Abstract: A wafer with a buried V-groove cavity, and a method for fabricating V-grooves. In some embodiments, the method includes bonding a first layer, to a top surface of a substrate, to form a composite wafer, the first layer being composed of a first semiconductor material, the substrate being composed of a second semiconductor material, the top surface of the substrate having a cavity, the cavity including a V-groove.

Abstract: The electric machine comprises a cylindrical rotor with axial first air channels and a stator with axial second air channels. The outer surface of the stator is provided with cooling fins. There is a first air chamber at a first end of the rotor, a second air chamber and an adjacent third air chamber at a second end of the rotor. A first fan circulates internal air from the first axial air channels to the second air channels in a closed air circulation within the electric machine. A second fan blows external cooling air from the outside of the electric machine through the third air chamber and from the outlet opening of the third air chamber along the outer surface of the stator. The number of second air channels in the stator is three.

Abstract: The electric machine comprises a cylindrical rotor with axial first air channels and a stator with axial second air channels. The outer surface of the stator is provided with cooling fins. There is a first air chamber at a first end of the rotor, a second air chamber and an adjacent third air chamber at a second end of the rotor. A first fan circulates internal air from the first axial air channels to the second air channels in a closed air circulation within the electric machine. A second fan blows external cooling air from the outside of the electric machine through the third air chamber and from the outlet opening of the third air chamber along the outer surface of the stator. The number of second air channels in the stator is three.

Abstract: In the arrangement in a heat exchanger in accordance with the invention, the heat exchanger comprises a shell and tubes. The tubes are placed inside the shell. The first medium entering the heat exchanger can be conducted into the tubes and the second medium between the inner shell surface and outer tube surface, and the first medium from the heat exchanger can be conducted out from the tubes and the second medium out from between the inner shell surface and outer tube surface. The heat exchanger comprises at least two tube rows placed in succession in the direction of the second medium's flow. The first tube row comprises at least two tubes, the first distance being between the two parallel tubes, the second distance being between the first parallel tube in the first row and a tube in the second row, and the third distance is between the second parallel tube in the first row and the tube in the second row.