Hugh C. Wood

Modeling of Vegetation Permittivity at Microwave Frequencies

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 degC and at an MC ranging from 12% to 73% in wet basis

SIMULATION OF THERMAL AND DISINFESTATION CHARACTERISTICS OF A FORAGE DRYER

ABSTRACT The thermal morality data for the cocoon stage of the insect Sitodiplosis mosellana (Gehin) were fitted to a normal distribution function and a probit viability equation was developed. The equation was included in a new tunnel dryer simulation program to compute the cumulative mortality of the insect during baled- forage drying. From the analysis it became clear that the temperature of dried forage remained at or above 60 C during drying and thus 99.99% kill of the insect was assured.

Prediction of moisture content of alfalfa using density-independent functions of microwave dielectric properties

The use of density-independent functions of the dielectric properties of chopped alfalfa, calculated from microwave reflection coefficients from 300 MHz to 18 GHz, was studied for determining moisture content in the range from 12% to 73%, wet basis, at bulk densities from 0.139 to 0.716 g cm−3 at 20 °C. Prediction of moisture content with worst-case relative errors of about 3% or less over the range from 20% to 73% confirmed promising prospects for use of such density-independent functions for reliable moisture measurement for important plant materials.

Thermal kill of wheat midge and Hessian fly

Abstract Heat treatment effects on the survival rate of the wheat midge (Sitodiplosis mosellana [Gehin]) and Hessian fly (Mayetipla destructor [Say]) were studied by exposure of wheat midge larval cocoons to 90, 80, 70, 60, 55, 52.5, 50, and 47.5°C temperatures in a convection oven. Cocoons did not survive temperatures 55°C and higher when exposed for 3 min. Wheat midge larvae were killed at 52.5°C in about 7 min. At 47.5°C, some larvae survived for 26 min but were dead when the exposure time was extended to 37 min. Comparison of mortality of wheat midge larvae and Hessian fly showed no difference in response to 50 to 90°C. Effects of heat treatment on the two species were similar suggesting thermal treatment of the wheat midge could be applicable to the Hessian fly.

Fuzzy-logic-based plasma-position controller for STOR-M

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.

HEAT TREATMENT OF CHOPPED ALFALFA IN ROTARY DRUM DRYERS

ABSTRACT This paper deals with the heat treatment of alfalfa chops during the high temperature dehydration process. It outlines the dryer characteristics, difficulties and potential errors in measuring temperatures in the dryer, computation techniques, the relationships between moisture and temperature during drying, and the potential effect of dehydration on the destruction of the insect Hessian Fly due to elevated temperatures. From the analysis based on an existing computer model for dehydration of alfalfa chops, and the available field data, it is shown that the dried chops will attain a temperature of 90°C or higher when the input temperatures are between 500°C and 800°C. These conditions apply to the drying of wet alfalfa (moisture content more than 55 percent wet basis). The plant material loses a large portion of its moisture in the first few seconds in the dryer. The rapid release of moisture may cause the rupture or detachment of particles such as eggs, larva, pupa, and insects from the plant ma...

Microwave Dielectric Properties of Alfalfa Leaves From 0.3 to 18 GHz

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°C and 30°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°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°C, the measured permittivity followed a trend similar to that of free saline water and was characterized by the Debye equation. Below 0°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.

A neural network approach to analysing multi-component mixtures

This paper describes an approach for determining the individual analyte concentrations in a mixture of analytes using sensor fusion. Sensor fusion here is considered to be a process of gathering information from many different sources and combining these data to acquire pertinent information. The research reported in this paper uses sensor fusion and simulated, partially selective sensors. Through the use of simulated sensors, this research has investigated the advantages and limitation of sensor fusion and artificial neural networks. A three-layer back-propagation network was trained on a subset of component space and it was tested for its ability to generalize, where component space is defined as all possible combinations of input analyte concentration. A learning rate of 0.1 was used and no momentum terms were used. This research has shown that sensor fusion with an artificial neural network can accurately map sensor outputs to the actual input analyte concentrations. This research has also shown that increasing the number of sensors used improves the neural network performance. The neural network approach was found to be, under most circumstances, as good as or better than a mathematical technique using a curve fitting method of addressing the problem. The neural network technique was also found to be significantly faster than the mathematical technique and to possess good noise rejection attributes.

Microprocessor-based controller for plasma position in a tokamak

A high-speed microprocessor-based controller and its application to the plasma position in the STOR-M (Saskatchewan torus-medium) tokamak is described. An adaptive control procedure based on a high-speed digital signal processor has been used to improve the controller performance. The fundamental functions of this system are the plasma dynamics modeling, the controller adjustment based on parameter optimization, and real-time feedback control. The performance of this high-speed digital controller is described, and a simulation study is discussed. Plasma position measurement using magnetic probes is described. >

A controller for plasma motion in a Tokamak based on model estimation

A simple model and its application in designing the plasma position control system in the Saskatoon Torus Medium (STOR-M ) Tokamak are described. Estimating the model parameters, the design of a controller, plasma position measurement, the design of a power driver, and the implementation and testing of the complete system are included. The following assumptions are made to simplify the plasma position model: the plasma is treated as a moving axisymmetric, current-carrying filament; the iron-core of the transformer is approximated by an infinitely long cylinder; and the STOR-M vacuum vessel is constructed of type-304L stainless steel, is circular in cross-section, and is 4 mm in thickness. The model was very useful in the early stages of the design, but due to practical constraints the parameters of the model could not be determined very accurately. A least-squares-error algorithm was used offline to determine revised estimates of the models parameters. Based on these values, the PID (proportional-integral-derivative) controller was tuned. A 30 kA plasma has been successfully contained for a time of 50 ms, which is the maximum time required for this machine. >