Compress sensing algorithm for estimation of signals in sensor networks

Wireless Networks - In this research, we present a data recovery scheme for wireless sensor networks. In some sensor networks, each node must be able to recover the complete information of the...     

Separating the reaction and spark plasma sintering effects during the formation of TiC–Cu composites from mechanically milled Ti–C–3Cu mixtures

The goal of this work was to separate the reaction and spark plasma sintering (SPS) effects during the in-situ synthesis of TiC in mechanically milled Ti–C–3Cu powder mixtures. The powders were milled for 3–10 min in a high-energy planetary ball mill. Structural changes occurring in the reaction mixtures during thermal explosion (TE) in a furnace and SPS in a graphite die were compared. Although the maximum temperature of TE reached the melting point of copper in some samples, no evidence of extensive melting was observed in the microstructure of the products of TE. The ignition and maximum temperatures of TE were found to decrease with increasing milling time of the mixture. In the mixture milled for 10 min, the maximum temperature of TE was only 820 °C. Melting of copper at the inter-particle contacts during SPS was observed in samples milled for 5–10 min (SPS at 900–980 °C) and caused the formation of TiC-depleted regions in the microstructure. Those regions were the re-solidified melt partially filling the pores between the agglomerates. Based on the analysis of the TE parameters in the mixtures and microstructures of the products of TE and SPS, melting during SPS was attributed to the effect of electric current (a high electric current density at the inter-particle contacts) and not to the heat of reaction. The hardness, compressive strength and Young's modulus of the sintered composites are reported. A TiC–Cu composite (milling time 5 min, SPS at 980 °C, relative density 93%) shows a compressive yield strength of 890 MPa and an ultimate compressive strength of 920 MPa.     

Metal hydride hydrogen storage and compression systems for energy storage technologies

Along with a brief overview of literature data on energy storage technologies utilising hydrogen and metal hydrides, this article presents results of the related R&D activities carried out by the authors. The focus is put on proper selection of metal hydride materials on the basis of AB₅- and AB₂-type intermetallic compounds for hydrogen storage and compression applications, based on the analysis of PCT properties of the materials in systems with H₂ gas. The article also presents features of integrated energy storage systems utilising metal hydride hydrogen storage and compression, as well as their metal hydride based components developed at IPCP and HySA Systems.     

Physicomathematical Modeling of Explosive Dispersion of Liquid and Powders

Studies have been conducted with respect to the generation of fine‐disperse aerosols with the use of an explosive disperser model based on hydrodynamic shock tube. The physicomathematical model for the process of explosive dispersion with the aforesaid design is described [1]. The use of elements in the model design to produce cavitation bubbles under the action of shock wave and ensurance of slower outflow process of a water‐steam mixture makes it possible to obtain liquid disperse aerosols. The experimental results for aerosol disperse parameters and the processes of initiation and propagation of an aerosol cloud produced upon explosive dispersion of a variety of liquids and condensed powders are presented. Pressure values in the combustion chamber of the disperser, velocity of aerosol particles, and aerosol disperse parameters were obtained. The design of the explosive disperser with a nozzle, which provides favorable conditions for cavitation processes inside the dispersed liquid, is shown to allow the generation of a high dispersity aerosol (about 1–100 nm), which is essential for many practical problems. The function of distribution of such particles by size cannot be measured reliably and directly by methods available; however, indirect experiments (measurement of humidity when dispersing water) permit estimating the existence of particles in the aerosol with sizes below 1 μm in quantity of approx. 90 %.     

Methods for activating the decision-making process that is used for controlling flexible manufacturing systems

This paper deals with controlling flexible manufacturing systems (FMS) operating in volatile production environments. Shnits et al. (Shnits, B., Rubinovitz, J., and Sinreich, D., 2004. Multicriteria dynamic scheduling methodology for controlling a flexible manufacturing system. International Journal of Production Research, 42 (17), 3457–3472.) and Shnits and Sinreich (Shnits, B. and Sinreich, D., 2006. Controlling flexible manufacturing systems based on a dynamic selection of an appropriate operational criteria and scheduling policy. International Journal of Flexible Manufacturing Systems, 18 (1), 1–27.) developed a multi-criteria dynamic scheduling mechanism for controlling an FMS that can cope with such environments. An important part of this mechanism functioning, which impinges directly on its performance, is the activation of its decision-making process. This study continues the research presented in the above-mentioned papers and proposes different triggering methods for activating the control system decision-making process. The operational conditions for each suggested triggering method were analysed and a comparative analysis between these methods was performed. It was revealed that the highly dynamic triggering method, which activates the decision-making process right before a resource becomes available, outperformed the triggering methods that use a predefined scheduling period.     

Paschen testing of ITER prototype cryogenic axial breaks

Axial insulation breaks are needed in forced cooled cryogenic high voltage devices for the separation of the high voltage area from the grounded pipe system. The ITER cryogenic axial breaks will be surrounded by good vacuum in case of normal operation but also under vacuum breakdown conditions sufficient dielectric strength is required for a reliable fast discharge of the coil system. A Paschen tight design of the ITER prototype breaks enables high voltage operation independent on the outer vacuum or gas conditions. Consecutively two pretested ITER prototype breaks were integrated in the insulation system of a Paschen test unit and high voltage tested. Two different ways to perform the Paschen testing were used for both breaks. The preparation of the breaks and the test setup are described and the test results are given.     

Model Investigations on the Stability of the Steel-Slag Interface in Continuous-Casting Process

In the continuous-casting mold, the mold powder in contact with the liquid steel surface forms a liquid slag layer. The flow along the steel-slag interface generates shear stress at the interface, waves, and leads to fingerlike protrusions of liquid slag into steel. Reaching a critical flow velocity and thereby shear stress, the protrusions can disintegrate into slag droplets following the flow in the liquid steel pool. These entrained droplets can form finally nonmetallic inclusions in steel material, cause defects in the final product, and therefore, should be avoided. In the current work, the stability of a liquid-liquid interface without mass transfer between phases was investigated in cold model study using a single-roller driven flow in oil-water systems with various oil properties. Applying the similarity theory, two dimensionless numbers were identified, viz. capillary number Ca and the ratio of kinematic viscosities ν ₁/ν ₂, which are suitable to describe the force balance for the problem treated. The critical values of the dimensionless capillary number Ca^* marking the start of lighter phase entrainment into the heavier fluid, are determined over a wide range of fluid properties. The dimensionless number ν ₁/ν ₂ was defined as the ratio of kinematic viscosities of the lighter phase ν ₁ and heavier phase ν ₂. The ratios of kinematic viscosities of different steel-slag systems were calculated using measured thermophysical properties. With the knowledge of thermophysical properties of steel-slag systems, Ca^* for slag entrainment as a function of v ₁/v ₂ is derived. Assuming no reaction between the phases and no interfacial flow, slag entrainment should not occur under the usual casting conditions.