A Nonlinear Filtering Scheme for Multistage Statistically Uncertain Systems

A filtering scheme for multistage systems under uncertain probability distributions of perturbations is studied. A recurrent scheme for constructing point state estimates is designed and its relation with guaranteed filtering theory is determined. This scheme covers the case in which both uncertain and random perturbations are present.     

Pulse-Frequency Characteristics in Bifurcation Problems

Generation of self-oscillations under unstable stationary states of nonlinear control systems, which may contain delay of complicated nature (the Andronov–Hopf bifurcation), and approximate design of self-oscillating states and their asymptotes are studied with the help of pulse-frequency characteristics of the linear component of a system.     

Integrated optimization of the use of information and hardware resources in data processing systems with controllable message size

The paper considers integrated optimization of a single-server semi-Markov queue with input conflicts, controllable message size, and a finite buffer with different types of storage organization. The optimization is based on an additive performance criterion.Translated from Kibernetika i Sistemnyi Analiz, No. 6, pp. 45–53, November–December, 1991.     

Oxidation of porous nanocrystalline titanium nitride. II. Scale structure and composition

We have used x-ray phase analysis to study the composition of the products of reaction between oxygen and nanocrystalline powders with particle sizes 15, 40, 55, and 80 nm, and also specimens pressed (and sintered) from them. The powders were oxidized in air at 100°C (400 h) to 500°C (5 min), while the sintered specimens were oxidized at 600–900°C for 15, 120, and 240 min. In all cases, in the initial oxidation step the oxynitride Ti(O_xN_y) is formed, which over time is oxidized to TiO, Ti₂O₃, Ti₃O₅, TiO₂ (anatase) and TiO₂ (rutile). In the range 600–800°C, formation of a continuous oxide layer and conversion of anatase to rutile slows down diffusion of oxygen in the scale. We have established that at 900°C, the growth rate of the scale thickness increases and so the reflections from the oxynitride are barely noticeable on the diffraction patterns taken from the surface of the oxidized specimen. In these diffraction patterns, along with strong reflections from the rutile, we also observed weak reflections from lower oxides and anatase, which may be due to reaction between oxygen and the titanium ions diffused to the scale surface. We have concluded that at T > 850°C, the mechanism for oxidation of TiN changes. This is due to superposition of counterdiffusion of titanium ions on the diffusion of oxygen. __________ Translated from Poroshkovaya Metallurgiya, Nos. 3–4(448), pp. 72–78, March–April, 2006.     

The effects of deep zones on wetland nitrogen processing.

Twelve research wetlands were operated under varying conditions at a site west of the city of Phoenix. These were constructed as a triplicated design, with zero, one, two and three internal deep zones, all containing an inlet distribution and an outlet collection deep zone, together comprising 12.5-35% of the wetland areas. The water supply was partially nitrified effluent from a city wastewater treatment plant. Total nitrogen was reduced by about 50%, from inflow concentrations between 6 and 8 mg/L. Speciation of the inflow was approximately 25% organic nitrogen, 25% ammonium nitrogen and 50% nitrate nitrogen. Typical outflow concentrations were about 1.2 mg/L organic, 0.5 mg/L ammonium and 0.0-2.5 mg/L nitrate. Rate constants for total nitrogen were 15-20 m/year at 20 degrees C, and 20-30 m/year for nitrate, which agree well with other project reports. Temperature factors averaged 1.100 for total nitrogen, and 1.184 for nitrate. There were no differences in the internal hydraulics with deep zone numbers. Deep zone numbers in the wetlands did not affect nitrogen treatment performance. No differences with deep zone numbers were found for temperature, dissolved oxygen, pH, or nitrogen removals or rate constants. In conjunction with other reported results, there appears to be no large treatment benefit or detriment of incorporating internal deep zones in free water surface wetlands.     

Colloidal silica removal in coagulation processes for wastewater reuse in a high-tech industrial park.

Four experiments of coagulation and flocculation were conducted to investigate the characteristics of colloidal silica removal in a high-tech industrial wastewater treatment plant for reclamation and reuse of the effluent. Experimental results illustrated that poly-aluminium chloride (PACl) showed higher performances on colloidal silica removal than alum. Interestingly, the two coagulants demonstrated the same capacity on silica removal. The specific silica removal capacity was approximately 0.135 mg SiO2/mg Al2O3 when the dosage of coagulants was in the range 30-150 mg/L Al2O3. In addition, the silica was reduced significantly at the condition of pH above 8. Experimental data implied that precipitation of aluminium flocs was the major mechanism for colloid silica removal in PACl and alum coagulation, besides, charge adsorption was also important for improving removal efficiency. Moreover, the addition of polyacrylic acid (PAA) as a flocculant could slightly advance silica removal in the PACl coagulation. The combined PACl/PAA/flocs coagulation was effective for the removal of colloidal silica, soluble COD, and turbidity and also suitable as a pretreatment unit in wastewater reclamation and reuse processes.     

Mössbauer spectroscopic studies of Fe-substituted YIG

Compositional dependence of hyperfine parameters, determined through Mössbauer spectral analysis has been studied for Y_3−xFe_5+xO₁₂ (x = 0.0, 0.1, 0.3 and 0.5) garnet system at 300 K. The Mössbauer spectra have been fitted with three sextets in the ferrimagnetic state corresponding to Fe³⁺ ions at tetrahedral (d), octahedral (a) and dodecahedral (c) sites of the crystal structure. It is observed that isormershift, quadrupole shift and hyperfine field of d-site show no significant variation with Fe³⁺ concentration. The change in hyperfine fields of a- and c-sites with composition (x) has been explained on the basis of strength of exchange integrals, change in isomershift can be understood due to s-electron charge distribution and asymmetric displacement of oxygen ions surrounding the a- and c-sites seems to be responsible for observable quadrupole shift. The magneton number values obtained from magnetization and Mossbauer data are in agreement to those calculated using Neel's three sublattice model of ferrimagnetism.