Input/output devices 276 Subject

Thermodynamics has logged numerous equations of state over the years of the empirical variety. The common thread is their economy and intuition, where only a few parameters are called upon to address a constellation of forces. As the equations entail multivariable functions, they accommodate the tools of first-year calculus and, in turn, the infrastructure presented in Section 3.1. In their most basic applications, they enable conversions of independent variables into dependent ones. This is the subject of Figure 3.6. The ideal gas and van der Waals equations are represented as input-output devices. The devices accept n, T, V, measured for a gas such as argon and generate p in return. At 200 K, 0.00150 meter 2.00 moles, the van der Waals equation, with the help of Table 3.3 data, offers p = 2.07 x 10 pascals, while the ideal gas law delivers p - 2.22 x 10 pascals. The values differ because the nonideality is addressed, at least in part, by one device and not the other. The result is that the van der Waals equation better approximates the location of what will be termed the state point of the system the placement of a point in a coordinate plane such as pT. The state point placement is represented schematically in the lower half of Figure 3.6. 

Figure 1.1 Overview of the basic philosophy used in the development of perceptual audio quality measurement techniques. A computer model of the subject is used to compare the output of the device under test (e.g. a speech codec or a music codec) with the ideal, using any audio signal. If the device under test must be transparent then the ideal is equal to the input.

The perceptual model as developed in this chapter is used to map the input and output of the audio device onto internal representations that are as close as possible to the internal representations used by the subject to judge the quality of the audio device. It is shown that the difference in internal representation can form the basis of a perceptual audio quality measure (PAQM) that has a high correlation with the subjectively perceived audio quality. Furthermore it is shown that with a simple cognitive module that interprets the difference in internal representation the correlation between objective and subjective results is always above 0.9 for both wideband music and telephone-band speech signals. For the measurement of the quality of telephone-band speech codecs a simplified version of the PAQM, the perceptual speech quality measure (PSQM), is presented. 

The topic of this chapter may seem like a digression from methods and approaches to reaction mechanisms, but it is not it is an introduction to it. We worked on both topics for some time and there is a basic connection. Think of an electronic device and ask how are the logic functions of this device determined Electronic inputs (voltages and currents) are applied and outputs are measured. A truth table is constructed and from this table the logic functions of the device, and at times some of its components, may be inferred. The device is not subjected to the approach toward a chemical mechanism described in the previous chapter, of taking the device apart and testing its simplest components. (That may have to be done sometimes but is to be avoided if possible.)... 

The subject of analysis in this section is the Device evaluation fuzzy model. Its diagram is presented in Figure 2. The output of the fuzzy reasoning system (y associated with this fuzzy model is dependent on four input variables Detectability(x ), TIP evaluation yf Number of detection lines (x ), Device age (x ). 

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