Advantage of characterization

The necessity of somewhat high solute concentrations for significant changes in r3 results in that essentially equilibria having a rather low stability constant can be studied. This provides the advantage of characterizing weak ion association complexes, such as were found in AgC104 solutions [112, 113]. 

The important advantage of characterizing a point on the surface by / and K instead of by R and R2 is that while R and Rj are only defined in certain directions, / and K are direction independent as long as R and R2 are chosen perpendicular to each other. 

A related advantage of studying crystalline matter is that one can have synnnetry-related operations that greatly expedite the discussion of a chemical bond. For example, in an elemental crystal of diamond, all the chemical bonds are equivalent. There are no tenninating bonds and the characterization of one bond is sufficient to understand die entire system. If one were to know the binding energy or polarizability associated with one bond, then properties of the diamond crystal associated with all the bonds could be extracted. In contrast, molecular systems often contain different bonds and always have atoms at the boundary between the molecule and the vacuum. 

Other than the obvious advantages of reduced fluorescence and high resolution, FT Raman is fast, safe and requires mmimal skill, making it a popular analytic tool for the characterization of organic compounds, polymers, inorganic materials and surfaces and has been employed in many biological applications [41]. 

The use of NMR spectroscopy to characterize copolymer microstructure takes advantage of this last ability to discern environmental effects which extend over the length of several repeat units. This capability is extremely valuable in analyzing the stereoregularity of a polymer, and we shall have more to say about it in that context in Sec. 7.11. 

The main advantages of the ms/ms systems are related to the sensitivity and selectivity they provide. Two mass analyzers in tandem significantly enhance selectivity. Thus samples in very complex matrices can be characterized quickly with Htde or no sample clean-up. Direct introduction of samples such as coca leaves or urine into an ms or even a gc/lc/ms system requires a clean-up step that is not needed in tandem mass spectrometry (28,29). Adding the sensitivity of the electron multiplier to this type of selectivity makes ms/ms a powerhil analytical tool, indeed. It should be noted that introduction of very complex materials increases the frequency of ion source cleaning compared to single-stage instmments where sample clean-up is done first. 

The primary advantage of the feedforward over the feedback control strategy is that corrective action is initiated before the controlled variable is upset. Feedforward control, however, has its own drawbacks, ie, variables used to characterize the disturbances must be measurable a model of the response of the controlled variable to the disturbance must be available (when the feedforward strategy is used alone, the control performance depends on the accuracy of the model) and the feedforward control strategy does not compensate for any disturbance not measured or modeled. 

Constraint control strategies can be classified as steady-state or dynamic. In the steady-state approach, the process dynamics are assumed to be much faster than the frequency with which the constraint control appHcation makes its control adjustments. The variables characterizing the proximity to the constraints, called the constraint variables, are usually monitored on a more frequent basis than actual control actions are made. A steady-state constraint appHcation increases (or decreases) a manipulated variable by a fixed amount, the value of which is determined to be safe based on an analysis of the proximity to relevant constraints. Once the appHcation has taken the control action toward or away from the constraint, it waits for the effect of the control action to work through the lower control levels and the process before taking another control step. Usually these steady-state constraint controls are implemented to move away from the active constraint at a faster rate than they do toward the constraint. The main advantage of the steady-state approach is that it is predictable and relatively straightforward to implement. Its major drawback is that, because it does not account for the dynamics of the constraint and manipulated variables, a conservative estimate must be taken in how close and how quickly the operation is moved toward the active constraints. 

Equation 7 shows that as AP — oo, P — 1. The principal advantage of the solution—diffusion (SD) model is that only two parameters are needed to characterize the membrane system. As a result, this model has been widely appHed to both inorganic salt and organic solute systems. However, it has been indicated (26) that the SD model is limited to membranes having low water content. Also, for many RO membranes and solutes, particularly organics, the SD model does not adequately describe water or solute flux (27). Possible causes for these deviations include imperfections in the membrane barrier layer, pore flow (convection effects), and solute—solvent—membrane interactions. 

Water Consumption and Effluent Characterization. Another advantage of CGCC power generation is derived from lower water requirements. Because more than half of the power generated in a CGCC plant comes from the gas turbine, the water requirement is only 70—80% of that required for a coal-fired power plant, where all of the power is generated from steam turbines. 

Vacuum systems (Fig. 21-12h) are characterized by material moving in an air stream of pressure less than ambient. The advantages of this type are that all the pumping energy is used to move the product and that material can be sucked into the conveyor line without the need of a rotaiy feeder or similar seal between the storage vessel and the conveyor. Material remains suspended in the air stream until it reaches a receiver. Here, a cyclone separator or filter (Fig. 21-12c) separates the material from the air, the air passing through the separator and into the suction side of the positive-displacement blower or some other power source. 

Modulation Spectroscopy has proven to be an important characterization method for semiconductors and semiconductor microstructures. The rich spectra contain a wealth of information about relevant materials, surfaces and interfrces, as well as device characteristics. In general, the apparatus is relatively simple, compact (except EBER), inexpensive (except EBER), and easy to use. One of the main advantages of Modulation Spectroscopy is its ability to perform relevant measurements at room... 

The flow profiles of electrodriven and pressure driven separations are illustrated in Figure 9.2. Electroosmotic flow, since it originates near the capillary walls, is characterized by a flat flow profile. A laminar profile is observed in pressure-driven systems. In pressure-driven flow systems, the highest velocities are reached in the center of the flow channels, while the lowest velocities are attained near the column walls. Since a zone of analyte-distributing events across the flow conduit has different velocities across a laminar profile, band broadening results as the analyte zone is transferred through the conduit. The flat electroosmotic flow profile created in electrodriven separations is a principal advantage of capillary electrophoretic techniques and results in extremely efficient separations. 

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