Abstract: A membrane includes a blend of two or more polymers such that under operating conditions of a separation using the membrane the operating temperature is greater than at least one glass transition temperature of the blend. A membrane includes a blend of polymers exhibiting calculated &dgr;a of the membrane material value is greater than 7.5. A membrane includes a blend of polymers exhibiting a calculated solubility selectivity for a separation of interest greater than 1. A membrane includes a blend of polymers having polar functional groups and non-polar functional groups wherein the composition of the blend is selected so that the interaction of the polar functional groups and the non-polar functional groups with a permeating species leads to preferential solubility selectivity. A polymer blend for performing a separation includes at least one rubbery polymer having a glass transition temperature no greater than 20° C. and at least one glassy polymer having a glass transition temperature above 20° C.

Abstract: An ultrasonic flow velocity measuring apparatus measures a transit time under the condition a synchronization of an ultrasonic signal having a modulated frequency by PN (pseudo noise) code of a diffusion band at a transmitting side is locked at a receiving side, and prevents an excessive measurement error exceeding allowable error range. If the installation positions of the ultrasonic transducers of upper and lower stream sides are moved, an ultrasonic transit time can be precisely measured by using a different signal series PN code without changing an electronic component and a program. In addition, the ultrasonic flow velocity measuring apparatus installs a plurality of ultrasonic transducers according to various distances from the bottom of a fluid passage, and accurately measures average flow velocity which is variable in response to the height in a curved fluid passage.