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Moisture content of a commercially important forage biomass such as alfalfa (Madicago sativa), the specific alfalfa that we used in this research, is essential at various stages of production including harvesting, baling, storing, pelleting, and cubing. The moisture content of commodities such as green tea leaves also plays a key role in retaining natural taste and color during drying. The dielectric constants and the dielectric loss factors of chopped alfalfa were measured with moisture contents between 11.5% and 73%, wet basis (wb), and bulk densities ranging over 139 kg?m-3 to 716 kg? m-3. They were measured at 10 frequencies between 1 and 18 GHz at 20 °C with an open ended coaxial probe with 20 inputs for artificial neural networks. A three-layer neural network with 20 inputs, five hidden nodes, and one output for moisture content was built on an error back-propagation algorithm with momentum and adaptive learning techniques to predict the moisture content of alfalfa. It was independent of bulk density with a root-mean-square error of 1.09%. The prediction of moisture content of alfalfa independent of bulk density in 12 seconds exhibited the potential of this technique in measuring the moisture content of alfalfa and other medicinal and cash crops in batch and in production moisture measurements. [ABSTRACT FROM PUBLISHER]

Dielectric properties (i.e., permittivity) are essential in designing, simulating, and modeling microwave applications. The permittivity of stacked leaves of alfalfa (Medicago sativa ) were measured with a network analyzer and a coaxial probe, and the effect of moisture content (MC: 12%–73% wet basis), frequency (300 MHz to 18 GHz), bound water (Cole–Cole dispersion equation), temperature (-15\ ^\circ\C and 30 ^\circ\C), leaf-orientation, and pressure (0–11 kPa) were investigated. The measured permittivity increased with MC. A critical moisture level (CML) of 23% was reported, below which the permittivity decreased with increasing frequency at 22 ^\circ\C. Above CML and up to 5 GHz, the dielectric constants followed the Cole–Cole dispersion, and the dielectric loss factors consisted of ionic and bound water losses. Above 5 GHz, the behavior of the dielectric constant was similar to that of free water, and the polar losses became dominant. Above 0 ^\circ\C, the measured permittivity followed a trend similar to that of free saline water and was characterized by the Debye equation. Below 0 ^\circ\C, it was dominated by nonfreezing bound and unfrozen supercooled moistures. The relaxation parameters and the optimum pressure (9 kPa) for the leaf measurements were determined. The effects of variations among the samples, and their orientations had negligible effects on the measured permittivity. [ABSTRACT FROM PUBLISHER]

When materials are to be treated with microwaves for different purposes such as drying, online moisture measurements, disinfestation, and remote sensing, thorough knowledge of the material dielectric properties becomes extremely important. Unlike for other materials, measurement of vegetation dielectric properties is very complicated due to the nature of the materials themselves. Hence, vegetation dielectric models that require fewer accurately and easily measurable physical quantities are of great importance. Therefore, dielectric models that only require the measurement of moisture content (MC) have been investigated for alfalfa, a plant material that has high commercial value in national and international markets. The models were developed by measuring the dielectric properties by using an open-ended coaxial probe at frequencies ranging from over 300 MHz to 18 GHz at 22 °C and at an MC ranging from 12% to 73% in wet basis. [ABSTRACT FROM AUTHOR]

The successful operation of a tokamak fusion reactor rests on its ability to stably confine a very hot plasma. The quality of the discharge in the Saskatchewan TORus-Modified (STOR-M) tokamak is strongly related to the position of the plasma column within the discharge vessel. If the plasma column approaches too near the wall, then either minor or complete disruption occurs. Consequently it is necessary to be able to control dynamically the position of the plasma column throughout the entire discharge. A fuzzy-logic-based controller was designed and implemented for this purpose. This controller was evaluated on the STOR-M tokamak during actual operation, and was found to provide reliably a high quality of control. The actual performance of the fuzzy-logic-based controller at actually controlling the position of the plasma column within the STOR-M tokamak is evaluated against the actual performance of a proportional-integral-derivative (PID) controller. [ABSTRACT FROM AUTHOR]