Third order sensor

In this case, multiple species can be quantified and the baseline drift can be mathematically corrected. The third-order sensors thus belong to the category... 

Fig. 10.1 (a) First-order chemical sensor in which absorbance is uniquely related to concentration by calibration curve, (b) Second-order sensor in which absorbance is shown as a function of wavelength X. Interferant is easily identified in the spectrum, (c) Third-order sensor yielding information in 3-D space. The red dashed line shows conversion of third-order sensor to second-order sensor when the value of response R is obtained at a fixed retention time/ ... 

Fig. 10.3 Identification and quantification of the interferant by a third-order sensor in which optical, ion-selective electrode, and chromatographic data are combined (a) pure standards (b) contaminated sample...

The RI sensitivity, SKr, of the above sensor structure is given in Fig. 6.7. Whereas the sensitivity for the first-order mode increases monotonically with the increased wall thickness, the sensitivity for the second and third order modes oscillates significantly. In particular,, S Rr becomes nearly zero at certain regions that... 

Although less common, some third-order chemical sensors have found significant applications not only in sensing but also in research. One such example is Electrochemical Quartz Crystal Microbalance (EQCM). With EQCM, an electrochemical experiment can be performed in its inherently large experimental space, that is, various electrochemical waveforms, impedance analysis, gating, and different mass loading. As the dimensionality of the experiment is increased, so is its information content. 

Nevertheless, we still cannot identify which sensor is correct. For that, we need to go to the third-order level by performing, for example, a preseparation. If the two sensors are placed at the outlet of a chromatographic column, the signal for the pure sample is shown in Fig. 10.3a and the contaminated sample is shown in Fig. 10.3b. There, the retention time for pure standards Irs is different from the retention time for the interferant tfa, which strongly affects the response of the ISE but does not affect the optical sensor output to a significant degree. One such interference could be, for example, a different ionic strength of the unusual ... 

Among the third-order effects, of particular interest is the light intensity dependence of refractive index of the medium. This light control by light phenomenon, being an all-optical effect, provides the fastest photonic mechanism available. Another important application of photonics is derived from the intensity dependence of optical transmittance of materials. This phenomenon is the principle of optical power limiting used for sensor, human eye or electronic circuitry protection. The above two applications are the examples of the intensity dependent complex third-order optical susceptibility of a photonic medium. 

This transformation provides non-dimensional HSI values, where H is normalized with 2n and I is normalized with the maximum pixel count for an individual sensor of the digital camera (255 for each 8-bit sensor). Furthermore, the minimum and maximum hue and saturation values, respectively, detected in temperatures imder the red start temperature of the TLC material (25 °C) were used as a threshold level imder which the negative radian value of H would be used in order to obtain a better fit to a continuous third-degree polynomial function. 

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