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The name of Dirac cone comes from the Dirac equation that can describe relativistic particles in quantum mechanics, proposed by Paul Dirac. Isotropic Dirac cones in graphene were first predicted by P. R. Wallace in 1947 [6] and experimentally observed by the Nobel Prize laureates Andre Geim and Konstantin Novoselov in 2005. [7]
Two of the six Dirac points are independent, while the rest are equivalent by symmetry. In the vicinity of the K-points the energy depends linearly on the wave vector, similar to a relativistic particle. [4] [6] Since an elementary cell of the lattice has a basis of two atoms, the wave function has an effective 2-spinor structure.
The first technique developed was the far-field range, where the antenna under test (AUT) is placed in the far-field of a range antenna. Due to the size required to create a far-field range for large antennas, near-field techniques were developed, which allow the measurement of the field on a distance close to the antenna (typically 3 to 10 ...
The length of the antenna, D, is not important, and the approximation is the same for all shorter antennas (sometimes idealized as so-called point antennas). In all such antennas, the short length means that charges and currents in each sub-section of the antenna are the same at any given time, since the antenna is too short for the RF ...
When the two arms of a dipole are individually straight, but bent towards each other in a 'V' shape, at an angle noticeably less than 180°, the dipole is called a 'V' antenna, and when the dipole arms' ends are closer to the ground than their center branch-point, the antenna is called an inverted-'V' . The inverted-'V' is popular since it ...
In particle physics, the Dirac equation is a relativistic wave equation derived by British physicist Paul Dirac in 1928. In its free form , or including electromagnetic interactions, it describes all spin-1/2 massive particles , called "Dirac particles", such as electrons and quarks for which parity is a symmetry .
The pulse width (or pulse duration) of the transmitted signal is the time, typically in microseconds, each pulse lasts.If the pulse is not a perfect square wave, the time is typically measured between the 50% power levels of the rising and falling edges of the pulse.
The first antenna is the test antenna whose patterns are to be investigated; this antenna is free to point in any direction. The second antenna is a reference antenna, which points rigidly at the first antenna. Each antenna is alternately connected to a transmitter having a particular source impedance, and a receiver having the same input ...