Impedance definition

WATCHE (G.), LASNIER (J.), MANSIR (M.), BURAIS (N.), NICOLAS (A.), Definition d un logiciel adapte au calcul de I impedance d un capteur a courants de Foucault, CEDRAT recherche, 1985. 

The annular flow pattern discussed above shows a definite connection with burn-out, and enables a simple burn-out mechanism to be set forth. There are many other flow patterns referred to in the literature, however, and we will consider here what can be said about any connection they may have with burn-out. It does not follow that there must be a connection, as a flow pattern is essentially a description of the bulk conditions in a channel and depends upon the none-too-reliable results of visual observation, which is often impeded by optical distortion. Thus, although gross conditions may appear to change and one pattern give way to another, the hydrodynamic state prevailing close to the heated surface may remain practically unaffected and the burn-out mechanisms unaltered. 

In our opinion, the interesting photoresponses described by Dvorak et al. were incorrectly interpreted by the spurious definition of the photoinduced charge transfer impedance [157]. Formally, the impedance under illumination is determined by the AC admittance under constant illumination associated with a sinusoidal potential perturbation, i.e., under short-circuit conditions. From a simple phenomenological model, the dynamics of photoinduced charge transfer affect the charge distribution across the interface, thus according to the frequency of potential perturbation, the time constants associated with the various rate constants can be obtained [156,159-163]. It can be concluded from the magnitude of the photoeffects observed in the systems studied by Dvorak et al., that the impedance of the system is mostly determined by the time constant. 

Infrared spectroscopy is a major tool for polymer and rubber identification [11,12]. Infrared analysis usually suffices for identification of the plastic material provided absence of complications by interferences from heavy loadings of additives, such as pigments or fillers. As additives can impede the unambiguous assignment of a plastic, it is frequently necessary to separate the plastic from the additives. For example, heavily plasticised PVC may contain up to 60% of a plasticiser, which needs to be removed prior to attempted identification of the polymer. Also an ester plasticiser contained in a nitrile rubber may obscure identification of the polymer. Because typical rubber compounds only contain some 50% polymer direct FUR analysis rarely provides a definitive answer. It is usually necessary first... 

Comparable fuels. In order to promote the recycling of materials with high fuel values, certain materials that are burned as fuels are excluded from the definition of solid waste, provided that they meet certain specifications (i.e., are of a certain degree of purity). This is to ensure that the material does not exceed certain levels of toxic constituents and physical properties that might impede burning. Materials that meet this specification are considered comparable to pure or virgin fuels. 

The chemical world is often divided into measurers and makers of molecules. This division has deep historic roots, but it artificially impedes taking advantage of both aspects of the chemical sciences. Of key importance to all forms of chemistry are instruments and techniques that allow examination, in space and in time, of the composition and characterization of a chemical system under study. To achieve this end in a practical manner, these instruments will need to multiplex several analytical methods. They will need to meet one or more of the requirements for characterization of the products of combinatorial chemical synthesis, correlation of molecular structure with dynamic processes, high-resolution definition of three-dimensional structures and the dynamics of then-formation, and remote detection and telemetry. 

From our definition of a pure capacitor (i.e. one having no resistive component), we can say that the real impedance Z is zero. We see straightaway from equation (8.8) that the impedance is a function of frequency. The impedance of a capacitor is infinite when a DC voltage is applied (just put ru = 0 into equation (8.8)), while the imaginary impedance Z" decreases as the frequency co is increased. 

Progress in controlling marine pollution has been impeded by the difficulty of defining it. Two international advisory groups (the United Nations Group of Experts on the Scientific Aspects of Marine Pollution and the International Commission for Exploration of the Sea) have adopted the following definition ... 

While such one-to-one assignments of impedance features to specific reaction steps are appealing, it is not clear how definitive they are without further analysis. In particular, based on what we know about... 

With regard to innovation processes the significance and the direct effectiveness of individual committed promoters or blockers with their individual motives such as profit or occupational health and safety, consumer protection or environmental protection should, however, not be overestimated. Although committed promoters do play an important part in most substitution processes, a closer look at the individual case samples very quickly reveals their structural futility. Complex innovative processes cannot be moved by a limited number of actors or even by individuals alone. Many substitution processes simply do not progress, despite the fact that we cannot observe any definite opponents . These innovations are not impeded, they only become stuck, as the inertia of the system is simply too high. In order to gain an appropriate comprehension of the ability (and not just the... 

Chronopotentiometry, galvanostatic transients, 1411 as analytical technique, 1411 activation overpotential, 1411 Clavilier, and single crystals, 1095 Cluster formation energy of, 1304 and Frumkin isotherm, 1197 Cobalt-nickel plating, 1375 Cold combustion, definition, 1041 Cole-Cole plot, impedance, 1129, 1135 Colloidal particles, 880, 882 and differential capacity, 880 Complex impedance, 1135 Computer simulation, 1160 of adsorption processes, 965 and overall reaction, 1259 and rate determining step, 1260... 

Erdey-Gruz, 1048, 1306 1474 Erschler, 1133, 1134, 1425 Ethylene oxidation, anodic, 1052 1258 Exchange current density, 1049, 1066 correction of, 1069 definition, 1053 electrocatalysis and, 1278 impedance and, 1136 interfacial reaction, 1047 and partly polarizable interface, 1056 Excited states, lifetime, 1478 Exothermic reaction, 1041 Ex situ techniques, 785, 788, 1146... 

Semiconductors (cont.) equilibrium in. 1076 exponential law, 1081 germanium as, properties, 1076 hole movement 1076 impedance of, 1136 importance of, 785 limiting current 1088 n-, in thermal reactions, 1086 n-pjunction, 1073, 1081 p- in thermal reactions. 1086 photoactivity of, 1089 photoelec trochemistiy, 1073 photos timulated electrodeposition on. 1345 potential variation with distance in, 1082 silicon as, properties, 1076 surface states. 1086 symmetry factor in, 1082 thermal reactions, definition, 1088 Sen, 1495... 

Can observe surface terrain at 1-2-mn definition occasionally atomic resolution, in solution. AFM particularly useful in observation of biosurfaccs Can be programmed to recognize patterns of behavior characteristic of certain mechanism sequences. Computer simulation is vital in, e.g., impedance spectroscopy... 

In contrast to the chronocoulometric technique, the information obtained from the impedance technique concerns the derivatives with respect to potential of To, In /30 and d(ln (30)/dE. It is therefore needed to postulate an explicit isotherm in order to fit experimental data to the theoretical equations. However, the results, e.g. for (dT0/dE, can be integrated to give T0 as a function of potential within the faradaic region. As chronocoulometry is, by definition, applicable to potentials outside the faradaic region, the two methods may be considered as complementary tools to study adsorption phenomena that are hard to detect in the classical way, i.e. from double-layer data (e.g. the capacity Cd) that are influenced by the presence of electro-inactive absorbates. 

However, a dictionary definition of fouling includes to obstruct (with foreign matter), to entangle, to impede, while a foulant is described as fetid, stinking, and putrid. Thus the definition of foulant should, of necessity, include matter of microbiological origin, plus its degradation products. 

---