Direct transformation of nonlinear systems into state affine MISO form for observer design

This paper gives necessary and sufficient conditions to solve in a constructive way the transformation of a general multiple-input-single-output nonlinear system into a state affine system. This result is direct i.e., without solving the state elimination problem when computing the input-output differential equation. A Kalman-like observer can be designed for the obtained state affine system.     

The behavior of a cloud of emissions of high moisture content in the surface layer of the atmosphere

The propagation in the atmosphere of instantaneous emissions which largely consist of water vapor is treated in a three-dimensional formulation. The regularities are studied of the evolution of the hydrodynamic, concentration, and temperature fields depending on the parameters which define the state of the atmosphere (temperature and humidity), as well as on the temperature and moisture content of the cloud of emissions.     

Mycological survey for potential aflatoxin and ochratoxin producers and their toxicological properties in harvested Brazilian black pepper.

A mycological survey was carried out on 115 samples of whole dried black pepper seeds, from two main production regions of Brazil (Pará and Espírito Santo). A high incidence of contamination was verified in both regions when 99.1% of the samples showed filamentous fungi contamination. A total of 497 species of nine different genera were isolated (Aspergillus, Eurotium, Rhizopus, Penicillium, Curvularia, Cladosporium, Absidia, Emericella and Paecilomyces). The genus Aspergillus was the predominant (53.5%) followed by species from the Eurotium genus (24.5%). Eurotium chevalieri (16.4%) was the most predominant species followed by A. flavus (14.6%) present on 55 samples of black pepper (47.8%) analysed. Twenty-five samples (21.7%) were contaminated with aflatoxigenic strains of A. flavus and A. parasiticus. In relation to the types of aflatoxins produced by mycotoxigenic strains, it was observed that 25 strains (44.6%) of 56 isolated of A. flavus produced aflatoxins. From 12 samples, A. ochraceus species were isolated in low frequency (3.5%). Two strains of A. ochraceus from 16 isolated were producers of ochratoxin A. With respect to the aflatoxins and ochratoxin A natural contamination, none of the samples presented detectable levels of these mycotoxins using thin-layer chromatographic analysis.     

The effect of the scale of horizontal subsurface flow constructed wetlands on flow and transport parameters.

Horizontal subsurface flow constructed wetlands have proven their efficiency in treating wastewater and removing the pollutants of concern. Treatment efficiency depends on the wastewater residence time, which is a function of the hydraulic loading and the physical conditions of the constructed filter system, which can be described with effective parameters such as: hydraulic conductivity, porosity, dispersivity etc. Because spatial variability is often scale dependent, these effective parameters may be affected by the scale of the system being studied. In this paper the results of tracer experiments in constructed filters using saturated horizontal flow at three scales (small and medium lab scales and full-scale system) using the same filter media is reported. Light-weight aggregate (filter media termed Filtralite-P) was used at all scales. Increasing the scale was associated with increasing dispersivity, meanwhile hydraulic conductivity experienced dramatic reduction and variation by increasing the examined scale. Observed changes in the hydraulic parameters indicate that heterogeneity at different scales should be taken into account when the performance of LWA filters are evaluated from small-scale experiments.     

Thermodesorption of samarium from oxidized tungsten surface

Thermodesorption of samarium (Sm) atoms and samarium oxide (SmO) molecules from samarium films deposited in vacuum onto tungsten substrates covered with thin (<1 nm thick) layers of tungsten oxides has been studied. It is established that samarium reduces tungsten from its oxides. The parameters of Sm and SmO desorption from an oxidized tungsten surface are determined.     

Survey of nitrate and nitrite contents of vegetables grown in Korea.

A scientific basis for the evaluation of the risk to public health arising from excessive dietary intake of nitrate in Korea is provided. The nitrate () and nitrite () contents of various vegetables (Chinese cabbage, radish, lettuce, spinach, soybean sprouts, onion, pumpkin, green onion, cucumber, potato, carrot, garlic, green pepper, cabbage and Allium tuberosum Roth known as Crown daisy) are reported. Six hundred samples of 15 vegetables cultivated during different seasons were analysed for nitrate and nitrite by ion chromatography and ultraviolet spectrophotometry, respectively. No significant variance in nitrate levels was found for most vegetables cultivated during the summer and winter harvests. The mean nitrates level was higher in A. tuberosum Roth (5150 mg kg(-1)) and spinach (4259 mg kg(-1)), intermediate in radish (1878 mg kg(-1)) and Chinese cabbage (1740 mg kg(-1)), and lower in onion (23 mg kg(-1)), soybean sprouts (56 mg kg(-1)) and green pepper (76 mg kg(-1)) compared with those in other vegetables. The average nitrite contents in various vegetables were about 0.6 mg kg(-1), and the values were not significantly different among most vegetables. It was observed that nitrate contents in vegetables varied depending on the type of vegetables and were similar to those in vegetables grown in other countries. From the results of our studies and other information from foreign sources, it can be concluded that it is not necessary to establish limits of nitrates contents of vegetables cultivated in Korea due to the co-presence of beneficial elements such as ascorbic acid and alpha-tocopherol which are known to inhibit the formation of nitrosamine.     

Concept and salient design features of a high-temperature nuclear reactor with solid coolant

The salient features of using a solid substance to cool the core of a nuclear reactor and the associated advantages and limitations are examined. Conceptual proposals concerning the core design and the arrangement of the in-reactor space of a high-temperature nuclear reactor with a solid coolant are presented. Evaluated data and some results for a model reactor are presented. __________ Translated from Atomnaya énergiya, Vol. 103, No. 3, pp. 156–161, September, 2007.     

Solution of the stochastic H ∞-optimization problem for discrete time linear systems under parametric uncertainty

The stochastic H _∞-optimization problem for a linear discrete time system with uncertain parameters is formulated and solved. The system operates in the presence of Gaussian random disturbances. The original problem with parametric uncertainty is reduced to the stochastic H _∞-optimization problem without uncertainty and having one extra input, which is essentially the mixed H ₂/H _∞-optimization problem. In a sense, the problem considered in this paper incorporates the classical H ₂/H _∞-and H _∞-optimization problems as limiting cases.     

Self-excitation and synchronization in a multibeam microwave generator with electron-oscillator flows

Self-excitation and radiation of a multibeam spatially distributed microwave generator with centrifugal electrostatic focusing are considered. The transition to equivalent self-oscillators with slowly varying amplitudes and phases is substantiated. Examples of the directivity patterns and level lines of the field radiated in the master-slave and mutual synchronization modes and observed in a given section are presented.