Time variations in the particle number concentration and particle size distribution in a circular pipe flow are numerically calculated from the equation of population balance undergoing coagulation due to a laminar shear flow. Next, the effects of various parameters related to silting phenomena are clarified using “silting time”, which is theoretically obtained as the time required for the occurrence of silting at the inner or inlet part of a capillary passage.
Results are as follows :
1) The experimental results are qualitatively explained by “silting time” derived from the equation of population balance.
2) Effects of the ratio of average particle size to the inner diameter of the capillary passage regarding silting time qualitatively agree with that of those parameters concerning silting frequency.

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The on-off controlled pneumatic servo system using the high speed solenoid valves instead of a servo proportional valve is very compact in form and has very high operating accuracy. In this system, the opening and closing periods of valves must be modulated according to system state values. Design for optimal control is quite difficult, since the system parameters vary with sampling time.
System parameters are not required for the Model Reference Adapting Control (MRAC) law. MRAC is induced to lessen the number of calculation of system parameters. MRAC design is shown and the effects of varying sampling time are discussed. A comparison is made of the performance of indirect law and direct law MRACs.

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In oil hydraulic systems, components such as pumps, motors and valves often cause flow and pressure oscillation, with consequent vibration and noise, and possibly a breakdown of the system. To avoid such situations, one of the present authors had proposed a π-filter consisting of branch pipes and as a result, pulsation had been completely eliminated. The π-filter could not sufficiently reduce pulsation right at the pump out-port, though. To develop an oil hydraulic filter without this drawback, examination was made of the use of a Helmholtz resonator, a conventional detector in acoustics. The impedance of an 'oil hydraulic' Helmholtz resonator was found to be -60 dB lower than the characteristic impedance at the neck at an anti-resonant frequency. It should thus serve adequately as a filter. To estimate anti-resonant frequency and impedance of a resonator, the wave motion of oil in the resonator volume and unsteady viscous loss in the neck tube must be taken into consideration. The plane wave approximation was found appropriate for a cylindrical resonator under the condition of a large length-to-diameter ratio. The resonator thoroughly absorbed flow rate pulsation from the gear pump, thus demonstrating its usefulness as a filter to adequately eliminate pulsation.

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