Positive phase impulse

The incident positive phase impulse in psi-ms outside a suppressive shield is given by (Ref. 38)... 

In Figure 3.1, the time over which the blast wave overpressure lasts is referred to as the positive phase duration, or simply duration. The area under the pressure-time curve is the impulse of the blast wave. Consequently, the positive phase impulse, I0, is defined as follows ... 

E = positive phase impulse, or mass moment of inertia... 

That portion below pQ is called the negative phase. Positive specific impulse, defined by... 

All flow behind the wave is stopped, and pressures are considerably greater than side-on. The pressure in normally reflected waves is usually designated pr(t), and the peak reflected overpressure, Pr. The integral of overpressure over the positive phase, defined in Equation (13), is the reflected specific impulse ir. Durations of the positive phase of normally reflected waves are almost the same as for side-on waves, thigh explosive blast sources than have most blast parameters. 

The Lovelace work was later converted in Ref. 46 to scaled curves for combinations of peak incident overpressure and positive phase specific impulse. These curves are reproduced here as Fig. 40. Hirsch s work (Ref. 44) can also be given as pressure-impulse combinations for ear injury, and this also was done in Ref. 46. 

Peak side-on positive overpressure, P, , positive phase duration, tj, and the corresponding positive impulse, In. 

In the above fig of a typical blast wave, peak pressure is the press increase at the shock front or the highest press in the wave minus atmospheric press, and is a measure of the max force exerted by the blast wave. Impulse is mathematically equal to rhe positive phase and is a measure of the force multiplied by the duration. The negative phase iasts considerably longer than the positive phase but the max negative press is only a fraction of the max positive press (See Ref 12,p 65ff)... 

It should also be mentioned that there are a number of empirical expressions (Held, 1983, 1990 Lehmann, 1973) that one can use to calculate, with certain accuracy, the shock wave parameters such as shock wave pressure in different materials, shock wave velocity, pressure positive phase duration, and shock wave impulse. 

Fig. 3 Impulse of the positive phase as a function of reduced radial distance.

A typical pressure history at a fixed point at some distance firom a TNT blast is shown in Figure 3.2. The important parameters are the peak side-on overpressure (or simply peak overpressure), p , the arrival time, the positive phase duration time, and the overpressure impulse, which is defined as the area under the positive duration pulse. 

Impulse The area under the overpressure-time curve for explosions. The area can be calculated for the positive phase or negative phase of the blast. 

FIG. II-2. Side-on blast parameters for TNT. W charge mass (kg) R distance (m) P peak positive incident pressure (Pa) T duration of positive phase of incident pressure wave (s) t time of arrival of blast wave (s) i incident impulse (pascal seconds/kg ) Z range/mass to the 1/3 power (m/kg ). 

Blast effect is measured by two criteria, peak pressure and impulse. Peak pressure is the pressure increase at the shock front or the highest pressure in the shock wave minus atmospheric pressure. Impulse is mathematically equal to the area under the time pressure curve for the duration of the positive phase (figure 4-9). This is approximately half the peak pressure multiplied by the duration of the positive phase. Peak pressure represents a measure of the maximum force exerted against a surface by a blast wave, since force is equal to the product of pressure and area. Impulse represents a measure of the force multiplied by the duration. 

Fig. 10.1 The measurable parameters of blast wave - time of arrival t+ - positive phase duration T - rarefaction wave duration SP ax overpressure wave ampUtude bJ - rarefaction wave amplitude / - compression phase impulse / - rarefaction phase impulse A/ 2 and T2 - secondary pressure rise and its duration...

Now, let us describe the impulse and time parameters of a gas detonation blast wave. According to [8-11] the positive phase pressure impulse /+ value and the... 

Fig. 10.7 Blast wave positive phase relative amplitude (a) and non-dimensional scaled impulse (b) versus non-dimensional scaled distance. Bands of parameter values contain experimental and calculation data [2, 3, 11,17, 20, 21, 26, 27, 32]...

The most important blast-wave parameters are peak overpressure and positive impulse i, as shown in Figure 6.11. The deep negative phase and second shock are clearly visible in this figure. 

The so-called "positive impulse in a shock wave is the area under the pressuretime curve "Phases of a Shock Wave represented as shaded area in Fig 15, p 51... 

Ultimately, the motor end-plate membrane gets repolarized inspite of the continued presence of the drug substance by virtue of a shift in receptor conformation. Though the membrane is normally poised for a new lease of depolarization, yet ACH and the motor nerve impulses do not succeed to evoke an appreciable response. Perhaps, this could be due to the fact that the nicotinic receptor is not positioned in its desired configuration. It has also been observed that during this critical phase, the neuromuscular blockade usually occurs specifically on certain characteristic features of competitive blockade and this may even get antagonized partially by the aid of anticholinesterases. 

Furthermore, the rotational impulse overcomes the breakaway torque and the linear impulse reduces pre-tension in order to ease loosening. The loosened screw is now unscrewed by a pneumatic drive and the impact mass is pushed to the starting position (Seliger and Wagner 1996). In case a screw cannot be released due to influences in the use phase (e.g., corrosion or dirt), the end effector can be used as a hollow drill with wide edges in order to remove the screw head. 

Once this eutoff has been found, we proeeed to find a more accurate estimation of the pitch using only the lower part of the signal. This is now possible as we are not attempting to pitch track noise. The amplitudes and phases are now foimd from Equation 14.5 as before, by minimising the error between the real and synthetic waveforms. This search can be performed in a number of ways Stylianou presents a fast technique for minimising Equation 14.5 directly [420], The noise component essentially has two parts h t) which describes the impulse response of the noise (which describes the spectrum of the noise envelope when transformed to the Frequency domain), and e t) which describes the sub-frame time evolution of the noise. For each fiame, h t) is found in a manner similar to linear prediction and e t) is estimated indirectly by calculating several values of h t) at shifted positions within the frame. 

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