Air content and characteristics

The characteristics and quantity of cement used in the production of air-entrained concrete can have a pronounced effect on the air content and/or... 

As shown in Fig. 8, the airflow vs. bowl capacity for two types of dryers from the same vendor approach linearity as the size of the dryer increases. A similar result is observed for the ratio of the heating vs. bowl capacity for the same dryers, as shown in Fig. 9. Therefore, for a product with constant composition (moisture content) and characteristics (particle size distribution), the time required to dry two different size batches to the same resultant moisture content should be the same if the same inlet temperature was used, and machines with equivalent air flow and heating vs. bowl capacity were used. However, at small scale, differences in the airflow and heating vs. bowl capacity parameters... 

The side-chain chlorine contents of benzyl chloride, benzal chloride, and benzotrichlorides are determined by hydrolysis with methanolic sodium hydroxide followed by titration with silver nitrate. Total chlorine determination, including ring chlorine, is made by standard combustion methods (55). Several procedures for the gas chromatographic analysis of chlorotoluene mixtures have been described (56,57). Proton and nuclear magnetic resonance shifts, characteristic iafrared absorption bands, and principal mass spectral peaks have been summarized including sources of reference spectra (58). Procedures for measuring trace benzyl chloride ia air (59) and ia water (60) have been described. 

Free phenol is a major concern in the manufacture of novolac resins. This is true for several reasons. The strongest drivers are probably EPA classification of phenol as a Hazardous Air Pollutant and worker safety concerns. However, free phenol also has significant technical effects on such parameters as melt flow characteristics. In this role, free phenol may undermine the desired effects of a molecular weight design by increasing flow beyond the desired point. Since free phenol is often variable, the effects on flow may also cause variation in product performance from batch to batch. Fig. 18 shows the effects of free phenol on the flow across a series of molecular weights. Free phenol contents between 1 and 10% are commonly seen. In recent years, much work has been aimed at reducing the free phenol. 

In the mid-latitude region depicted in Fig. 7-5, the motion is characterized by large-scale eddy transport." Here the "eddies" are recognizable as ordinary high- and low-pressure weather systems, typically about 10 km in horizontal dimension. These eddies actually mix air from the polar regions with air from nearer the equator. At times, air parcels with different water content, different chemical composition and different thermodynamic characteristics are brought into contact. When cold dry air is mixed with warm moist air, clouds and precipitation occur. A frontal system is said to exist. Two such frontal systems are depicted in Fig. 7-5 (heavy lines in the midwest and southeast). 

Biomass has some advantageous chemical properties for use in current energy conversion systems. Compared to other carbon-based fuels, it has low ash content and high reactivity. Biomass combustion is a series of chemical reactions by which carbon is oxidized to carbon dioxide, and hydrogen is oxidized to water. Oxygen deficiency leads to incomplete combustion and the formation of many products of incomplete combustion. Excess air cools the system. The air requirements depend on the chemical and physical characteristics of the fuel. The combustion of the biomass relates to the fuel bum rate, the combustion products, the required excess air for complete combustion, and the fire temperatures. 

The initial plastic state of the fresh concrete subsequent to the mixing process, where properties such as the air content, density and workability are normally measured by relevant standard tests, and utilized as a means of control of production. The magnitude of these properties is affected by the addition of water-reducing admixtures, either intentionally or as a side effect, which could result not only in a change in the characteristics in the plastic state, but could also be reflected in changed properties in the hardened state. 

Damp-proofing admixtures include soaps and fatty acids which react with the cement hydrates to modify workability, bleeding and settlement, air content, compressive strength and durability characteristics. Mix proportions, mix consistency, admixture dosage and poor mixing influence the effects produced by the admixture. In cement-rich mixes void content is often increased, resulting in increased permeability. Since the admixture... 

A characteristic of single sized sands is their comparatively high air void contents which usually exceed 30 percent. Since sulfur s role in SAS mixtures is to fill these air voids without the aid of mechanical densification, both economic and performance considerations would require analysis of the maximum permissible air void content the mixture may possess and still be relatively impermeable to water without sacrificing structural integrity. Figure 4 [15] shows the relationship between air voids content and permeability for both SAS and asphaltic concretes as determined... 

Hays et al. (2005) showed that stubble burning can cause a global change in atmospheric air. A study of the physical and chemical characteristics of substances emitted when burning the straw of rice and wheat has shown that the atmosphere receives particles 100nm-l,000nm in diameter, with the level of C02 content and the... 

Overall thermal recovery can he enhanced by cogeneration and advanced technologies such as fluidised bed combustion with fuel pre-drying (6, 7). Useful heat conversion efficiency as a performance characteristic has been evaluated for small boilers using wood fuels, which adopted a combustion equation based on oxidation of lignin, cellulose and hemicelluloses including the effect of air, moisture content and the charcoal fraction in the ash (8). 

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