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The strong CP problem is a question in particle physics, which brings up the following quandary: why does quantum chromodynamics (QCD) seem to preserve CP-symmetry? In particle physics, CP stands for the combination of C-symmetry (charge conjugation symmetry) and P-symmetry (parity symmetry).
The following is a list of notable unsolved problems grouped into broad areas of physics. [1]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.
Quantitative tests of non-perturbative QCD are fewer, because the predictions are harder to make. The best is probably the running of the QCD coupling as probed through lattice computations of heavy-quarkonium spectra. There is a recent claim about the mass of the heavy meson B c. Other non-perturbative tests are currently at the level of 5% at ...
Two-dimensional projection of a hyperspectral cube. Hyperspectral imaging collects and processes information from across the electromagnetic spectrum. [1] The goal of hyperspectral imaging is to obtain the spectrum for each pixel in the image of a scene, with the purpose of finding objects, identifying materials, or detecting processes.
In mechanical engineering, the thread angle of a screw is the included angle between the thread flanks, measured in a plane containing the thread axis. [1] This is a defining factor for the shape of a screw thread .
A blazed diffraction grating reflecting only the green portion of the spectrum from a room's fluorescent lighting. For a diffraction grating, the relationship between the grating spacing (i.e., the distance between adjacent grating grooves or slits), the angle of the wave (light) incidence to the grating, and the diffracted wave from the grating is known as the grating equation.
Both tools can be used to clean up a thread, which is called chasing. However, using an ordinary tap or die to clean threads generally removes some material, which results in looser, weaker threads. Because of this, machinists generally clean threads with special taps and dies—called chasers—made for that purpose. Chasers are made of softer ...
The trapezoidal metric thread form is similar to the Acme thread form, except the thread angle is 30°. [4] [5] [6] It is codified by DIN 103. [7] While metric screw threads are more prevalent worldwide than imperial threads for triangular thread forms, the imperially sized Acme threads predominate in the trapezoidal thread form.