Pressure attenuation

The minimum shock wave pressure that causes complete detonation of the explosive under test is a measure of shock sensitivity of the explosive and is determined with the help of a gap test . The principle of this test is to subject the explosive under test to the action of a shock wave of known pressure generated by means of a calibrated donor charge and a shock wave pressure attenuator. 

To estimate P, Mizutani el al. [36] assumed that the shock pressure attenuates with propagation distance according to the power law... 

In Eqn. (9.16), the partial pressures refer to those at the crack tip. They may be replaced by the partial pressures in the external environment if the relative pressure attenuation along the crack is the same for both gases. Because only the competitive... 

The gap test enables the determination of the minimum shock wave pressure that can cause complete detonation of the tested explosive. The explosive to be tested is subjected to the action of the shock wave of a known pressure. Such wave is generated by means of a booster and a shock wave pressure attenuator. Whether or not the shock wave caused the complete detonation of the explosive can be concluded on the basis of the mechanical effects produced after the detonation of the explosive hole cutting in a steel plate, dent depth in a witness steel block, or compression of a copper cylinder. 

A lead cylinder of a defined size (60 mm height and 40 mm diameter) and defined quality is placed on a massive st l base. A 10-30 mm thick and 41.5 mm in diameter steel disc is placed on the cylinder. The steel disc serves for the shock wave pressure attenuation. Its thickness depends on the brisance of the explosive. The 50 g of the tested explosive charge whose diameter is 40 mm is placed onto the steel disc. Afterwards, all the parts are fixed ly means of adhesive tape. 

Tai et al. adopted a high pressure attenuated total reflection Fourier transform infrared (ATR-IR) to investigate the interactions of CO2 with PLA and PLGA polymers with the glycolic add (GA) content in the copwlymers as 15, 25, 35 and 50 % respectively (Table 1). Shifts and intensity changes of IR absorption bands of the polymers in the carbonyl region ( 1750 cm i) are indicative of the interaction on a qualitative level. The sp>ectra for PdlLA... 

A pressure vessel must be well designed in order to ensure that changes in atmospheric pressure do not produce equivalent horizontal or vertical outputs. Three critical specifications, then, are pressure attenuation of the pressure vessel and the pressure sensitivities of the vertical and horizontal outputs. 

Fig. 9.30 Diagram of HAM deflagration pressure attenuation [7] 7 - 5.3 m container with HAM 2 - protective wall of 4 m in height and 10 m in width...

Fig. 9.32 Diagram of the facility for pressure attenuation resulting from a HAM detonation [17, 18] 7 - wall 2 - HAM...

TNT pressure equivalent of a gas explosion TNT impulse equivalent of a gas explosion Decrement of pressure attenuation behind a wave front Proportionality factor Tube length... 

So far the emphasis has been on substituting hazardous materials or using less, i.e., intensification. Let us now consider use of hazardous materials under less hazardous conditions, i.e. at less extreme temperatures or pressures or as a vapor rather than superheated liquid or diluted, in other words, attenuation. ... 

During the attenuation measurements. Transducer 1 was excited with a narrowband tone burst with center frequency 18 MHz, see Figure 1 for a schematic setup. The amplitude of the sound pressure was measured at Tranducer 2 by means of an amplitude peak detector. A reference amplitude, Are/, was measured outside the object as shown at the right hand side of Figure 1. The object was scanned in the j y-plane and for every position, (x, y), the attenuation, a x, y), was calculated as the quotient (in db) between the amplitude at Transducer 2, A[x, y), and Are/, i.e., a(x,y) = lOlogm Pulse echo measurements and preprocessing... 

I oise Transmission Reduction in HVACSystems. One common use of sound-absorbing treatment is to reduce noise transmission in heating, ventilating, and air-conditioning (HVAC) systems (6). The treatments ate used to reduce the transmission of fan noise and air turbulence noise through ducts into occupied spaces. Noise transmission reduction in duct systems is described in terms of insertion loss, the difference in sound power level or sound pressure level measured at a given location before and after installation of the treatment or sound attenuation, the reduction in sound power between two locations affected by a sound source. The units ate decibels. 

In general, once the curtain of filaments has been produced, it is necessary to attenuate the filaments in order to provide strength and resistance to deformation. The most commonly practiced approach is to utilize a single slot, which is at least the width of the curtain, at a point below the spinning plate and above the laydown screen. There are two practical approaches taken. The first utilizes the injection of low pressure air at a point above the slot so that the fibers attain sufficient acceleration in the slot to provide adequate draw (22) (Fig. 7). The second utilizes a low pressure vacuum below a venturi to provide the pressure differential requited for sufficient acceleration and resulting attenuation (30). 

One of the limitations of the curtain/slot draw process is that the amount of fiber attenuation is constrained due to the short distance generally allowed between the spinnerette and the venturi slot and the use of relatively low pressure air for drawing so as not to induce high turbulence in the area of the laydown. In practical terms this has made the process difficult to adapt for the production of polyester fabrics which inherently require much higher fiber acceleration to attain the desired polyester fiber properties. 

In the manufacture of meltblown fabrics, a special die is used in which heated, pressurized air attenuates the molten polymer filament as it exits the orifice of the dye or nozzle (Fig. 9). Air temperatures range from 260—480°C with sonic velocity flow rates (43). 

The attenuation of ultrasound (acoustic spectroscopy) or high frequency electrical current (dielectric spectroscopy) as it passes through a suspension is different for weU-dispersed individual particles than for floes of those particles because the floes adsorb energy by breakup and reformation as pressure or electrical waves josde them. The degree of attenuation varies with frequency in a manner related to floe breakup and reformation rate constants, which depend on the strength of the interparticle attraction, size, and density (inertia) of the particles, and viscosity of the Hquid. 

Liquid Level. The most widely used devices for measuring Hquid levels involve detecting the buoyant force on an object or the pressure differential created by the height of Hquid between two taps on the vessel. Consequently, care is required in locating the tap. Other less widely used techniques utilize concepts such as the attenuation of radiation changes in electrical properties, eg, capacitance and impedance and ultrasonic wave attenuation. 

Successive reflections of the pressure wave between the pipe inlet and the closed valve result in alternating pressure increases and decreases, which are gradually attenuated by fluid friction and imperfect elasticity of the pipe. Periods of reduced pressure occur while the reflected pressure wave is travehng from inlet to valve. Degassing of the liquid may occur, as may vaporization if the pressure drops below the vapor pressure of the liquid. Gas and vapor bubbles decrease the wave velocity. Vaporization may lead to what is often called liquid column separation subsequent collapse of the vapor pocket can result in pipe rupture. 

The stiffness characteristic of the positioner/actuator varies with frequency. Figure 8-75Z indicates the stiffness of the positioner/actu-ator is high at low frequencies and is directly related to the locked-stem pressure gain provided by the positioner. As frequency increases, a dip in the stiffness curve results Trom dynamic gain attenuation in the pneumatic amplifiers in the positioner. The value at the bottom of the dip is the sum of the mechanical stiffness of the spring in the actu-... 

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