Abstract: A stethoscope includes a tube and a sound conducting assembly. The tube is formed by a plastic injection molding process or a thermal forming process. The sound conducting assembly is disposed in the tube. The tube is completely formed by another plastic injection molding process or another thermal forming process to enclose the sound conducting assembly. The stethoscope is directly obtained in the injection molding machine, and the step of inserting the sound conducting assembly through the tube is not needed.

Abstract: In a hybrid transportation apparatus, a gas supply provides high-pressure hydrogen, which drives a turbine to generate first mechanical power and becomes medium-pressure hydrogen, which drives an air engine to generate second mechanical power and becomes low-pressure hydrogen. A fuel cell generates first electric power according to the low-pressure hydrogen. A heat recycling module recycles heat, which is generated by the fuel cell, to warm up the high-pressure hydrogen or the medium-pressure hydrogen. A generator receives the first mechanical power and generates second electric power. A motor generates third mechanical power according to the first and second electric power. A power output device causes movement of the transportation apparatus according to the second and third mechanical power. Thus, potential energy and chemical energy of the high-pressure hydrogen can be effectively utilized to generate the mechanical power and the electric power to move the transportation apparatus.

Abstract: An air engine includes a cylinder, a piston, a gas supply and an intake-exhaust mechanism. The gas supply supplies a compressed gas to move the piston reciprocating in the cylinder. The intake-exhaust mechanism connected to the cylinder and the gas supply includes a body and an intake-exhaust assembly. The body has a chamber, and an intake channel, an exhaust channel, an inlet port and an outlet port, which communicate with the chamber. The intake-exhaust assembly, rotatable within the chamber, controls the inlet port to be connected to the intake channel, and further controls the outlet port to be connected to the exhaust channel, so that the compressed gas enters the cylinder via the inlet port and the intake channel to drive the piston. After driving the piston, the compressed gas becomes an exhaust gas, which is exhausted from the cylinder via the exhaust channel and the outlet port.