In one aspect, an apparatus for use in a wellbore is disclosed, including: an inlet; an outlet; and a variable flow restriction configured to provide a predetermined constant pressure drop between the inlet and the outlet in response to a range of inlet flow rates. A number of radial elements project from the mixing shaft, and carry paddles at their distal ends, adjacent the sidewall of the vessel. The base has a vertical plugging chamber for a fitting portion and two conducting teeth of a lamp to plug in. Then, the concentration of each component is fed into a second phase radial basis function neural network, which correlates the concentration of each component with the intensities of saltiness, sourness, sweetness, umami and bitterness sensed by humans, to calculate the intensities of saltiness, sourness, sweetness, umami and bitterness sensed by humans. Other embodiments may be described and claimed. A drive belt extends around and engages both the drive pulley and the generator pulley.