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  2. Cepstrum - Wikipedia

    en.wikipedia.org/wiki/Cepstrum

    The method is a tool for investigating periodic structures in frequency spectra. The power cepstrum has applications in the analysis of human speech. The term cepstrum was derived by reversing the first four letters of spectrum. Operations on cepstra are labelled quefrency analysis (or quefrency alanysis [1]), liftering, or cepstral analysis.

  3. List of unsolved problems in physics - Wikipedia

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

    Some of the major unsolved problems in physics are theoretical, meaning that existing theories seem incapable of explaining a certain observed phenomenon or experimental result. The others are experimental, meaning that there is a difficulty in creating an experiment to test a proposed theory or investigate a phenomenon in greater detail.

  4. List of thread standards - Wikipedia

    en.wikipedia.org/wiki/List_of_thread_standards

    A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is an inclined plane wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread.

  5. Spectrum (topology) - Wikipedia

    en.wikipedia.org/wiki/Spectrum_(topology)

    The stable homotopy category, or homotopy category of (CW) spectra is defined to be the category whose objects are spectra and whose morphisms are homotopy classes of maps between spectra. Many other definitions of spectrum, some appearing very different, lead to equivalent stable homotopy categories.

  6. Pentalobular screw thread - Wikipedia

    en.wikipedia.org/wiki/Pentalobular_screw_thread

    A pentalobular screw thread is a form of self-forming thread used for screws. Self-forming screws are used in ductile materials, such as aluminium and plastics. Self-tapping screws are widely used for driving into sheet metal or plastics and forming their own thread. They may be either self-drilling, forming their own hole through unbroken ...

  7. Tetrachromacy - Wikipedia

    en.wikipedia.org/wiki/Tetrachromacy

    The four pigments in a bird's cone cells (in this example, estrildid finches) extend the range of color vision into the ultraviolet. [1]Tetrachromacy (from Greek tetra, meaning "four" and chroma, meaning "color") is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cell in the eye.

  8. Spectrum - Wikipedia

    en.wikipedia.org/wiki/Spectrum

    A spectrum (pl.: spectra or spectrums) [1] is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word spectrum was first used scientifically in optics to describe the rainbow of colors in visible light after passing through a prism .

  9. Mössbauer spectroscopy - Wikipedia

    en.wikipedia.org/wiki/Mössbauer_spectroscopy

    Just as a gun recoils when a bullet is fired, conservation of momentum requires a nucleus (such as in a gas) to recoil during the emission or absorption of a gamma ray. If a nucleus at rest emits a gamma ray, the energy of the gamma ray is slightly less than the natural energy of the transition, but in order for a nucleus at rest to absorb a gamma ray, the gamma ray's energy must be slightly ...