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  2. Zero-inflated model - Wikipedia

    en.wikipedia.org/wiki/Zero-inflated_model

    One well-known zero-inflated model is Diane Lambert's zero-inflated Poisson model, which concerns a random event containing excess zero-count data in unit time. [8] For example, the number of insurance claims within a population for a certain type of risk would be zero-inflated by those people who have not taken out insurance against the risk ...

  3. Hurdle model - Wikipedia

    en.wikipedia.org/wiki/Hurdle_model

    A hurdle model is a class of statistical models where a random variable is modelled using two parts, the first of which is the probability of attaining the value 0, and the second part models the probability of the non-zero values. The use of hurdle models is often motivated by an excess of zeroes in the data that is not sufficiently accounted ...

  4. Archimedes' principle - Wikipedia

    en.wikipedia.org/wiki/Archimedes'_principle

    The net force on the object must be zero if it is to be a situation of fluid statics such that Archimedes principle is applicable, and is thus the sum of the buoyancy force and the object's weight F net = 0 = m g − ρ f V disp g {\displaystyle F_{\text{net}}=0=mg-\rho _{f}V_{\text{disp}}g\,}

  5. List of unsolved problems in chemistry - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    Protein folding problem: Is it possible to predict the secondary, tertiary and quaternary structure of a polypeptide sequence based solely on the sequence and environmental information? Inverse protein-folding problem: Is it possible to design a polypeptide sequence which will adopt a given structure under certain environmental conditions?

  6. Force field (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Force_field_(chemistry)

    Part of force field of ethane for the C-C stretching bond. In the context of chemistry, molecular physics, physical chemistry, and molecular modelling, a force field is a computational model that is used to describe the forces between atoms (or collections of atoms) within molecules or between molecules as well as in crystals.

  7. Combining rules - Wikipedia

    en.wikipedia.org/wiki/Combining_rules

    The Lennard-Jones Potential is a mathematically simple model for the interaction between a pair of atoms or molecules. [3] [4] One of the most common forms is = [() ()] where ε is the depth of the potential well, σ is the finite distance at which the inter-particle potential is zero, r is the distance between the particles.

  8. Interatomic potential - Wikipedia

    en.wikipedia.org/wiki/Interatomic_potential

    The term force field characterizes the collection of parameters for a given interatomic potential (energy function) and is often used within the computational chemistry community. [50] The force field parameters make the difference between good and poor models. Force fields are used for the simulation of metals, ceramics, molecules, chemistry ...

  9. DLVO theory - Wikipedia

    en.wikipedia.org/wiki/DLVO_theory

    DLVO theory is the combined effect of van der Waals and double layer force. For the derivation, different conditions must be taken into account and different equations can be obtained. [13] But some useful assumptions can effectively simplify the process, which are suitable for ordinary conditions.