Detection, thermal temperature measurement

A number of variations of the transient hot-wire method have been devised, and an optical method to detect the temperature rise has been used. A modified transient hot-wire technique using a mercury-incapillary probe was introduced by Nagashima et al., in which a thin mercury thread was used as a heater-thermometer and the capillary wall as an insulator. Using this method, they measured the thermal conductivity in mixture systems such as (Na, K)N03, (Li, Na)N03, and HTS(KN03-NaN03-NaN02, 44-7-49 mol.%). ... 

The performance of the temperature controller was measured in the tracking mode. Figure 6.18 shows a graph, where the temperature of one of the three microhotplates is kept at a constant temperature of 300 °C, the temperature of the second microhotplate is modulated using a sine wave of 10 mHz, while rectangular temperature steps of 150 °C, 200 °C, 250 °C, 300 °C, and 350 °C have been appHed to the third microhotplate. Temperature measurements on one of the hotplate that has been operated at constant temperature in the stabihzation mode showed a variation of less than 1 °C, even though the temperature of the neighboring hotplates was, at the same time, modulated dynamically (sine wave, ramp, steps). This is a consequence of the individual hotplate temperature control, without which thermal crosstalk between the hotplates would have been clearly detectable. The power dissipation of the chip is approximately 190 mW, when all three hotplates are simultaneously heated to 350 °C. In the power-down mode, the power consumption is reduced to 8.5 mW. 

Total Radiation Pyrometers In total radiation pyrometers, the thermal radiation is detected over a large range of wavelengths from the object at high temperature. The detector is normally a thermopile, which is built by connecting several thermocouples in series to increase the temperature measurement range. The pyrometer is calibrated for black bodies, so the indicated temperature Tp should be converted for non-black body temperature. 

Carbon-14 content is measured by specially designed gas proportional counters (7. Aerosol samples are first converted to CO2 by combustion in a macroscale version of the thermal evolution technique. A clam shell oven was used to heat the sample for sequential evolution of organic and elemental carbon under equivalent conditions. Due to the possibility of thermal gradients, conditions in the macroscale apparatus were adjusted to produce the same recoveries of total carbon (yg C per cm of filter area) as for the microscale apparatus. Carbon-14 data are reported as % contemporary carbon based on the 1978 1 C02 content in the atmosphere. Aldehyde data referred to in this paper were obtained by impinger sampling in dinitrophenylhydrazine/acetonitrile solution and analysis of the derivatives by HPLC with UV detection (12). Olefin measurements were made by a specially designed ozone-chemiluminescence apparatus (13) difficulties in calibration accuracy and background drift with temperature limit its use to inferences of relative reactive hydrocarbon levels. 

Outdoor exposure of these hlgh-denslty samples for the last 18 years caused no substantial change due to surface oxidation. Bulk changes similar to those found In low-density polyethylene were also found In these high density materials. The melt Index slowly decreases and the overall thermal stability measured at high temperature by thermal analysis decreases. However, the secondary crystallization seen In low-density polyethylene was not detected In these high density compounds. 

In a first realization, Jahne et al. (1989) forced a periodical heat flux density onto the water surface using a chopped heat source above the water surface. The temperature response at the water surface was detected with point measuring radiometer. In a further implementation of this technique, HauBcckcr (1996) developed the so-called passive controlled flux method that estimates the skin-bulk temperature difference under natural heat flux conditions assuming a surface renewal model. The naturally occurring heat fluxes at the ocean surface (latent, sensible and long wave radiative heat flux) cause the surface temperature to decrease or increase depending on the direction of these fluxes. The net heat flux forces a skin-bulk temperature difference AT across the thermal sublayer, commonly referred to as the cool skin of the ocean (compare Fig. 2). 

Thermosonimetry (TS) is defined by the ICTA as that technique in which the sound emitted by a substance is measured as a function of temperature whilst the substance is subjected to a controlled temperature programme. As a thermal analysis technique, TS is concerned with the detection and interpretation of the various acoustic emissions occurring prior to, during, and after thermal events (127). It can thus contribute to the elucidation of the thermal behavior of solid materials and to an understanding of the dynamic processes of the solid state. The technique has been developed for thermal analysis measurements principally by Lonvik (128, 143) with other applications described by Clark (127) and Rajeshwar et al. (129). 

A pyrometer is a non-contacting temperature measurement instrument that is usually used for temperatures above 500 °C, although with some modifications it can measure temperatures below room temperature. The word pyrometry comes from the Greek words pyro (Are) and meter (measure). The basic principle relies on the notion that all bodies emit thermal radiation proportional to their temperature. Pyrometers detect this thermal radiation and through Planck s law the temperature can be determined. 

Heat capacity measurements of Polovov (1973) (300-950 K) are shown only in the form of a small graph, but they detect an anomaly at 694 K which may well correspond to the eutectoid in the samarium-samarium hydride system and they also detect a further anomaly at 830 K which may well be the reduced alpha-beta transformation temperature. Heat capacity measurements of Kurichenko et al. (1985) (900-1350 K) are also shown in the form of a small graph, but in particular, their thermal diffusivity measurements show an anomaly at 980 K which may also be associated with the alpha-beta transformation. 

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