Shock-wave

The dose resulting from the initial nuclear radiation depends in a complex way on the explosion power and on distance, and on the density variations of air due to the blast (the hydrodynamic increment due to the rarefaction of air behind the shock wave at high explosion energies). Tables 22-1 and 22-2 detail three values of gamma and neutron doses, respectively, and distance (in air from the explosion centre) for three typical explosion energies. Other values can be interpolated or extrapolated. The uncertainty is equal to a factor of two in both ways. 

Protection from the initial radiation is obtained by shielding layers. For gamma rays, every material is useful, but preferably those with a high atomic 

The pressure acting on a structure hit by the wave is not equal to the above mentioned peak pressure unless the structure is hit sideways, that is when the structure wall considered is parallel to the direction of propagation of the wave. In any other case, the maximum dynamic pressure on the wall is higher than the peak one by a factor of 2-4 (theoretically, 8) for a wall perpendicular to the wave direction of propagation, due to the reflection of the wave itself. 

Diagrams exist for the preventive evaluation of the possible damage to various structures, drawn on the basis of experimental and theoretical data. As an example, a reinforced concrete office building, designed to resist an earthquake, can be severely damaged by a 1 Mt explosion up to about 10 km distant. 

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Detonation. In a detonation, the flame front travels as a shock wave, followed closely by a combustion wave, which releases the energy to sustain the shock wave. The detonation front travels with a velocity greater than the speed of sound in the unreacted medium. 

The term detonation often employed to describe knocking is incorrect because the phenomenon can not be attributed to the propagation of a flame in the supersonic region, accompanied by a shock wave.. 

Glanzer K, Quack M and Tree J 1977 High temperature UV absorption and recombination of methyi radicais in shock waves 16th Int. Symp. on Combustion (Pittsburgh The Combustion institute) pp 949-60... 

Johnson Q and Mitchell A C 1972 First x-ray diffraction evidence for a phase transition during shock-wave compression Phys. Rev. Lett. 29 1369... 

B2.5.3.3 RELAXATION AFTER LARGE PERTURBATION SHOCK-WAVE EXPERIMENTS... 

Figure B2.5.6. Temperature as a fiinction of time in a shock-tube experiment. The first r-jump results from the incoming shock wave. The second is caused by the reflection of the shock wave at the wall of the tube. The rise time 8 t typically is less than 1 ps, whereas the time delay between the incoming and reflected shock wave is on tlie order of several hundred microseconds. Adapted from [110].

Figure B2.5.7. Oscilloscope trace of the UV absorption of methyl radical at 216 mn produced by decomposition of azomethane after a shock wave (after [M]) at (a) 1280 K and (b) 1575 K.

The pyrolysis of CR NH (<1 mbar) was perfomied at 1.3 atm in Ar, spectroscopically monitoring the concentration of NH2 radicals behind the reflected shock wave as a fiinction of time. The interesting aspect of this experiment was the combination of a shock-tube experiment with the particularly sensitive detection of the NH2 radicals by frequency-modulated, laser-absorption spectroscopy [ ]. Compared with conventional narrow-bandwidth laser-absorption detection the signal-to-noise ratio could be increased by a factor of 20, with correspondingly more accurate values for the rate constant k T). 

Sturtevant B, Shephard J E and Hornung H G (eds) 1996 Proc. 20th Int. Symp. on Shock Waves (Singapore World Scientific)... 

Tree J 1975 Shock wave studies of elementary chemical processes Modern Deveiopments in Shock Tube Research ed G Kamimoto (Japan Shock Tube Research Society) pp 29-54... 

Greene C H and Toennies J P 1964 Chemicai Reactions in Shock Waves (London Arnold)... 

Figure B3.3.13. Intersecting stacking faults in a fee crystal at the impact plane induced by collision with a momentum mirror for a square cross section of side 100 unit cells. The shock wave has advanced half way to the rear ( 250 planes). Atom shading indicates potential energy. Thanks are due to B Holian for tliis figure.

A laser beam is capable of putting so much energy into a substance in a very short space of time that the substance rapidly expands and volatilizes. The resulting explosive shock wave travels through the sample, subjecting it to high temperatures and pressures for short times. This process is also known as ablation. 

Shirakawa techmqi Shirlan Shirley Non-Lint AnalyZ Shi take mushroom Shock absorbers Shock absorption Shocking Shockley defects Shock treatment Shock tubes Shock waves Shoe components Shoe products Shoes... 

The iaterpretation of the spectroscopy of SBSL is much less clear. At this writing, SBSL has been observed primarily ia aqueous fluids, and the spectra obtained are surprisiagly featureless. Some very interesting effects are observed when the gas contents of the bubble are changed (39,42). Furthermore, the spectra show practically no evidence of OH emissions, and when He and Ar bubbles are considered, continue to iacrease ia iatensity even iato the deep ultraviolet. These spectra are reminiscent of blackbody emission with temperatures considerably ia excess of 5000 K and lend some support to the concept of an imploding shock wave (41). Several other alternative explanations for SBSL have been presented, and there exists considerable theoretical activity ia this particular aspect of SBSL. 

A great deal of experimental work has also been done to identify and quantify the ha2ards of explosive operations (30—40). The vulnerabiUty of stmctures and people to shock waves and fragment impact has been well estabUshed. This effort has also led to the design of protective stmctures superior to the conventional barricades which permit considerable reduction ia allowable safety distances. In addition, a variety of techniques have been developed to mitigate catastrophic detonations of explosives exposed to fire. 

Explosives are commonly categorized as primary, secondary, or high explosives. Primary or initiator explosives are the most sensitive to heat, friction, impact, shock, and electrostatic energy. These have been studied in considerable detail because of the almost unique capabiUty, even when present in small quantities, to rapidly transform a low energy stimulus into a high intensity shock wave. 

Other. Because a foam consists of many small, trapped gas bubbles, it can be very effective as a thermal insulator. Usually soHd foams are used for insulation purposes, but there are some instances where Hquid foams also find uses for insulation (see Eoamed plastics Insulation, thermal). Eor example, it is possible to apply and remove the insulation simply by forming or coUapsing the foam, providing additional control of the insulation process. Another novel use that is being explored is the potential of absorbing much of the pressure produced by an explosion. The energy in the shock wave is first partially absorbed by breaking the bubbles into very small droplets, and then further absorbed as the droplets are evaporated (53). 

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