Specific mass optical density

Instead of the specific optical density, the authors suggested that the optical density should be related to the mass of the material burnt away (mass optical density, MOD), It was theoretically and experimentally demonstrated that this value is less dependent on the thickness and density of the specimen. 

Ascertainment of smoke formation from a material is rather difficult due to the uncertainties in testing and evaluation. The measurement of smoke generation is to some extent dependent on the measurement technique i.e. whether smoke has been collected in a chamber or is streaming in a pipe whether gravimetric or optical evaluation is used and in the case of optical density, whether specific optical density, mass optical density, or a different measure is to be considered. 

BS 6401 [103] and ASTM E662 [104] are based on the NBS smoke test and are essentially the same test although some differences occur see Fig. 18. A 75 mm square specimen of up to 25 mm thick is combusted in a vertical orientation at 25 kW m incident heat flux. Tests are carried out with and without a scries of pilot flames along the lower edge of the specimen. The smoke is contained in a cabinet of 0.51 m and measured using a vertical photomultiplier lamp system. The results are typically expressed as specific optical density, which relates the optical density of the smoke to the volume of the cabinet, the length of the smoke-measuring path, and the area of the specimen exposed in the test. Other methods have been used in which specific optical density is related to the mass of the specimen combusted and/or to time. 

Nelson pointed out that smoke density was influenced not only by the burning area but also by the thickness of the specimen. Early melting of a material with a low melt viscosity may distort the experimental results. For this reason, the specific optical density related to unit mass of the burnt material, Djrrii, was put forward where is the maximum specific optical density and is the mass of the burnt proportion of the material. 

Both polymers were prepared following standard procedures. The PMMA sample had additionally 10 mol% of tetra-4-tert.butyl-phthalocyamin (dye molecule) because it was used in an early optical bole burning experiment [15]. For the specific heat and heat release measurements the mass and density of the PMMA sample were determined as 11.97 g and 1.15 g/cm, respectively. We have measured two PS samples prepared from different batches. The densities of these samples were 1.05 g/cm, and the masses 11.4 g (sample PSl) and 38.0 g (sample PS2). 

D is the maximum optical density and K is the average optical density over the size range under examination. If Km is assumed equal to unity, equation (5.9) gives the mass specific surface by photoextinction with no correction for the breakdown in the laws of geometric optics. 

A very common and useful approach to studying the plasma polymerization process is the careful characterization of the polymer films produced. A specific property of the films is then measured as a function of one or more of the plasma parameters and mechanistic explanations are then derived from such a study. Some of the properties of plasma-polymerized thin films which have been measured include electrical conductivity, tunneling phenomena and photoconductivity, capacitance, optical constants, structure (IR absorption and ESCA), surface tension, free radical density (ESR), surface topography and reverse osmosis characteristics. So far relatively few of these measurements were made with the objective of determining mechanisms of plasma polymerization. The motivation in most instances was a specific application of the thin films. Considerable emphasis on correlations between mass spectroscopy in polymerizing plasmas and ESCA on polymer films with plasma polymerization mechanisms will be given later in this chapter based on recent work done in this laboratory. 

Of course, the details of the gain spectra depend on the dimensionality of the active material (bulk, quantum well, etc.) and on the details of the band structure. For such detailed calculations we refer to Chapter A6 of this volume. However, it is important to note that due to the specific band structure of the nitrides, the carrier densities needed to achieve inversion and optical gain are very large compared to other m-V semiconductors. In particular, both the electron effective mass (nw = 0.22 [7]) as well as the hole effective mass (mi, 2.0 [8-10]) are three- to four-fold larger than in GaAs. For the same reason, however, the maximum gain obtainable from nitride structures is also larger. 

Both injection-type and optically pumped nitride-based semiconductor laser structures exhibit fairly high threshold pump levels compared to other III-V or II-VI semiconductors. This is fundamentally due to the specific band structure of the nitrides, i.e. the extremely large effective masses of both electrons and holes. The carrier densities needed to achieve transparency are of the order 2 x 1019 cm 3. 

The same information may be conveyed by quoting either the specific optical rotatory power a/yl, or the molar optical rotatory power a/cl, where y is the mass concentration, c is the amount (of substance) concentration, and l is the path length. Most tabulations give the specific optical rotatory power, denoted [a]2. The wavelength of light used X (frequently the sodium D line) and the Celsius temperature 0 are conventionally written as a subscript and superscript to the specific rotatory power [a]. For pure liquids and solids [a]2 is similarly defined as [a]J = a/pi, where p is the mass density. 

The rotation of the plane of polarized light is measured as an optical rotation a. What is termed the specific optical rotation [a] in organic chemistry is a function of the mass fraction W2 of the solute, the density of the solution p, and the length / of the sample cell, as well as the optical rotation ... 

Jell] [1936Jel2] Thermal analysis, optical microscopy, hardness measurements, specific density measurements Temperature-composition sections at 10, 25, 50, 70, 75 mass% and 3 to 12 mass% Cu Liquidus and solidus temperatures at 20 mass% Cu... 

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