Transmission values

Thermal Insulation. Foamed plastics (qv) are used as thermal insulation for aU types of constmction because of their low heat- and moisture-transmission values. Polystyrene is used either as foamed board or expandable beads. The foam may be faced with a stmctural surfacing material, eg, a kraft liner-board, to form a panel for insulating mobile homes. These foams can dupHcate the appearance of wood and be used as trim. Foams can also be used as backing, for example, on aluminum siding, to provide heat and sound insulation. Foamed beads can be incorporated in concrete to reduce its density and provide some thermal insulation. 

The specialty class of polyols includes poly(butadiene) and polycarbonate polyols. The poly(butadiene) polyols most commonly used in urethane adhesives have functionalities from 1.8 to 2.3 and contain the three isomers (x, y and z) shown in Table 2. Newer variants of poly(butadiene) polyols include a 90% 1,2 product, as well as hydrogenated versions, which produce a saturated hydrocarbon chain [28]. Poly(butadiene) polyols have an all-hydrocarbon backbone, producing a relatively low surface energy material, outstanding moisture resistance, and low vapor transmission values. Aromatic polycarbonate polyols are solids at room temperature. Aliphatic polycarbonate polyols are viscous liquids and are used to obtain adhesion to polar substrates, yet these polyols have better hydrolysis properties than do most polyesters. 

This equation gives higher transmissivity values than those calculated with methods described earlier. Presumably, Lihou and Maund s transmissivity is to be used for conditions of low relative humidity, in which dust particles (haze) are the main cause of attenuation. A conservative approach is to assume = 1. 

Such measurement provides the magnitude of birefringence, but not its sign. In addition, identical transmission values will be observed for multiple birefringence orders, that is, whenever the optical path difference, dAn, becomes a multiple of X. The main interest of this method arises from its excellent time resolution, below 1 ms, that is readily achieved using a low-power (e.g., 5 mW) continuous-wave laser and a photodiode. If the sample is initially isotropic, it is possible to follow the birefringence order to obtain quantitative results. For improved accuracy, a second (reference) photodiode or a beam chopper and a lock-in amplifier can be used. 

There is, however, something unexpected about Figure 44-1 la-1. That is the decrease in absorbance noise at the very lowest values of S/N, i.e., those lower than approximately Er = 1. This decrease is not a glitch or an artifact or a result of the random effects of divergence of the integral of the data such as we saw when performing a similar computation on the simulated transmission values. The effect is consistent and reproducible. In fact, it appears to be somewhat similar in character to the decrease in computed transmittance we observed at very low values of S/N for the low-noise case, e.g., that shown in Figure 43-6. 

A limited number of aquifer pumping tests have been conducted within the perched zone. Two separate tests were conducted on a recovery well located in the southwestern portion of the refinery. Low transmissivity values of 100 and 150 gpd/ft were calculated. 

The transmission of detonation in a confined space (in a tube or shothole) is higher than in the open air. E.g. an ammonium nitrate explosive with 4% nitroglycerine which ordinarily has a transmission value of 10-15 cm, in a mortar gives the value 19-23 cm, according to T. Urbanski [70]. This author studied change of transmission as a function of density. The results for ammonium nitrate explosives are given in the diagram in Fig. 144. 

The decrease in transmission values with density beyond a certain value (density higher than 1.1) seems to be of particular significance. T. Urbanski showed as early as 1926 [70] that the shock wave produced by detonation of an explosive can move along a shothole, or a mortar, at a rate higher than the rate of detonation (e.g. 

Spectra were obtained with a Perkin-Elmer Model 13 spectrophotometer (double beam) modified to scan and record linearly in frequency [9]. A calibrated LiF prism was used with estimated frequency accuracy rh 4 cm"1. The spectral slit- width was about 9 cm "1 at 3600 cm"1 and 6 cm"1 at 3000 cm 1v Transmission accuracy is estimated at 0 5% in the region 30-50% T, where most measurements were made. The zero and 100% transmission values were measured for each spectrum, and a correction was applied for false energy. 

A somewhat more complicated method is frequently used to obtain "integrated intensity" values. The photograph is placed on a recording photometer, which provides a graphical record of the transmission along the center line of the diffraction maximum (or along a layer line of the diffraction transform). The ordinates of the trace are proportional to the transmission, T, while the abscissas are distances along the film. The transmission values are then converted to x-ray exposures. 

