Humidity scale function

The calculation of the resistance coefficients can be accomplished in the frame of the Monin-Obukhov similarity theory (Monin and Yaglom, 1971). The genuine flux quantities are the friction velocity u and the scale functions 0 and referring to temperature and humidity. The turbulent momentum flux f, the sensible heat flux the mass flux from evaporation and condensation and the corresponding latent heat flux are... 

Humans are sensitive to moisture and can reliably describe the humidity of the environment using word scales as demonstrated in Fig. 5.12. The subject s humidity judgments appear to be functions of the air s dew point, a measure of absolute humidity, and are relatively unaffected by the ambient temperature. Further, people are also good at perceiving skin moisture, as illustrated in Fig. 5.13, where perceived skin wettedness is seen to correlate well with measured skin wettedness. 

Fig. 9-8 Histogram of dissolved solids of samples from the Orinoco and Amazon River basins and corresponding denudation rates for morpho-tectonic regions in the humid tropics of South America (Stal-lard, 1985). The approximate denudation scale is calculated as the product of dissolved solids concentrations, mean armual runoff (1 m/yr), and a correction factor to account for large ratios of suspended load in rivers that drain mountain belts and for the greater than average annual precipitation in the lowlands close to the equator. The correction factor was treated as a linear function of dissolved solids and ranged from 2 for the most dilute rivers (dissolved solids less than lOmg/L) to 4 for the most concentrated rivers (dissolved solids more than 1000 mg/L). Bedrock density is assumed to be 2.65 g/cm. (Reproduced with permission from R. F. Stallard (1988). Weathering and erosion in the humid tropics. In A. Lerman and M. Meybeck, Physical and Chemical Weathering in Geochemical Cycles," pp. 225-246, Kluwer Academic Publishers, Dordrecht, The Netherlands.)...

Dust (especially from industrial activities) and salt spray will also exacerbate atmospheric corrosion (Section 16.4). In enclosed industrial premises, atmospheric corrosion could be minimized by preventing noxious emissions, filtering the air to remove particulate matter, and scrubbing the air with water to remove SO2 and other objectionable gases, although the humidity should itself be kept as low as possible (e.g., steam leaks should not be tolerated). On the global scale, however, the cost to the public of atmospheric corrosion could be substantially reduced by sharply limiting SO2 and, to a lesser extent, NO. emissions from power plants, smelters, automobiles, and other industrial functions. This is an aspect of the acid rain threat (Chapter 8) that is usually overlooked. 

Dry, scaly skin is characterized by a decrease in the water retention capacity of the stratum corneum (SC),1 with water content diminished to less than 10%. Barrier function of the SC is usually declined, and transepidermal water loss (TEWL) is increased because of an abnormality on barrier homeostasis.2 People feel tightness of their skin, and the skin surface becomes rough, scaly, and sensitive. Hyperkeratosis, abnormal scaling, and epidermal hyperplasia are usually observed in the dry skin.2 Keratinization also shows abnormal features.2 These phenomena are commonly observed in atopic dermatitis and psoriasis.3 Dermatitis induced by environmental factors such as exposure to chemicals, low humidity, and UV radiation also shows these features. Thus, many researchers have been investigating the cause and treatment of dry skin, and there is currently great interest in adequate model systems for dry skin studies. In this chapter, I will describe several model systems of dry skin for clinical research of dermatitis associated with skin surface dryness and also mention recent studies to improve the dry skin. 

If a functional coat is to be evaluated, the scale-up requires that critical process parameters that affect coating uniformity be evaluated. Coating conditions such as atomization, gun location, and bed movement become critical processes. The curing rate of the film must be evaluated. Drying conditions (temperature and humidity) and drying time must be defined and ranges validated. 

The general problems of forecasting materials damage from both air pollution and acid precipitation have been considered before in previous papers (1-2). This previous work focussed on zinc as a paradigm for all materials at risk, and considered uncertainties in damage functions, variability in atmospheric conditions over space and time, and the general problem of inventorying the materials at risk. An Important topic in these previous papers was whether the interaction between SO2 ambient concentrations and relative humidity (RH) would require the consideration of time scales... 

The significance of this model is that it describes the optimal situation for water permeation into the spore and therefore ethylene oxide permeation to its target site as a function of the moisture content of the spore and the relative humidity of the environment during exposure. The rate of microbial inactivation therefore increases (as long as all other factors are held constant) with increased relative humidity during exposure. Kaye and Phillips [4] demonstrated a 33% RH optimum for microbial inactivation as a result of exposure to ethylene oxide. In practical situations it is better to err on the side of too much rather than too little moisture. With industrial-scale ethylene oxide sterilization, humidity levels are usually in the range of 50% to 60% RH. The upper limit is usually dictated by deleterious effects on packaging. 

To determine the drying rate, the mass of a sample placed in the airflow (constant temperature, humidity, and velocity) must be measured as a function of time. In order to obtain results that can be applied for scale-up, the following aspects must be taken into account the sample must not be too small and the conditions of drying must if possible be identical to the conditions anticipated in the industrial unit [1,17] ... 

Milota (2001) compared the emissions from various North American lumber species in a small-scale kiln with those from the same wood in a commercial kiln. The laboratory kiln functioned like the mill kiln with respect to venting characteristics, temperature, and humidity, but it dried the wood faster, possibly because the load is... 

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