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Microwave Systems (microwave + system)

Distribution by Scientific Domains

Chemistry	50%
Polymers and Materials Science	33%

Selected Abstracts

Aseptic Processing of Sweetpotato Purees Using a Continuous Flow Microwave System

JOURNAL OF FOOD SCIENCE, Issue 9 2005
Pablo Coronel
ABSTRACT: Sweetpotato purees (SPP) were aseptically processed using a continuous flow microwave system to obtain a shelf-stable product. The dielectric properties of SPP were measured, and the dielectric constant and loss factor were within the range of the published values for fruits and vegetables. Small-scale tests were conducted in a 5-kW microwave unit to determine changes in color and viscosity with different thermal treatments. The results of these tests showed that color values (L*, a*) and viscosity did not change significantly compared with the untreated control. Pilot-scale tests were then conducted in a 60-kW microwave unit where the product was heated to 135 °C and held at that temperature for 30 s. The pilot-scale test produced a shelf-stable product with no detectable microbial count during a 90-d storage period at room temperature. This is the 1st report of aseptically packaged vegetable puree processed by a continuous flow microwave heating system. [source]

Textured Microstructure and Dielectric Properties Relationship of BaNd2Ti5O14 Thick Films Prepared by Electrophoretic Deposition

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2009
Zhi Fu
Abstract An alternative approach to tailor the temperature coefficient of permittivity (TC,r) of high Q dielectric BaO,Re2O3,TiO2 (Re: rare earth elements) thick films is presented. 10- to 80-µm-thick BaNd2Ti5O14 (BNT) films are fabricated by electrophoretic deposition on Pt foils under different processing conditions. Observed anisotropic grain growth is facilitated by constrained sintering. The increase of the sintering temperature increases markedly the aspect ratio of the grains, decreases the dielectric permittivity and TC,r changes from ,114 to +12,ppm °C,1. By controlling the sintering temperature, near-zero TC,r, high Q thick films can be fabricated with 45,<,,r,<,70. These findings are of technological relevance since they demonstrate that control of substrate constraint and sintering conditions can be used to control grain anisotropy and thus microwave properties of the BaO,Re2O3,TiO2. The thick films facilitate scaling to small device sizes for high frequency operation. Similar observations are expected in other microwave systems thus opening further technological opportunities. [source]

Rain rate conversion for various integration time for equatorial and tropical climates

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 4 2008
J. S. Mandeep
Abstract Rain rate statistics are derived on the basis of rain gauge recordings having effective integration times of 5,min or more. The conversion of such data to equivalent statistics for an effective integration time of 1,min is important to the design of both terrestrial and earth-space microwave systems. Tipping bucket precipitation records for seven locations in South East Asia countries have been analysed and present the results of a testing activity performed on four conversion methods of rain rate integration time, from 5, 10, 30 and 60 to 1,min. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Microwave-Assisted Polymer Synthesis: State-of-the-Art and Future Perspectives

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2004
Frank Wiesbrock
Abstract Summary: Monomodal microwaves have overcome the safety uncertainties associated with the precedent domestic microwave ovens. After fast acceptance in inorganic and organic syntheses, polymer chemists have also recently discovered this new kind of microwave reactor. An almost exponential increase of the number of publications in this field reflects the steadily growing interest in the use of microwave irradiation for polymerizations. This review introduces the microwave systems and their applications in polymer syntheses, covering step-growth and ring-opening, as well as radical polymerization processes, in order to summarize the hitherto realized polymerizations. Special attention is paid to the differences between microwave-assisted and conventional heating as well as the "microwave effects". Results of search on number of publications on microwave-assisted polymerizations, sorted by year. [source]

Determination of total urinary mercury by on-line sample microwave digestion followed by flow injection cold vapour inductively coupled plasma mass spectrometry or atomic absorption spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2002
M. Bettinelli
The total mercury content in urine was determined by inductively coupled plasma mass spectrometry with the so-called cold vapour method after on-line oxidative treatment of the sample in a microwave oven (FI-MW-CV-ICPMS). Use of a KBr/KBrO3 mixture, microwave digestion, and the final oxidation with KMnO4, assure the complete recovery of the organic forms of Hg which would be difficult to determine otherwise if using only the CV-ICPMS apparatus. Quantitative recoveries were obtained for phenyl Hg chloride (PMC), dimethyl Hg (DMM), Hg acetate (MA) and methyl Hg chloride (MMC). Use of automatic flow injection microwave systems (FI-MW) for sample treatment reduces environmental contamination and allows detection limits suitable for the determination of reference values. Since no certified reference materials were commercially available in the concentration ranges of interest, the accuracy of the proposed procedure has been assessed by analysing a series of urine samples with two independent techniques, ICP-MS and AAS. When using the FI-MW-CV-ICP-MS technique, the detection limit was assessed at 0.03µg/L Hg, while with FI-MW-CV-AAS it was 0.2µg/L Hg. The precision of the method was less than 2,3% for FI-MW-CV-ICP-MS and about 3,5% for FI-MV-CV-AAS at concentrations below 1µg/L Hg. These results show that ICP-MS can be considered as a "reference technique" for the determination of total urinary Hg at very low concentrations, such as are present in non-exposed subjects. Copyright © 2002 John Wiley & Sons, Ltd. [source]