Protein transmission data (Fig. 8) indicate nearly 100% transmission of protein initially, but the fraction of protein transmitted decreased rapidly for forward filtration of a BSA-only solution and appeared to reach a steady value of only 35% transmission after 10,000 s. When a secondary membrane of yeast was deposited at the beginning of each cycle, and then filtration of a BSA solution was carried out, the protein transmission values remained at nearly 100% for about 4000 s and subsequently decreased gradually to about 60% after 18,000 s of filtration. With SMY, the amount of protein recovered in the permeate is more than two times that recovered after filtration of the BSA-only solution after 18,000 s. 

Bandpass filters can be described in several ways. Most common is the Center Wavelength (CWL) and Full Width Half Maximum (FWHM) nomenclature, or alternatively, by nominal Cut-on and Cut-off wavelengths. In the former, the exciter in Fig. 2 is described as a 580/20 or, a filter with nominal CWL of 580 nm and a FWHM of 20 nm. The half maximum value is taken at the transmission value where the filter has reached 50% of its maximum value (Figure 3). In the latter scheme, the filter would be described as having a Cut-on of 570 nm and a Cut-off of 590 nm, no CWL is declared. The Cut-on describes... 

According to the Lambert-Beer law, the absorbance can be related directly to the concentration of a compound in a sample. However, IR spectrometers usually record and present data in terms of percent transmission rather than in absorbance units. In these cases, the absorbance values, which are proportional to the logarithms of the respective transmission values (see Eq. 5.1-4), have to be calculated from the spectra. Absorbance measurements should be taken exactly for the band maximum. Even small errors in the reproducibility of the wavenumber setting causes considerable variations of the measured absorbance. In order to avoid errors due to the influence of the spectrometer function, it... 

The residual transmission of brown glass is recognized by both the European and the U.S. Pharmacopoeia. UV-VIS transmission values up to 10% are acceptable. In the case of parenteral preparations transmission values up to 50% are acceptable, depending on the product s fill volume. 

According to the Lambert-Beer s law, the absorption increases with the layer thickness. The higher the absorption, the better will be the photo protective properties of the container. Depending on the intended purpose the layer thickness of the glass container is limited to a certain extent. This fact is also considered in the pharmacopoeial tests for the transmission of colored glass containers, where higher transmission values are acceptable (3,4). 

Table 1 The percent transmission at three wavelengths of 10 solutions, (a), the correlation matrix of transmission values (b), and the mean transmission values as a row vector (c)...

Neural network methods require a fixed length representation of the data to be processed. Vibrational spectra recorded usually fulfill this requirement. With most applications in vibrational spectroscopy, the spectral range and resolution are fixed, and a comparison of spectra from different sources is directly possible. Appropriate scaling of the spectra allows handling different resolutions to obtain the same number of components in a descriptor. Digitized vibrational spectra typically contain absorbance or transmission values in wave-number format. Most of the spectrometers provide the standardized spectral data format JCAMP-DX developed by the Working Party on Spectroscopic Data Standards from the International Union of Pure and Applied Chemistry (lUPAC) [48]. 

Fig. 23 Linear plot of the transmission value at low energy (Tl) derived from a UV spectrometer, vs the values measured with the laser experiment (TH)- Two different fluences (1.11 J cm-2 and 44 mj creT2) are shown. The higher fluence represents the case of chro-mophore saturation, whereas the lower fluence shows the linear transmission behavior (see Fig. 28). REPRINTED WITH PERMISSION OF [Ref. 60], COPYRIGHT (1996) Springer Verlag...

Fig. 10. Variation in IR absorption with effective depth of penetration [126]. Irradiation time O 40 h 80 h. dei values measured in from each surface of the 22 mil film dashed lines represent transmission values.

The last point which will be examined in this subsection is that of extracting the true transmission values from a DAC experiment, in order to calculate the absorption-coefficient spectrum. In the case of a plane-parallel slab of sample with a thickness d, a refractive index n, and an absorption coefficient a which is immersed in a transparent medium with an index n and negligible absorption, the theoretical transmission in the absence of interference fringes is... 

Chemically deposited non stoichiometric cuprous sulfide films (Cui.gS) have been used as conducting layers as reported by Grozdanov et al. [50]. The films, deposited at 40 °C, present a resistivity of 2.10 Q.cm. In addition they present optical transmission values between 50 and 70% in the visible range for a 0.12 pm thick film. These properties have been used for ohmic contacts to ferroelectric films and transparent conducting coatings on polymers. These films can also be used as chemical sensors for Cu + ions. Note that due to the low deposition temperature polymer substrates can be used [61]. 

While it is possible to grow highly conductive, transparent films, the properties of doped Sn02 are not as good as doped 10203. This can be seen for films with resistivities of 1 mQ cm with rather low transmission values of 75-85 %. The analogous value for ITO is 90-95%. 

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