Forming Dynamic Characteristics

The forming process (i.e., the first OFF-ON transition) does not occur instantaneously when a voltage step or pulse is applied to the a-Si p+-n-i device. Initially there is a delay time tD during which the device current remains essentially constant at the OFF-state value appropriate to the voltage across the device. Only after this delay does the current begin to increase, and it then rises almost instantaneously to its ON-state value. The forming delay time is an extremely sensitive function of the applied forming 

The results plotted in Fig. 5 for F CR correspond of course to voltages less than the point of instability indicated in Fig. 2a. There does appear to be a lower limit to the forming voltage, however, and present results indicate that the limiting voltage coincides with the bias at which the I- V characteristics change from their ohmic to nonohmic behavior (see Fig. 2b). Several 

Preliminary experiments have been carried out to determine the effects of device geometry on the forming voltage VF. It was found that VF increases linearly with the thickness dn of the n layer. Data for typical p+-n-i devices are plotted in Fig. 6. In this case VF was measured by applying a voltage ramp and its value coincides with the voltage VCR indicated in Fig. 5. It can be seen that the results do not extrapolate to zero voltage for zero n layer thickness. 

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Dynamic Effects. Particles often differ in their residence, inertia, and other dynamic characteristics which can cause them to segregate, particularly when they are forming a pile such as when charged into a bin or discharged from a chute. 

The aim of dynamic simulation is to be able to relate the dynamic output response of a system to the form of the input disturbance, in such a way that an improved knowledge and understanding of the dynamic characteristics of the system are obtained. Fig. 2.1 depicts the relation of a process input disturbance to a process output response. 

It may also be the case that the pharmacodynamic effect of a drug is exerted by both the parent compound and its metabolite(s), which implies that both should be included in the PK-PD model. Also, a drug may exist in two chiral forms with different kinetic and dynamic characteristics. 

A transient at 78 amu is also observed since it has the same dynamic characteristics seen for the 79 transient species it may be ascribed to fragmentation of the m/z = 79 cation formed by ionization of the cyclohexadienyl radical induced by the probe pulse. 

Let us consider that the solvent has nonoverlapping domains that have distinct static and dynamic characteristics. The diffusion in such a system can be considered as a random walk in a random environment formed by the independently relaxing domain [95], Hence the diffusions in three dimensions is the weighted average of the diffusion in all these different domains [84], The average diffusion D can then be written as... 

The kinetics of the recombination of Chl+ and MV+ radical ions formed during the quenching of 3Chl, consists of the fast and slow stages. The corresponding rate constants also occurred different at the inner and outer surfaces of the vesicles. The observed difference in the recombination rates was explained by different structural and dynamic characteristics of the inner and outer monolayers of the membrane. 

Let us deal with the transient response method. The transient response method is a method of measuring the characteristics of a system in particular, this method is effective when the dynamic characteristics of the system are investigated. In order to clarify the characteristics of the system, a comparison between the input and the output wave forms is useful. In general, the following three input wave forms have been widely used (Figure 2.1) ... 

Dynamic characteristics of -> phase transitions upon intercalation after application of an infinitely small potential step may include a slow process of -> nucleation and the growth of primary droplets of a new phase (more concentrated with the inserted ions) at the boundary with the solution electrolyte. After that, a continuous boundary of the new phase is formed, which moves into the host s interior in a diffusion-like manner. This process can be formally described in terms of a moving... 

The dynamic characteristics of adsorbed molecules can be determined in terms of temperature dependences of relaxation times [14-16] and by measurements of self-diffusion coefficients applying the pulsed-gradient spin-echo method [ 17-20]. Both methods enable one to estimate the mobility of molecules in adsorbent pores and the rotational mobility of separate molecular groups. The methods are based on the fact that the nuclear spin relaxation time of a molecule depends on the feasibility for adsorbed molecules to move in adsorbent pores. The lower the molecule s mobility, the more effective is the interaction between nuclear magnetic dipoles of adsorbed molecules and the shorter is the nuclear spin relaxation time. The results of measuring relaxation times at various temperatures may form the basis for calculations of activation characteristics of molecular motions of adsorbed molecules in an adsorption layer. These characteristics are of utmost importance for application of adsorbents as catalyst carriers. They determine the diffusion of reagent molecules towards the active sites of a catalyst and the rate of removal of reaction products. Sometimes the data on the temperature dependence of a diffusion coefficient allow one to ascertain subtle mechanisms of filling of micropores in activated carbons [17]. 

In order to determine the dynamic characteristics of an unknown system, the control engineer uses or induces certain forms of disturbances or inputs and observes or interprets their effects or outputs. Two of the most useful types of inputs for the study of process dynamics are the step function and the sine wave. 

We can now collect together the various characteristics of a measurement system, except for hysteresis, and express the general model for the system in the form of a block diagram. Such a block diagram representation is shown in Figure 4. The dynamic and static characteristics are shown decoupled in the diagram. The dynamic characteristics will be discussed shortly. 

Modified forms of these displays have been developed - e.g., the dye display which has a pleochroic dye dissolved in the nematic material and requires the use of just one polarizer - but we shall not be discussing them here. Analytical expressions have been derived which simplify the computational effort involved in optimizing the material and device parameters, but one has to rely on numerical modelling to give a complete description of the dynamical characteristics of these devices. Certain unusual dynamical effects observed in the TN device, e.g., the reverse-... 

Scale-up data of conventional SBDs are well known, but the relations cannot be applied to MSB dryers with inert packing due to different hydro-dynamical and drying characteristics. Therefore, the drying mechanism itself, effects of various process and operational parameters, and the relevant relationship had to be investigated in more detail. Important dimensions as well as geometric, physical, and hydro-dynamical characteristics of equipment and of the particles forming the spouted bed are summarized in Table 15.3 [18-20]. 

The normal mode analysis of IPMC diaphragm was performed for the optimal electrode case in order to investigate its dynamic characteristics. For the calculation, the density of Nafion in Li form was 2.078 x 10 kgm. The density of IPMC in Li was assumed to be 2.5 x lO kgm. The computed first (i.e. fundamental) and second natural frequencies were 430 and 1659 Hz, respectively. Given that the driving frequency range of the IPMC diaphragm is less than 40 Hz, the calculated fundamental frequency... 

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