Abstract: A log feeding apparatus for feeding a log to first and second cutting spindles is provided, in which a log is fed to a second receiving position when centering spindles have reached a second delivery position that is away from the second receiving position downstream in the direction of log transport by a distance equal to or greater than an assumed maximum diameter of the log. That is, a new log is transported to the second receiving position by placing sections when the log held between the centering spindles reaches a position that will avoid contact with the new log. As a result, the time can be reduced for transporting the log to the cutting spindles.

Abstract: When the absolute value (|Tt?Tc|) of the difference between the turning time Tt of a log PW and the transport time Tc of the log PW is longer than a reference measurement time Ts, the turning-axis center line measurement time Tm is set to the absolute value (|Tt?Tc|) (Step S120), the rotation speed W of centering spindles 24a and 24b is set to a speed (Ws×Ts/Tm) lower than a reference rotation speed Ws, and also the measurement rotation angle ? is set to an angle (?s×Ts/Tm) smaller than a reference measurement rotation angle as (Step S122). When the absolute value (|Tt?Tc|) is equal to or less than the reference measurement time Ts, the turning-axis center line measurement time Tm is set to the reference measurement time Ts (Step S116), the rotation speed W of the centering spindles 24a and 24b is set to the reference rotation speed Ws, and also the measurement rotation angle ? is set to the reference measurement rotation angle ?s (Step S118).

Abstract: A semiconductor substrate includes a single crystal Ga2O3-based substrate and a polycrystalline substrate that are bonded to each other. A thickness of the single crystal Ga2O3-based substrate is smaller than a thickness of the polycrystalline substrate, and a fracture toughness value of the polycrystalline substrate is higher than a fracture toughness value of the single crystal Ga2O3-based substrate.

Abstract: A log feeding apparatus for feeding a log to first and second cutting spindles is provided, in which a log is fed to a second receiving position when centering spindles have reached second delivery position that is away from the second receiving position downward in the direction of log transport by a distance equal to or greater than an assumed maximum diameter of the log. That is, a new log is transported to the second receiving position when the log transported by placing sections reaches a position not to contact the log held between the centering spindles. As a result, the time can be reduced for transporting the log to the cutting spindles.

Abstract: A semiconductor substrate includes a single crystal Ga2O3-based substrate and a polycrystalline substrate that are bonded to each other. A thickness of the single crystal Ga2O3-based substrate is smaller than a thickness of the polycrystalline substrate, and a fracture toughness value of the polycrystalline substrate is higher than a fracture toughness value of the single crystal Ga2O3-based substrate.