Velocity pulsing

In reverse-pulse applications, most plants rely on plant-air systems as the source for the high-velocity pulses required for cleaning. In many cases, however, the plant-air system is not sufficient for this purpose. Although the pulses required are short (i.e., 100 milliseconds or less), the number and frequency can deplete the supply. Therefore, care must be taken to ensure that both sufficient volume and pressure are available to achieve proper cleaning. 

Figure 11.18 Silicon nitride-based coatings on steel produced by (a) detonation spraying (Berger et al., 1998) and (b) ultrahigh-velocity pulsed plasma spraying (Usuba and Heimann,...

Usuba, S. and Heimann, R.B. (2006) Dense Si3N4 coatings with high friction coefficient deposited by high-velocity pulsed plasma spraying. /. Therm. Spray Technol, 15 (3), 356-363. 

Since the indirect evaluation of the behavior factor intrinsically included the uncertainty of both the elastic spectral amplification as well as the inelastic reduction, the scatter between target and actual ductilities or strength demands was high. Furthermore, use of a constant over a period range or over the entire period range, as originally adopted in ATC (1978), was shown to be inadequate to Umit the inelastic demands of SDOF systems, particularly for near-held earthquake events with severe velocity pulses (Mahin and Bertero 1981). 

In Fig. 1 examples of accelerometric and velocimetric time series recorded close to the source at sites located on rock and stiff soil (STS and AQA stations) and intermediate distances on soft sites (MDN and CESV) are plotted. Each time series is characterized by peculiar features, such as (i) presence of surface waves (MDN) (ii) impulsive behavior (STS) (iii) low-frequency velocity pulse (AQA) and (iv) absence of low-frequency waves (CESV). 

Not all ground motion time histories recorded at stations in the vicinity of a fault exhibit intense velocity pulses. The existence of pulse-like ground motions in near-fault records primarily depends on the relative position of the station that recorded the motion with respect to the direction of propagation of rupture on the causative fault plane and on the magnitude and direction of slip on that segment of the fault that is located in the vicinity of the station. Whenever these ground motion pulses do occur, they are typically caused by the forward directivity and/or permanent translation (fling) effects. 

Permanent translation (fling) is a consequence of permanent fault displacement due to an earthquake it appears in the form of step displacement and one-sided velocity pulse in the strike-parallel direction for strike-slip faults or in the strike-normal direction for dip-slip faults. In the latter case, directivity and permanent translation effects build up in the same direction. Figure 3 illustrates characteristic examples of permanent translation (fling) from the 1999 Izmit earthquake. The fault-parallel velocity and displacement time histories recorded at Yarimca (YPT) and Sakarya (SKR) stations are affected by the permanent displacement along the right-lateral strike-slip North Anatolian Fault. 

Seismic Actions Due to Near-Fauit Ground Motion, Fig. 4 Strong motion records with distinct velocity pulses (Reprinted from Mavroeidis and Papageorgiou (2003). Copyright 2003 Seismological Society of America)... 

The mathematical formulation for the representation of the near-fault ground velocity pulses proposed by Mavroeidis and Papageorgiou (2003) is the product of a harmonic oscillation with a bell-shaped function. That is ... 

The IDA approach cannot consider certain site-specihc ground motion conditions. As outlined by Baker (2013), some of the ground motion properties relevant for collapse assessment are the spectral shape of the elastic response spectrum, the duration, and the effects of near-fault ground motions and velocity pulses. The... 

The concepts of classical and quantum physics allow one, either exactly or with a certain probability, to predict the state of macrobodies or microparticles. In particular, this concerns mechanical movement regularities, which can be described by using spatial-temporal, coordinates, the vales of mass, velocity, pulse, wave characteristics, the knowledge of the fundamental t5q)e of interaction. However, there exist some processes whose features can be explained by neither classical physics nor quantum representations. E.g. the existence of bodies to them in different aggregation states, the appearance of elastic forces at deformations of systems, possible transformation of some compounds into others, etc. As a rule, these and similar processes are accompanied by transition of systems fi om one state to another one with changes in thermal energy. Just such processes and most general thermal properties of macroscopic bodies are studied by the section of physics and chemistry called thermodynamics [1, 2, 9-11]. 

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