Solid transmittance

Where heat is conducted through a plane solid which is between two fluids, there will he the convective resistances at the surfaces. The overall heat transfer must take all of these resistances into account, and the unit transmittance, or U factor, is given hy ... 

The DAC system consisted of computer, interface cards, meters, transmitters, and solid state relays (SSR). Electrodes of pH (Ingold), Oxidation-Reduction Potential (Cole-Parmer), and Dissolved Oxygen (Ingold) were installed and connected to individual meter. The status of reactor and the value of electrode signal were displayed in a computer monitor, and stored in data file. 

Figure 1.1. Schematic diagram of instrumentation associated with a fermentor. The steam sterilization system and all sensors and transmitters are omitted for clarity. Solid lines represent process streams. Hairlines represent information flow.

The basic components of the solid state spectrometer are the same as the solution-phase instrument data system, pulse programmer, observe and decoupler transmitters, magnetic system, and probes. In addition, high-power amplifiers are required for the two transmitters and a pneumatic spinning unit to achieve the necessary spin rates for MAS. Normally, the observe transmitter for 13C work requires broadband amplification of approximately 400 W of power for a 5.87-T, 250-MHz instrument. The amplifier should have triggering capabilities so that only the radiofrequency (rf) pulse is amplified. This will minimize noise contributions to the measured spectrum. So that the Hartmann-Hahn condition may be achieved, the decoupler amplifier must produce an rf signal at one-fourth the power level of the observe channel for carbon work. 

Figure 2. Detection range for an FM radio transmitter at Wrotham in south-east England and a receiver at UCL. The solid contour represents a signal-to-noise ratio of 15dB.

The factor (q/a ) may be obtained from independent optical and geometrical measurements, since q is the transmittance of the attenuator used for the incident beam, a is the solid angle of detection of scattered light and is the thickness of sample. 

Fig. 2. Density of states, transmission and transmittance for the six site chain, as described in the text. The scaled state density (solid black line) exhibits resonances arising from eigenstates on the bridge. The transmittance (solid gray line) drops beyond the limits of the band, and shows only minimal oscillations within the band itself. The behavior of the overall resulting transmission function (dashed line) is determined by the scaled DOS within the band, and by the transmittance outside of the band.

If the nonlinear inerease of the reffaetive index is elose to its linear eontrast, the transmittanee of the strueture B ean be less or greater than its linear transmittanee depending on a, ai (P = 3, solid line in Fig. 16). If the nonlinear inerease of the refraetive index is greater than its linear contrast, the transmittance of the strueture B is always greater than its linear transmittanee (P = 5, dashed line in Fig. 16). In the limit of very intensive light beams (P > 20) the transmittanee is total, = 1 (dotted line in Fig. 16). 

Spectra of solid samples are usually recorded in the units of reflectance (R) or percent reflectance (%/ ), which is analogous to percent transmittance in that reflectance equals the ratio of the reflected radiation to the incident radiation. With diffuse reflectance, the reflected signal is attenuated by two phenomena absorption (coefficient k) and scattering (coefficient s). Lollowing the Kubelka-Munk theory, these two coefficients are related to the reflectance of an infinitely thick sample, by... 

Transmittance and reflectance data are used in color measurements. Transmittance spectra are used for liquid color measurements, while reflectance spectra are used on solid samples (powders, surfaces) and on opaque liquids (paint). A large number of color scales are in use today. Some are specific to a particular industry, while others enjoy broader application. The most common scales are the CIE L a b (Commission... 

NIR spectroscopy is probably the most successful technique for the development of qualitative and quantitative methods in the pharmaceutical industry. NIR spectra contain both chemical and physical information from samples (solid and liquid). Spectra can be acquired off-line in three different modes transmittance, reflectance and transflectance. In all cases, the spectra are obtained in a few seconds without or minimum sample pretreatment. Multivariate data analysis techniques are usually needed for the development of the... 

Fig. 7.1 Transmittance and reflectance spectra of In203 films. Broken lines undoped Iri203 solid hues ITO (10% Sn). (Adapted from Ref 17.)...

Fig. 7.3 Transmittance and reflectance spectra of ZnO films. Broken fines ZnO solid lines ZnO Al (4 at.%). (Adapted from Ref. 52.)...

Modern infrared (IR) spectroscopy is a versatile tool applied to the qualitative and quantitative determination of molecular species of all types. Its applications fall into three categories based on the spectral regions considered. Mid-IR (MIR) is by far the most widely used, with absorption, reflection, and emission spectra being employed for both qualitative and quantitative analysis. The NIR region is particularly used for routine quantitative determinations in complex samples, which is of interest in agriculture, food and feed, and, more recently, pharmaceutical industries. Determinations are usually based on diffuse reflectance measurements of untreated solid or liquid samples or, in some cases, on transmittance studies. Far-IR (FIR) is used primarily for absorption measurements of inorganic and metal-organic samples. 

Photometric accuracy is determined by comparing the difference between the measured absorbance of the reference standard materials and the established standard value. Many solid and liquid standards are commonly used to verify the photometric accuracy of a spectrophotometer. An optically neutral material with little wavelength dependency for its transmittance/absorbance is desirable because it eliminates the spectral bandwidth dependency of measurements. The advantages and disadvantages of various commonly used photometric accuracy standards are summarized in Table 10.6. Even for a relatively stable reference standard, the intrinsic optical properties may change over time. Recertification at regular intervals is required to ensure that the certified values of the standards are meaningful and accurate for the intended use. 

---