Model reduction for robust control: A schur relative error method

A numerically robust relative error method for state-space model order reduction is described. Our algorithm is based on Desai's balanced stochastic truncation technique for which Green has obtained an L^∞ relative error bound. However, unlike previous methods, our Schur method completely circumvents the numerically delicate initial step of obtaining a minimal balanced stochastic realization of the power spectrum matrix G(s)G^T(?s).     

Effect of a thin <Emphasis Type="Italic">a</Emphasis>-SiO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>: H film on plasmonic properties of gold nanoparticles

Data on the optical properties of a nanocomposite material constituted by gold nanoparticles covered with a thin film of amorphous hydrogenated silicon suboxide have been obtained for the first time. The thin film was deposited by gas-jet electron-beam plasma chemical-vapor deposition. As gold particles situated on the surface of quartz glass are covered with a thin a-SiO _x : H film, their plasmonic resonance peak is shifted to longer wavelengths. The calculations made in the study demonstrated a good agreement with the experiment.     

Microbiological treatment of oil-containing radioactive waste prior to cementation

Microbiological oxidation of liquid organic radioactive waste (ORW), spent vacuum and transformer oils, is described. The physicochemical properties of oils and their structural-group composition before and after using in the process cycle were studied. Changes in the structural-group composition and physicochemical parameters of oils upon microbiological treatment were determined. The distribution of radionuclides between the organic and aqueous phases upon microbiological treatment was studied by the example of model ORW containing ¹³⁷Cs, ⁹⁰Sr, ²³⁸Pu, and ²⁴¹Am. The compatibility of oils subjected to microbiological treatment with the cement compound intended for ORW disposal was evaluated. The biological step of the radioactive oil processing leads to a decrease in the weight and volume of the organic radioactive waste and increases its amount that can be incorporated into the cement compound (to 30 vol %) without deterioration of the strength characteristics of the cement.     

Characteristics of the neutron field at the core center in the ИBB-2M water-moderated water-cooled reactor

The neutron spectrum has been measured at the center of the core in the ИBB-2M research water-moderated water-cooled reactor. A technique has been developed to measure the energy spectrum of neutrons in high-intensity fields (with a flux density of >10¹² cm^?2 s^?1) without recourse to fission detectors enclosed in boron shields.     

Physarum computing and topology optimisation

The plasmodium stage of the giant single-celled amoeboid organism Physarum polycephalum, or true slime mould, dynamically adapts its body plan in response to environmental stimuli, including nutrient location, temperature gradients, light exposure, and predatory threats. The construction and adaptation of the plasmodial transport network has been shown to be an efficient trade-off between minimising network distance and maximising connectivity. Optimisation of topology is also a desired trait in manufacturing and engineering, whereby the topology of an initially simple component is modified to minimise one or more properties (for example minimising the amount of substrate reduces the weight and material cost of the component) whilst maintaining other desired material properties within the component (for example strength under specific load points and conditions). Biologically inspired approaches to certain specific engineering challenges are well documented and successful. In this paper we explore at a more general level whether a cross-pollination can occur between Physarum computing and Topology Optimisation. Using an interdisciplinary modelling approach we explore whether the evolution of transport networks in a multi-agent model of Physarum has any similarities to networks formed by Topology Optimisation. We find that the Topology Optimisation method generates networks which are similar to the model slime mould networks. The Topology Optimisation networks correspond to higher regions of the Toussaint hierarchy of proximity graphs (i.e. more edges) whereas the model slime mould networks exhibit greater minimisation of network length. Since it is possible to adjust network connectivity in the multi-agent model via nutrient concentration we speculate that similar parametric adjustment may be possible to alter the connectivity of Topology Optimisation networks.     

Structure and microhardness of the surface layers of iron-carbon alloys after laser heat treatment

Laser radiation is widely used for heat treatment of surfaces of parts. Its special features consist in localizability of the treatment zone, the possibility of strengthening rather inaccessible regions, and, in some cases, elimination of the tempering operation. For the laser treatment to be highly efficient we need data on the effect of the regime and type of laser on the properties of surfaces of various steels and alloys, which are rather scarce in the literature. The aim of the present work consists in analyzing and generalizing results obtained in investigations of the structure and structural and phase transformations in treatment of steels and cast irons by radiation of various lasers.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 20–25, February, 1996.     

Adaptive power control for wireless networks using multiple controllers and switching

Controlling transmitted power in a wireless network is critical for maintaining quality of service, maximizing channel utilization and minimizing near-far effect for suboptimal receivers. In this paper, a general proportional-integral-derivative (PID) type algorithm for controlling transmitted powers in wireless networks is studied and a systematic way to adapt or tune the parameters of the controller in a distributed fashion is suggested. The proposed algorithm utilizes multiple candidate PID gains. Depending on the prevailing channel conditions, it selects an optimal PID gain from the candidate gain set at each instant and places it in the feedback loop. The algorithm is data driven and can distinguish between stabilizing and destabilizing controller gains as well as rank the stabilizing controllers based on their performance. Simulation results indicate that the proposed scheme performs better than several candidate controllers, including a well known distributed power control (DPC) algorithm.     

Photochemical Synthesis of Silver Hydrosol Stabilized by Carbonate Ions and Study of Its Bactericidal Impact on Escherichia coli: Direct and Indirect Effects

The great attention paid to silver nanoparticles is largely related to their antibacterial and antiviral effects and their possible use as efficient biocidal agents. Silver nanoparticles are being widely introduced into various areas of life, including industry, medicine, and agriculture. This leads to their spreading and entering the environment, which generates the potential risk of toxic effect on humans and other biological organisms. Proposed paper describes the preparation of silver hydrosols containing spherical metal nanoparticles by photochemical reduction of Ag⁺ ions with oxalate ions. In deaerated solutions, this gives ~10 nm particles, while in aerated solutions, ~20 nm particles with inclusion of the oxide Ag₂O are obtained. Nanoparticles inhibit the bacterium Escherichia coli and suppress the cell growth at concentrations of ~1 × 10⁻⁶–1 × 10⁻⁴ mol L⁻¹. Silver particles cause the loss of pili and deformation and destruction of cell membranes. A mechanism of antibacterial action was proposed, taking into account indirect suppressing action of Ag⁺ ions released upon the oxidative metal dissolution and direct (contact) action of nanoparticles on bacterial cells, resulting in a change in the shape and destruction of the bacteria.     

To the problem of steel desulfurization in a ladle-furnace unit and a chamber degasser

The laws of deep steel desulfirization in a ladle upon treatment in a ladle-furnace unit and after degassing are considered. On the basis of experiments, a mechanism is proposed for extraction refining by slag with allowance for the role of drop formation in the zone of gas jet outlet. The mechanism consists of several consecutive stages. Under vacuum, the process of stirring with an inert gas substantially enhances the desulfurization rate and can be restricted only by too intense steel cooling and in the absence of a free wall margin in a steel-teeming ladle.