Effect Of Temperature Range Research Articles

Studies on the Thermal Degradation of Poly(styrene-butadiene)

Poly(styrene-butadiene) (PSB) is pyrolyzed under an inert atmosphere in different temperature ranges by using differential thermal analysis (DTA) and pyrolysis?gas chromatography (Py-GC). Fourier transform infrared spectrometry (FTIR) is used for investigating the pyrolysis residue. The pyrolyzed gaseous products are analyzed by gas chromatography (GC). The main products are styrene, C2 hydrocarbons, and vinylhydrohexane. The effect of temperature range on the relative yields of the major decomposition products is studied. Based on these data, the thermal degradation mechanism of PSB is also proposed. It is believed that the pyrolysis process and its products cause no environmental impact.

Rapid freezing injury in red spruce: seasonal changes in sensitivity and effects of temperature range.

On calm, cold days in winter, sun-exposed needles of red spruce (Picea rubens Sarg.) may warm 10 to 20 degrees C above ambient air temperature, and undergo rapid (>/= 1 degrees C min(-1)) fluctuations in temperature as light breezes or passing clouds alter the energy balance of the foliage. It has been proposed that the resulting rapid freeze-thaw cycles (freezing stress) cause a type of winter injury in montane red spruce that is characterized by necrosis of sun-exposed foliage. In autumn and winter, we monitored rapid freezing stress response of needle sections from 10 montane red spruce trees by subjecting needles to rapid freezing over the temperature span typically recorded in the field. In autumn, experimental rapid freezing stress produced severe injury only at temperatures considerably lower than expected for that time of year. In winter, rapid freezing caused occasional, moderate injury in fully hardened foliage of trees susceptible to both slow and rapid freezing. Seasonal changes in sensitivity to rapid and slow freezing were correlated, suggesting that environmental factors that are known to affect sensitivity to slow freezing may also affect sensitivity to rapid freezing. Experimental manipulation of the start and end temperatures of rapid freezing stress events showed that moderate to severe needle injury can occur in susceptible trees at temperature spans slightly more extreme than those typically recorded in the field. The extent of injury was similar at different starting temperatures if rapid freezing occurred over the same temperature span. Year-old foliage was consistently less sensitive to rapid freezing stress than current-year foliage, but some year-old foliage was damaged when the rapid freezing stress regime caused severe injury in current-year foliage. We conclude that rapid freeze-thaw cycles can explain light to moderate injury of current-year foliage, but they do not explain the more severe and widespread pattern of foliar damage that has occurred intermittently over at least the last 18 years.

Thermal fatigue of Ti-24Ai-11NB/SCS-6

The effect of thermally cycling in air with no applied load was studied using the Ti-24A1-11Nb (atomic percent)/SCS-6 composite system. Mechanisms of damage determination were observable cracking and residual tensile properties. Either the number of cycles or the temperature range was varied from specimen to specimen. Effects of number of cycles were investigated using a temperature range of 150 °C to 815 °C. Comparisons of temperature range effects were made at a constant cycle count of 500. Matrix cracking was observed at a †T of 450 °C and greater when oxidation was significant. Transverse cracking was not observed in specimens that were cycled to maximum temperatures where oxidation was insignificant, even for †T's as large as 500 °C. A decrease in tensile properties coincided with the observed transverse matrix cracking.

STUDY OF THE THERMAL PROPERTIES FOR SINGLE CRYSTAL OF POLYBIS-(p-TOLUENE SULFONATE) OF 2,4-HEXADIYNE-1, 6-DIOL(PTS)

The thermal properties for PTS are studied by photoacoustic effect in temperature range 175-225 K. It is found that there is a peak of C3K at 200 K (here C3 and K are the specific heat and thermal conductivity of PTS, respectively), which shows crearly the existence of a second order phase transition in view of thermal propertis for the first lime. An anomalous thermal conductivity in the above temperature range is deduced from experiment results.

Effect of temperature range on extent of microstructural degradation during thermal cycling of unidirectionally solidified eutectic composite

Abstract A refractory carbide strengthened nickel-base alloy was directionally solidified at 5 mm h—1 to produce a regular well-aligned eutectic alloy consisting of niobium carbide fibres in a nickel–chromium matrix. The fibrous microstructure which is extremely stable under isothermal annealing conditions suffers severe degradation during thermal cycling. The upper cycling temperature and the temperature range of the cycling treatment were found to strongly affect the extent of fibre degradation, which increased as both upper cycling temperature and temperature range increased. Fibre degradation occurred by nucleation and growth of nodules at the corners of some fibres and by the dissolution of other fibres. Possible mechanisms for such microstructural breakdown are discussed.

熱疲労試験における高周波加熱コイルの形状と試験片の温度分布

On the high frequency heating apparatus used for thermal fatigue tests, the relation between the shape of heating coils and the temperature distribution of specimens was experimentally examined for SUS 304 stainless steel. This report describes the relation between heating coil dimensions and heating rate, the most ideal coil shape for various specimen types, and the effects of temperature range and specimen shape on temperature distribution.The results obtained are as follows:(1) The heating rate increases with decreasing distance from specimen surface to heating coil and with increasing coil tube diameter.(2) For the general cylindrical and hour glass type specimens, the most ideal coil shapes are a separate type and a parallel type coil, respectively, as judged from the point of temperature distribution.

Response of corn (zea mays l.) in the pre-tassel initiation period to temperature and photoperiod

Controlled-environment facilities were used to examine the effects of temperature and photoperiod on tassel-initiation time, leaf number and rate of leaf initiation of two corn hybrids. The effect of diurnal temperature range on tassel-initiation time and leaf number was also investigated. There was a consistent decrease in time to tassel initiation as temperature was increased from 15° to 25°C regardless of photoperiod. There was no difference in tassel initiation time at 25° and 30°C under all photoperiods for both hybrids. Photoperiod increased the time to tassel initiation at all temperatures, however, the change in time was more pronounced at low temperature (15°C). Temperatures of 15, 20 and 25°C had little effect on changing the number of leaves. However, the 30°C-treatment resulted in an appreciable increase in leaf number over that of other temperature treatments. As photoperiod was extended, leaf number increased at all temperatures for both hybrids. Average leaf number increased by 2.1 for each hybrid by lengthening photoperiod from 10 to 20 h. The rate of leaf initiation was nearly doubled for United 108 and more than doubled for Guelph GX 122 when temperature was increased from 15° to 30°C. The two hybrids exhibited a pronounced difference in leaf-initiation rate at high temperature (30°C). There was a small change in the rate of leaf initialtion with photoperiod. It is concluded that the increase in leaf number with increasing photoperiod resulted from the prolongation of the time to tassel initiation. At low mean temperature (15°C), there was an appreciable delay in tassel-initiation time as the diurnal range was increased from 0.0 to 17.2°C. The delay at these ranges became smaller at the 20°C-mean temperature. At 25°C-mean temperature, there was a pronounced delay with an increase of range from 8.6 to 17.2°C. The number of leaves increased with mean temperature and diurnal range. However, the effect of temperature range became less pronounced at high mean temperature.