A method for making a semiconductor epitaxial structure is provided. Control of a pump rotation speed by a pressure sensor has low responsiveness in a low pressure region, and a correlation between a pressure and a flow rate is incomplete in a high flow rate region. The housing introduces the gas stream. The 2nd server processes the concurrent additional request via the 2nd RAID such that processing of multiple requests for the same video program is distributed throughout the video on demand system. The outer sheath is designed to retain the medical device for lengthy periods of time while the inner sheath is designed to retain the sheath for shorter periods of time.