cross section

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