Physical characteristic

Ventilation noise originates primarily from fans and the air turbulence generated inside ducts and around supply air and exhaust air terminal devices. The appearance of the noise is, of course, affected by factors such as the speed of rotation and the power of the fan, and by how the fan is stabilized or in other ways acoustically insulated. The noise level and the frequency characteristics are also largely derermined by the velocity of the air inside ducts and around terminal devices, where factors such as the dimensions and appearance of the ducts and terminal devices may play a decisive role in the appearance of the noise. 

The description of the physical characteristics of ventilation noise is based on more reliable knowledge than the description of the human effect. Misconceptions about the levels and frequency characteristics of ventilation noise are still common. This in turn has sometimes led to wrong suggestions about the measures that should be taken in order to eliminate the effects of a ventilation noise exposure. 

The links between levels of exposure and inconvenience caused by ventilation noise are described in an investigation carried out on office workers.- Technical measurements and analyses of the ventilation noise at 155 typical office workplaces were in this study combined with assessments by the office workers of the level of disturbance that they experienced, the effect on working performance, fatigue, stress-related pain, and headaches. The average noise level was about 40 dB(A) at two of the workplaces, while it was about 35 dB(A) at two others. It emerged from rhe narrow-band analyses that the sound pressure levels of rhe infrasound were not in any event of an order that this type of sound frequencies (below 20 Hz) could contribute to any disturbance effects. Any steps taken to counter the sound frequencies of the ventilation noise under 50 Hz, i.e., the point of btersection between the threshold curve of auditory perception and the spectral level distribution curve of 

4 VENTILATION NOISE-CHARACTERISTICS, EFFECTS, AND SUGGESTED COUNTER-MEASURES 

It should also be pointed out that the levels from ventilation noise in, for example, workshop premises are often lower than those emanating from other sources, for example machines of various kinds. It is not uncommon for the ventilation noise from industrial premises to cause more disturbance in adjacent offices than in the industrial premises themselves. The fact that ventilation noise propa gates in this manner is due to its pronounced low-frequency character. The more low-frequency components in the noise, the greater the propagation. Sound radiation from industrial premises, via duct openings in facades and roofs, may in this manner also cause disturbances in nearbv residential accommodations. 

Slightly soluble in water, soluble 1 in 9.5 of ethanol, 1 in 2 of chloroform, 1 in 15 of ether, 1 in 4 of isopropanol, 1 in 5.3 of methanol and 1 in 9 of propylene glycol. Freely soluble in acetone and in dimethylformamide, protect from light [13]. 

Soluble 1 in 6250 of water, 1 in 312 of alcohol, 1 in 75 in methanol, 1 in 525 of chloroform, 1 in 1408 of isopropanol, 1 in 119 of propylene glycol, freely soluble in dimethylsulfoxide, protect from light [1-3], 

Scattering angle 20 d- spacing (A) Relative intensity (%) Scattering angle 20 J-spacing (A) Relative intensity (%) 

The differential scanning calorimetry (DSC) thermogram of miconazole was obtained using a DuPont 2100 thermal analyzer system. The thermogram shown in Fig. 2 was obtained at a heating rate of 10°C/min and was run over the range 50—300 °C. Miconazole was found to melt at 186.55 °C. 

The ultraviolet absorption spectrum of miconazole nitrate in methanol (0.0104%) shown in Fig. 3 was recorded using a Shimadzu Ultraviolet-visible spectrophotometer 1601 PC. The compound exhibited three maxima at 264, 272, and 280 nm. Clarke reported the following Methanol 264 and 272 nm = 17a), 282 nm [2]. 

6 g cm l The density of organic matter is approximately 1 g cm . The hydroperiod and water-table fluctuations influence the air-filled pore space of soils, which are extremely important for oxygen diffusion into the soil from the atmosphere (soil aeration). 

FIGURE 3.4 Soil type and the hydrologic conditions influence the relative proportion of air and water per unit volume of soil (Patrick, 1973). 

FIGURE 3.5 Wetland soils under different hydrologic conditions. 

Besides restricting the supply of oxygen, excess water causes other important effects in wetland soils. Some of these effects are  

Softening of the soil material as a result of the weakening effect of water on the bonds holding soil particles together as stable aggregates. This physical effect can have several consequences  

We already defined it. Here we will consider it in relationship with the expansion coefficient of the materials to be bonded. If we have 2 materials with different coefficients of expansion, the adhesive film or sealant joint will be stressed when 

Adhesives are based on various polymers which have very different behaviors when submitted to heat. All adhesives will soften when the temperature reaches their softening point, but some adhesives will start to soften at 60°C such as the thermoplastic adhesives (vinyls, EVA hot melts), others at 70-80°C (neoprene and rubber based) the thermosetting adhesives will not soften until 90-150°C. 

