cross section

(noun)

A section formed by a plane cutting through an object, usually at right angles to an axis.

Related Terms

  • dimension

Examples of cross section in the following topics:

  • Absorption

    • Phenomenologically you can imagine that there are many independent absorbers in the beam, each with a cross section $\sigma_\nu$ and a number density $n$.
    • You can think of this as the cross section per unit mass of the absorbers.
  • A Physical Aside: Einstein coefficients

    • Fermi's Golden Rule relates the cross-section for a process to a quantum mechanical matrix element and the phase space available for the products.
    • Because quantum mechanics for the most part is time reversible, the cross-section for the forward and reverse reactions are related.
  • Inputs

    • The main inputs of forecasting include time series, cross-sectional and longitudinal data, or using judgmental methods.
    • Both might refer to formal statistical methods employing time series, cross-sectional or longitudinal data, or less formal judgmental methods.
    • Analysis of cross-sectional data usually consists of comparing the differences among the subjects.
    • This cross-sectional sample provides us with a snapshot of that population, at that one point in time.
    • Cross-sectional data differs from time series data also known as longitudinal data, which follows one subject's changes over the course of time.
  • Driven Harmonic Oscillator

    • Let's imagine that our harmonic oscillator is driven by incoming electromagnetic wave.Using the assumptions from the section on scattering and the radiation reaction we have
    • Let's divide by the Poynting vector $\left \langle S \right \rangle = (c/8\pi) E_0^2$ to get the scattering cross-section
    • Near the resonance the cross-section has the same profile at the spontaneous emission.
  • Flow Rate and the Equation of Continuity

    • where Q is the flow rate, v is the velocity of the fluid, and a is the area of the cross section of the space the fluid is moving through.
    • Speed increases when cross-sectional area decreases, and speed decreases when cross-sectional area increases.
  • Volume

    • The volume of a cylinder: the cross-sectional area times the height of the cylinder.
    • Measuring cups, as seen in , work by taking a known cross sectional area of a cup and multiplying that by a variable height.
    • Since liquid will always cover the cross section (if there is enough liquid), adding more liquid will increase the height inside the container.
  • CAM and C4 Photosynthesis

    • Cross section of a CAM (crassulacean acid metabolism) plant, specifically of an agave leaf.
    • Cross section of a C4 plant, specifically of a maize leaf.
  • Methods for Researching Human Development

    • These include longitudinal, cross-sectional, sequential, and microgenetic designs.
    • In a cross-sectional study, a researcher observes differences between individuals of different ages at the same time.
    • Cross-sequential designs combine both longitudinal and cross-sectional design methodologies.
    • In contrast to longitudinal and cross-sectional designs, which provide broad outlines of the process of change, microgenetic designs provide an in-depth analysis of children's behavior while it is changing.
  • Control of Muscle Tension

    • Muscle tension is influenced by the number of cross-bridges that can be formed.
    • In individual muscle fibers, the amount of tension produced depends primarily on the amount of cross-bridges formed, which is influenced by the cross-sectional area of the muscle fiber and the frequency of neural stimulation.
    • The number of cross-bridges formed between actin and myosin determine the amount of tension that a muscle fiber can produce.
    • Cross-bridges can only form where thick and thin filaments overlap, allowing myosin to bind to actin.
    • If more cross-bridges are formed, more myosin will pull on actin and more tension will be produced.
  • What Are Conic Sections?

    • A focus is a point about which the conic section is constructed.
    • These properties that the conic sections share are often presented as the following definition, which will be developed further in the following section.
    • Each type of conic section is described in greater detail below.
    • The nappes and the four conic sections.
    • Describe the parts of a conic section and how conic sections can be thought of as cross-sections of a double-cone
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