State unstable

Gunton J D and Droz M 1983 Introduction to the Theory of Metastable and Unstable States (Berlin Springer)... 

In general, cavitation damage can be anticipated wherever an unstable state of fluid flow exists or where substantial pressure changes are encountered. Susceptible locations include sharp discontinuities on metal surfaces, areas where flow direction is suddenly altered (Fig. 12.5), and regions where the cross-sectional areas of the flow passages are changed. 

Anisotropic behaviour is also exhibited in optical properties and orientation effects can be observed and to some extent measured by birefringence methods. In such oriented materials the molecules are in effect frozen in an unstable state and they will normally endeavour to take up a more coiled conformation due to rotation about the single bonds. If an oriented sample is heated up the molecules will start to coil as soon as they possess sufficient energy and the mass will often distort. Because of this oriented materials usually have a lower heat distortion temperature than non-oriented polymers. 

Unstable state of plastic as evidenced by changes in physical )roperties not caused by the surroundings. Example is the temporary flexible condition some plastics display after molding. Assembly of all parts making up an injection mold, excluding cavity, cores and pins. 

Fermi and another European refugee, Leo Szilard, discussed the impact nuclear fission would have on physics and on the veiy unstable state of the world... 

The equilibrium is evidently stable when the entropy is a maximum, for then every possible change would diminish the entropy. The equilibrium will be unstable when the entropy is a minimum for a given value of the energy. This implies that if there are several conceivable neighbouring states with the same energy, that with the least entropy will correspond with a state of unstable equilibrium, whilst the others with more entropy will be essentially unstable states, except the one with the greatest amount of entropy, which will be the state of stable... 

The physical interpretation of this result is that, according to the conditions of pressure and temperature, the fluid to which the equation is applied can exist either in three states with different specific volumes at the same temperature and pressure, or else in only one state (imaginary roots having no physical significance). Case (ii.) corresponds to a gas heated above its critical temperature. In case (i.) the physical interpretation is that the smallest value of v corresponds to the liquid, the largest value of v corresponds to saturated vapour, and the intermediate value corresponds to an unstable state, all at the given temperature. 

Let us suppose that T and p are always given by equation (3), even on parts of the primitive surface which represent essentially unstable states. Then for motion from one point on that surface to another point we have ... 

Fig. 11. Hysteresis in the coil-to-stretch (CS) and stretch-to-coil (SC) transitions. For reversible situations, the transition from (S) to (C) should take place at a particular value of the strain rate (e ) through an unstable state (P). In practice, hysteresis is expected and should involve the cycle shown by arrows...

Metal ions in unusual and unstable states of oxidation and the steps of electrochemical reactions. B. G. Ershov, Russ. Chem. Rev. (Engl. Transl.), 1981, 50,1119-1133 (162). 

For an unstable electrode system, the asymmetrical fluctuations first become unstable, then cascadelike transitions to the unstable state of the symmetrical fluctuations occur, if possible. As shown in Eqs. (42a) and (42b), when the amplitude factor becomes positive for certain wave numbers, the fluctuations become unstable, and the pits start to grow. When the amplification factor is negative for all wave numbers without exception, the growth of pits is depressed. From Eq. (43), the amplitude... 

Figure 5.43. Program THERMPLO provides the graphical steady-state solution. The parameters in the program give two steady states and one unstable state.

The Mechanism of Structure Formation During the Induction Period of Crystallization from the Unstable State... 

On the basis of the above described studies, we propose a model for the structure formation mechanism during the induction period when a polymer is crystallized from the unstable state. Figure 24 shows a schematic diagram of... 

This problem is very important, but it is extremely difficult to make SAXS measurements at higher temperatures because the induction period becomes too short to observe the time evolution of SAXS intensities. For example, as was seen in Sect. 2.2, the induction period was only 100 s when the PET glass was crystallized even at 115 °C, 40 K higher than Tg, where a detailed analysis of the SAXS data was impossible. Of course, as the crystallization temperature approaches the melting temperature, the induction period is expected to become longer. However, as will be shown below, no characteristic peaks of SD could be detected in SAXS curves either. This is probably because the crystallization temperature was not in the unstable state, or the characteristic wavelength was much larger compared with the lower resolution limit of... 

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