Differential Mode Delay

Robustness and a good resistance to temperature treatments are the advantages of solid state membranes. They allow new devices to be conceived, for instance, in FIA tubular cells or for specific applications, in particirlar if the materials are very good ionic conductors. Measurements in FIA cells can be made in differential mode by a change of solution during a short delay. In this matmer, the voltage drift is a minor disadvantage. 

Further accuracy improvement was experienced when two or more receivers were used simultaneously at two or more stationary points, and relative positions in terms of interstation vectors Ar were produced. The reason for the increased accuracy was the attenuation of the effect of conrmon errors/biases (atmospheric delays, orbital errors, etc.) through differencing. This relative or differential mode of using the system became very popular and remains the staple mode for geodetic positioning even with the more modem GPS used today. 

The outline of this paper is as follows. First, a theoretical model of unsteady motions in a combustion chamber with feedback control is constructed. The formulation is based on a generalized wave equation which accommodates all influences of acoustic wave motions and combustion responses. Control actions are achieved by injecting secondary fuel into the chamber, with its instantaneous mass flow rate determined by a robust controller. Physically, the reaction of the injected fuel with the primary combustion flow produces a modulated distribution of external forcing to the oscillatory flowfield, and it can be modeled conveniently by an assembly of point actuators. After a procedure equivalent to the Galerkin method, the governing wave equation reduces to a system of ordinary differential equations with time-delayed inputs for the amplitude of each acoustic mode, serving as the basis for the controller design. 

To reduce the kinetic energy spread among ions with the same m/z ratio leaving the source, a time lag or delay between ion formation and extraction can be introduced. The ions are first allowed to expand into a field-free region in the source and after a certain delay (hundreds of nanoseconds to several microseconds) a voltage pulse is applied to extract the ions outside the source. This mode of operation is referred to as delayed pulsed extraction to differentiate it from continuous extraction used in conventional instruments. Delayed pulsed extraction, also known as pulsed ion extraction, pulsed extraction or dynamic extraction, is a revival of time-lag focusing, which was initially developed by Wiley and McLaren in the 1950s, shortly after the appearance of the first commercial TOF instrument. 

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