Adhesives, based on polymers, do not melt sharply at a given temperature like some chemicals, but instead they soften gradually when the temperature rises, as is shown in Fig. 15. Before the temperature reaches the softening zone, the adhesive becomes softer and may creep under moderate loads. 

The heat resistance of the various adhesives will be indicated in the chapters dealing with these adhesives in this Handbook. Heat resistance may be evaluated by measuring mechanical properties at various temperatures. For example, the standard ASTM D 2295 allows one to measure the strength properties of adhesives in shear by tension loading at elevated temperatures. Heat resistance may be also measured by DSC analysis as indicated in Fig. 44 

Heat exposure of bonded parts varies greatly according to the applications and industries, for example  

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The complexity of petroleum products raises the question of sample validity is the sample representative of the total flow The problem becomes that much more difficult when dealing with samples of heavy materials or samples coming from separations. The diverse chemical families in a petroleum cut can have very different physical characteristics and the homogeneous nature of the cut is often due to the delicate equilibrium between its components. The equilibrium can be upset by extraction or by addition of certain materials as in the case of the precipitation of asphaltenes by light paraffins. 

The density and the volatility, expressed by the distillation curve and the vapor pressure, constitute the most important physical characteristics of motor fuels for obtaining satisfactory operation of a vehicle in all circumstances. 

The procedure for determining the cetane number in the CFR engine is not extremely widespread because of its complexity and the cost of carrying it out. There also exist several methods to estimate the cetane number of diesel fuels starting from their physical characteristics or their chemical structure. 

A bitumen sample is oxidized at high temperature under well defined conditions and its physical characteristics are measured before and after this artificiai ageing process. The method is defined in France as AFNOR T 66-032 and in the USA by ASTM D 2872 (Rolling Thin-Film Oven Test). 

Crude petroleum is fractionated into around fifty cuts having a very narrow distillation intervals which allows them to be considered as ficticious pure hydrocarbons whose boiling points are equal to the arithmetic average of the initial and final boiling points, = (T, + Ty)/2, the other physical characteristics being average properties measured for each cut. 

The different cuts obtained are collected their initial and final distillation temperatures are recorded along with their weights and specific gravities. Other physical characteristics are measured for the light fractions octane number, vapor pressure, molecular weight, PONA, weight per cent sulfur, etc., and, for the heavy fractions, the aniline point, specific gravity, viscosity, sulfur content, and asphaltene content, etc. 

The internal kiln surface can contain up to six empty defect zones or zones with thermal physical characteristics different from those of material layers. The initial data are taken from a text file, prepared by any editor in the format MS-DOS. The obtained values of temperatures are written into an output file in the format MS-DOS for subsequent processing with visualization programs. 

The HLB system has made it possible to organize a great deal of rather messy information and to plan fairly efficient systematic approaches to the optimiza-tion of emulsion preparation. If pursued too far, however, the system tends to lose itself in complexities [74]. It is not surprising that HLB numbers are not really additive their effective value depends on what particular oil phase is involved and the emulsion depends on volume fraction. Finally, the host of physical characteristics needed to describe an emulsion cannot be encapsulated by a single HLB number (note Ref. 75). 

A substance is likely to be most soluble in a solvent to which it is most closely related in chemical and physical characteristics. 

Hamer s book in this series (1). which reviewed the synthesis of sensitizing dyes, their physical characteristics, and general photographic properties up to 1958, remains the basic encyclopedic source for the study of methine dyes. 

It appears now that, whatever its usefulness, the resonance theory is somewhat inadequate in explaining and predicting either chemical or physical characteristics of dyes compared to more or less sophisticated molecular orbital calculations. 

The physical characteristics of current commercial mbber and spandex fibers are summarized ia Table 1. Typical stress—straia curves for elastomeric fibers, hard fibers, and hard fibers with mechanical stretch properties ate compared ia Eigute 1. 

Detecting the presence of small, even invisible, amounts of blood is routine. Physical characteristics of dried stains give minimal information, however, as dried blood can take on many hues. Many of the chemical tests for the presence of blood rely on the catalytic peroxidase activity of heme (56,57). Minute quantities of blood catalyze oxidation reactions between colorless materials, eg, phenolphthalein, luco malachite green, luminol, etc, to colored or luminescent ones. The oxidant is typically hydrogen peroxide or sodium perborate (see Automated instrumentation,hematology). 

