Abstract: The present disclosure relates to an organic electroluminescent compound, a plurality of host materials, and an organic electroluminescent device comprising the same. By comprising the compound according to the present disclosure or by comprising a specific combination of compounds according to the present disclosure as a plurality of host materials, it is possible to produce an organic electroluminescent device having improved driving voltage, luminous efficiency, and/or lifetime properties compared to the conventional organic electroluminescent devices.

Abstract: Disclosed is an X-ray tube for improving electron focusing, which allows thermoelectrons emitted from a filament to efficiently reach a target of an X-ray irradiation window. To achieve this, the X-ray tube includes: a thermionic emitter configured to emit thermoelectrons by application of a negative high voltage; a focusing tube configured to focus the thermoelectrons emitted from the thermionic emitter; an X-ray irradiation window configured to irradiate X-rays outside by the thermoelectrons bombarded on a target distributed on the X-ray irradiation window, to generate the X-rays after the thermoelectrons pass through the focusing tube; a tube part including both the thermionic emitter and the focusing tube; and a housing surrounding the tube part, wherein the focusing tube and the housing are configured to have a same potential such that movement directions of the thermoelectrons are directed to the X-ray irradiation window.

Abstract: Disclosed is an X-ray tube for improving electron focusing, which allows thermoelectrons emitted from a filament to efficiently reach a target of an X-ray irradiation window. To achieve this, the X-ray tube includes: a thermionic emitter configured to emit thermoelectrons by application of a negative high voltage; a focusing tube configured to focus the thermoelectrons emitted from the thermionic emitter; an X-ray irradiation window configured to irradiate X-rays outside by the thermoelectrons bombarded on a target distributed on the X-ray irradiation window, to generate the X-rays after the thermoelectrons pass through the focusing tube; a tube part including both the thermionic emitter and the focusing tube; and a housing surrounding the tube part, wherein the focusing tube and the housing are configured to have a same potential such that movement directions of the thermoelectrons are directed to the X-ray irradiation window.