Temperature/thermal regime

Water temperature modification is an important consequence of river regulation. We can consider that there are two types of impacts on the thermal regime direct and indirect alterations. The direct alterations are those in which there is a direct modification of the temperature of water, mainly through the release of water at a temperature different from the expectable in natural conditions. The indirect... 

As an example of the alterations produced by this type of reservoirs, we quote the case of the lake Powell in the river Colorado. After the construction of this reservoir, there was a change in the thermal regime, mainly consisting of a decrease of the mean annual temperature by 10-15°C, with water colder in summer and warmer in winter. While before the construction of the reservoir the water temperature along the year fluctuated between 0 and 29.5°C, afterwards it only varied between 6 and 15°C [11, 12]. 

Another example is the Keepit Dam in the river Namoi (Australia). The alterations produced by this dam on water temperature were studied by Preece and Jones [13]. This dam has a storage capacity of 423 hm3, a maximum depth of 40 m and water is released through a fixed-level intake structure with the inlet located at 24 m bellow full supply level. The mean discharge of the river Namoi downstream of the dam is circa 7 m3/s. Just downstream from the dam, a 5°C decrease of the annual maximum temperature was observed, and a delay of the same of 22 days. As the distance increased, the natural thermal regime was recovered at 100 km downstream from the dam, the differences in water temperature with respect to the situation former to the construction of the dam were less than 1°C. 

The management of reservoirs affects the thermal regime of downstream rivers in various - and often antagonistic - ways. To analyze water temperature changes, it is useful to distinguish between (1) the reaches immediately below the reservoir, (2) the abstraction section, and (3) the receiving river below the water release. 

Withdrawal towers in dams allow corrections to the altered thermal regime without much additional effort. Especially in clear water reservoirs, withdrawal towers allow managers to choose water at its natural temperature and to reduce artificial seasonal temperature shifts. Again, retention basins have the same... 

The thermal regime of the reacting mixture between two walls of strongly differing temperature is studied, and the minimum (limiting) amount of evacuated heat found for which ignition at the hot wall still does not occur (a steady regime is possible). 

An important difference between the PS-gas systems (Kwag et al., 1999) and the PDMS-C02 system (Gerhardt et al., 1997) is that the viscosity measurements of the PS-gas systems are conducted at temperatures within 75 °C of T of PS, whereas the PDMS-C02 measurements were performed nearly 200 °C above Tg of PDMS. The difference between these two thermal regimes leads to several differences in the observed rheological behavior. The viscosity reductions relative to the pure polymer are much greater for PS-gas systems than for PDMS-C02 systems at similar dissolved gas compositions, and the dependence of ac on temperature is much more pronounced for the PS-gas systems. These trends are consistent with the observations of Gerhardt et al. (1997, 1998) that the effect of dissolved gas on polymer melt viscosity occurs primarily through a free-volume mechanism. 

The temperature dependence of the observed emission is equally well interpreted in the scheme of Section II.D.3.b The lines emitted from the main distribution D, are asymmetric, with a width of the order of kT for the high-energy part. At very low temperature (0.4 K)86 the main distribution approaches a width of about 4 cm - which indicates that the thermalization regime is slower than the radiative relaxation rate, of the order of 1 ns. In addition, the shape of the second distribution D2, at 25 082 cm1, sharpens as the thermal barrier,85 which inhibits the relaxation very near the middle of the zone, weakens at very low temperature. 

For the reactor inlet temperature to be markedly below 100°C (which avoids the corrosion and plugging problems ), fuel mass fractions equivalent to 25% CH3OH seem to be necessary for the thermal regime of a flame. This value is supported by experiments as well as it is by theory. In a future configuration it can be lowered if the following improvements in comparison to the presented bench-scale reactor are achieved ... 

Ehlers T. A., Armstrong P. A., and Chapman D. S. (2001) Normal fault thermal regimes and the interpretation of low-temperature thermochronometers. Phys. Earth Planet. Inter. 126, 179-194. 

Figure 7 Vertical profiles of formaldehyde, HCHO, in the snowpacks in central Alaska described in Figure 3 and subjected to different thermal regimes a temperature gradient (HGM) regime, and a quasi-isothermal (QIM) regime.

At low temperatures, the small-polaron moves by Bloch-type band motion, while at elevated temperatures it moves by thermally activated hopping mechanism. Holstein (1959), Friedman and Holstein (1963), Friedman (1964) performed the theoretical calculations of small-polaron motion and showed that the temperature dependencies of the small-polaron mobility in the two regimes are different. In the high-temperature hopping regime, the electrical conductivity is thermally activated and it increases with increasing temperature. As shown by Naik and Tien (1978), its temperature dependence is characterized by the following equation... 

The temperature and percent oxygen saturation were associated with the thermal characteristics of sampling sites and were responsible for 14 percent of variance In the SRP water systems. The thermal regime significantly increased the concentration of Mg, Na and ortho-phosphate... 

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