A linear model considering the effect of eddy currents is shown to be useful for the analysis of the dynamics of active magnetic thrust bearings in which electromagnet cores are composed of solid steel. The dynamics of the magnetic control force are modeled by the first-order time-lag system with unknown parameters : gain and time constant. The parameters are estimated from experimental results that indicate the static relation between the coil current and the magnetic control force, and the frequency response of magnetic flux for an input signal to a power amplifier. The effect of eddy currents on the dynamics is confirmed by the frequency characteristlcs of magnetic flux for the coil current. Model simulations with estimated parameters are compared with experimental results, and good agreement is obtained in frequency response in a linear range and in impulse responses with rotor displacements smaller than half the air gap.
Environmental stress can induce changes in physiological and physical conditions of a plant, and these changes influence the dielectric properties of the plant, which can be detected by measuring microwave transmission characteristics (scattering“S”parameter, S21) through the plant and its surrounding space. Therefore, experiments were conducted with tomato plants to examine the potential of using measurements of microwave transmission characteristics for real-time and non-contact monitoring of changes in plants caused by environmental stress. Tomato plants were subjected to water stress in the following environment : 12 h d-1 light period, 26°C/ 19°C (light/dark periods), and 200±10μmol m-2 s-1 PPF at the height of leaves used for measurements of stomatal conductance and photosynthetic rate. Time course changes in the microwave transmission parameter S21 were measured for a tomato plant during water stress, as well as changes in stomatal conductance and photosynthetic rate, which reflect the physiological condition of the plants. S21 parameter measurements were taken over the 1 000 to 3 000 MHz frequency range. Results showed that low frequencies near 1200 MHz were effective for detecting mild levels of water stress while frequencies above 2 400 MHz were effective for detecting moderate to severe levels of water stress.
ISHS International Workshop on Greenhouse Environmental Control and Crop Production in Semi-Arid Regions QUANTITATIVE ESTIMATION METHOD OF PLANT ADAPTATION RESPONSES TO SALINE ENVIRONMENT USING MICROWAVE SENSING
The acclimation of a plant to a constantly changing environment involves the accumulation of certain organic compounds of low molecular mass, known collectively as compatible solutes, in the cytoplasm. Evidence from numerous investigations of plants strongly suggests that glycine betaine (GB), an amphoteric quaternary amine, plays an important role as a compatible solute under various types of environmental stress, such as high levels of salts and low temperature. In this work, sugar beet (Beta vulgaris) was grown at NaCl concentrations of up to 300 mmol/l soil, and the effects of salt on the growth, contents of water, chlorophyll, soluble protein, soluble saccharide and GB in leaf were measured. The addition of NaCl up to 300 mmol/l soil significantly affected the growth, and the contents of water and chlorophyll decreased, whereas the soluble protein and saccharide concentrations in the leaf changed little. On the other hand, the GB concentration increased 6-fold with increasing the salinity of the medium, suggesting that GB is a main osmoprotectant in this plant. The induction of GB was monitored by cultivating the plant seed under salt stress. It was found that the GB originally contained in the seed was lost during the early stage of cultivation, and new GB was synthesized in the stage of germination in a dose-dependent fashion with respect to the salt concentration.
The objective of this research was to experimentally determine whether signs of water deficit stress in plants can be detected from changes in the absorbance spectra based on the relationships between absorbance spectra and physiological parameters. Absorbance of tomato leaves in the near-infrared (NIR) wavelengths (1100 nm to 2500 nm) was measured simultaneously with photosynthesis and stomatal conductance during water stress. To observe small changes in absorbance which arise from water stress, a leaf in non-stressed conditions was used as a reference for the absorbance measurements. In general, under the effects of water stress, peaks formed in the absorbance spectra at water absorbance bands near 1 440 nm and 1 940 nm, and absorbance decreased near 1 600 nm forming a valley. Although the relationship between the changes in absorbance and physiological parameters varied depending on the individual plants tested, consistent overall trends were observed, demonstrating there is potential to nondestructively detect changes in plant condition resulting from water stress by measuring NIR absorbance.
In a rotational machine, unbalance on the rotor is formidable since it causes resonance synchronized with the rotation of the rotor. In order to suppress this unfavorable vibration, we built an active vibration control system of flexible rotor using an electromagnetic damper. Our control system is composed of a digital controller to suppress the rotationally synchronized whirling motion and also a conventional analogue controller. Using our control system, whirling motion of the rotor under various rotating speeds was suppressed significantly.
Organic chemicals such as dioxins arise by the chlorination of an incomplete combustion product in the burning process, heat recovery process, gas cooling process and execution of the incinerator exhaust gas treatment process. Therefore, ‘complete combustion’ should be considered a priority in order to suppress the dioxins in the incineration processing of waste. This study applies to water gas reaction (fuel aided combustion) and strong rotational air flow (gas agitation) so as to achieve complete combustion. Measurements were made of the inside furnace temperature distribution and gas velocity distribution, with the aim of the development of small incinerator that offers total incineration. Further, we experimented with combustion of farm vinyl, adjusted so that the vinyl was mixed with the wood at a ratio of 1:1. As a result, it was confirmed that good combustion was possible and that the generation of dioxins was low.
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