble contains only one system). It allows for the calculation of the probabilities of the outcomes of any measurements performed upon the systems of the ensemble using the Born rule .

  3. High-density polyethylene - Wikipedia

    en.wikipedia.org/wiki/High-density_polyethylene

    HDPE is known for its high strength-to-density ratio. [4] The density of HDPE ranges from 930 to 970 kg/m 3. [5] Although the density of HDPE is only marginally higher than that of low-density polyethylene, HDPE has little branching, giving it stronger intermolecular forces and tensile strength (38 MPa versus 21 MPa) than LDPE. [6]

  4. Joint probability distribution - Wikipedia

    en.wikipedia.org/wiki/Joint_probability_distribution

    Toggle Joint density function or mass function subsection. 4.1 Discrete case. 4.2 Continuous case. 4.3 Mixed case. 5 Additional properties. ... For example, for A the ...

  5. Physiological density - Wikipedia

    en.wikipedia.org/wiki/Physiological_density

    A higher physiological density suggests that the available agricultural land is being used by more and may reach its output limit sooner than a country that has a lower physiological density. Egypt is a notable example, with physiological density reaching that of Bangladesh, despite much desert.

  6. Vapour density - Wikipedia

    en.wikipedia.org/wiki/Vapour_density

    vapour density = molar mass of gas / molar mass of H 2 vapour density = molar mass of gas / 2.01568 vapour density = 1 ⁄ 2 × molar mass (and thus: molar mass = ~2 × vapour density) For example, vapour density of mixture of NO 2 and N 2 O 4 is 38.3. Vapour density is a dimensionless quantity. Vapour density = density of gas / density of ...

  7. Bulk density - Wikipedia

    en.wikipedia.org/wiki/Bulk_density

    The bulk density of soil depends greatly on the mineral make up of soil and the degree of compaction. [3] The density of quartz is around 2.65 g/cm 3 but the (dry) bulk density of a mineral soil is normally about half that density, between 1.0 and 1.6 g/cm 3.

  8. Linear density - Wikipedia

    en.wikipedia.org/wiki/Linear_density

    Consider a long, thin rod of mass and length .To calculate the average linear mass density, ¯, of this one dimensional object, we can simply divide the total mass, , by the total length, : ¯ = If we describe the rod as having a varying mass (one that varies as a function of position along the length of the rod, ), we can write: = Each infinitesimal unit of mass, , is equal to the product of ...

  9. Current density - Wikipedia

    en.wikipedia.org/wiki/Current_density

    In electromagnetism, current density is the amount of charge per unit time that flows through a unit area of a chosen cross section. [1] The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional area at a given point in space, its direction being that of the motion of the positive charges at this point.