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Operational Temperature (operational + temperature)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

Temperature dependency of granule characteristics and kinetic behavior in UASB reactors

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2004
Hsin-Hsien Chou
Abstract When an inhibitory substrate, phenol, was treated under mesophilic conditions (25, 30, 35, and 40 °C), the upflow anaerobic sludge bed (UASB) reactors at 30 °C resulted in the greatest amount of biomass and the largest granule size, while the UASB reactors at 25 °C resulted in the smallest granule size and the greatest amount of wash-out of sludge. The granule size tended to be negatively correlated with the amount of wash-out of sludge. With an increase in temperature, the kinetic constant k for anaerobic phenol degradation increased and the half saturation constant (Ks) decreased. The mass fraction of methanogens (f) increased with increasing operational temperature in the UASB reactors and the activation energy (Ea) for acetate methanogenesis was larger than that for phenol acidogenesis in the batch reactors, indicating that the operational temperature imposes a more influential effect on methanogens than on acidogens. From the results of the activity of acidogens and methanogens (expressed in specific COD utilization rate), the rate-limiting step is phenol acidogenesis. Copyright © 2004 Society of Chemical Industry [source]

Studies on Chromatographic Properties of Perhydroxycucurbit[6]uril as a New Type of Gas Chromatographic Column Packing Material

CHINESE JOURNAL OF CHEMISTRY, Issue 2 2008
Lai-Sheng LI
Abstract Perhydroxycucurbit[6]uril {(HO)12CB[6]} has been used successfully as a stationary phase for packed column gas chromatography for the first time. Perhydroxycucurbit[6]uril stationary phase (PSP) exhibited wide operational temperature, outstanding thermostability and good selectivities to various organic compounds, such as alkanes, aromatic hydrocarbons, alcohols, esters, ketones, amines, etc. It was also found that some positional isomers, such as disubstituted benzenes could be well separated on this column. PSP has excel1ent separation abilities to some complicate samples, for example, commercial toilet water. Some mechanism of the new packing for GC-separation was preliminarily discussed. It was observed that the partial inclusion complexation of PSP with analytes could improve separation selectivity and column efficiency, instead of complete inclusion. Moreover, PSP exhibited low baseline shift even at dramatically programmed temperature for complicate samples covering a wide boiling point range so as to fast assay. [source]

Reliability of capacitive RF MEMS switches at high and low temperatures

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2004
Yong Zhu
Abstract Some applications of RF MEMS switches, such as aircraft condition monitoring and distributed satellite communication, present a unique challenge for device design and reliability. This article examines these switches when operational temperatures in the range ,60°C to 100°C are envisioned. The basic operation of a capacitive MEMS switch is described and two tools for examining device reliability, modeling, and on-chip experimentation, are discussed in the case of capacitive MEMS switches. 1D, 2D, and 3D models are presented with emphasis on 3D coupled-field finite-element analysis, including temperature effects. Results and findings from the 3D simulations are reported. In particular, the advantages of employing corrugated membranes in the design of RF MEMS switches are assessed. Their performance in terms of reliability as a function of temperature is quantified. The effects of corrugation on the geometric parameters are discussed in the context of device-design optimization. In order to assess reliability experimentally, the M-test and the membrane deflection experiment (MDE) are reviewed due to their on-chip characteristic and simplicity. Ways in which these experimental/computational methodologies can be combined for identifying material properties and device performance is also highlighted. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 317,328, 2004. [source]