A filter element includes a flat dielectric substrate, a ground electrode on a back main surface of the dielectric substrate, resonant lines each having a shorting end in the vicinity of a border between a side of the dielectric substrate and the ground electrode and extending from the side to a front main surface of the dielectric substrate. The transmission comprises a first shaft that is connectable to the internal combustion engine, a second rotation shaft that is connectable to the electric motor, and a third rotation shaft that is connected to drive wheels. The n-type silicon oxide film includes a plurality of quantum dots composed of n-type Si while the p-type silicon nitride film includes a plurality of quantum dots composed of p-type Si. The alkaline solution may be present in a formate-based drilling fluid displaced into the wellbore ahead of the cement slurry.