Particle Size Reduction. Changes in the physical characteristics of a biomass feedstock often are requited before it can be used as a fuel. Particle size reduction (qv) is performed to prepare the material for direct fuel use, for fabrication into fuel pellets, or for a conversion process. Particle size of the biomass also is reduced to reduce its storage volume, to transport the material as a slurry or pneumatically, or to faciHtate separation of the components. 

Several companies offer oils for heat-transfer service. Physical characteristics are summarized in Table 1. The oils discussed herein are widely used. Product brochures on the fluids are available from the manufacturers (3—12). 

The manufacturers of synthetic fluids offer technical service and consultation, and fluid reprocessing service can be arranged between the suppHer and the user. Complete physical properties and detailed information concerning synthetic fluids are reported in the manufacturers product Hterature (13—36). The physical characteristics of the synthetic fluids can be found in Table 1. 

Puilding lime may be quick or hydrated lime, but usually coimotes the latter, where the physical characteristics make it suitable for ordinary or special stmctural purposes (see Building materials, survey). 

Physical characteristics of metals have a significant impact on machinabihty. These include microstmctural features such as grain size, mechanical properties such as tensile properties, and physical properties such as thermal conductivity. 

The treatments used to recover nickel from its sulfide and lateritic ores differ considerably because of the differing physical characteristics of the two ore types. The sulfide ores, in which the nickel, iron, and copper occur in a physical mixture as distinct minerals, are amenable to initial concentration by mechanical methods, eg, flotation (qv) and magnetic separation (see SEPARATION,MAGNETIC). The lateritic ores are not susceptible to these physical processes of beneficiation, and chemical means must be used to extract the nickel. The nickel concentration processes that have been developed are not as effective for the lateritic ores as for the sulfide ores (see also Metallurgy, extractive Minerals recovery and processing). 

In the days of alchemy and the phlogiston theory, no system of nomenclature that would be considered logical ia the 1990s was possible. Names were not based on composition, but on historical association, eg, Glauber s salt for sodium sulfate decahydrate and Epsom salt for magnesium sulfate physical characteristics, eg, spirit of wiae for ethanol, oil of vitriol for sulfuric acid, butter of antimony for antimony trichloride, Hver of sulfur for potassium sulfide, and cream of tartar for potassium hydrogen tartrate or physiological behavior, eg, caustic soda for sodium hydroxide. Some of these common or trivial names persist, especially ia the nonchemical Hterature. Such names were a necessity at the time they were iatroduced because the concept of molecular stmcture had not been developed, and even elemental composition was incomplete or iadeterminate for many substances. 

Fats and fatty oils). For the most part, oil is contained in the kernel or embryo of the seed, though it can also occur in the flesh of the ginkgo fmit and in the endosperm of coconut, palm, and pine nuts. Relative amounts of some fatty acids present in a few types of nuts are given in Table 5. Considerable variations in the percentages of fatty acids have also been reported in both pecan and peanut oils from a variety of sources. (Table 6). (For main physical characteristics and the composition of nut oils, see Fats and fatty oils. 

Olig omerization and Polymerization. Siace an aHyl radical is stable, linear a-olefins are not readily polymerized by free-radical processes such as those employed ia the polymerization of styrene. However, ia the presence of Ziegler-Natta catalysts, these a-olefins can be smoothly converted to copolymers of various descriptions. Addition of higher olefins during polymerization of ethylene is commonly practiced to yield finished polymers with improved physical characteristics. 

The value of pigments results from their physical—optical properties. These ate primarily deterrniaed by the pigments physical characteristics (crystal stmcture, particle size and distribution, particle shape, agglomeration, etc) and chemical properties (chemical composition, purity, stabiUty, etc). The two most important physical—optical assets of pigments are the abiUty to color the environment in which they ate dispersed and to make it opaque. 

Whereas the hydrolysate, TiOg does not have any pigmentary properties, its physical characteristics such as particle size eventually affect its value as... 

Dyes, on the other hand, ate colored substances which ate soluble or go into solution during the appHcation process and impart color by selective absorption of light. In contrast to dyes, whose coloristic properties ate almost exclusively defined by their chemical stmcture, the properties of pigments also depend on the physical characteristics of its particles. 

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