On the reduction of repetitive processes into singular and non-singular Roesser models

Multidimensional Systems and Signal Processing - In this paper we present new methods for the reduction of a polynomial system matrix describing a discrete linear repetitive process, to equivalent...     

Sub-optimal solutions to track detection problem using graph theoretic concepts

This paper demonstrates how the problem of tracking targets, which appear as either straight or curved lines in two-dimensional display images (or data images) can be formulated in terms of a directed weighted graph model and how dynamic programming techniques can be efficiently applied to reach an optimal or sub-optimal solution. In general, track detection algorithms providing optimal solutions have good detective ability, but most of them suffer from the inability to detect discontinuous lines or to resolve efficiently pairs of crossing lines. A sub-optimal solution is provided that efficiently overcomes these weaknesses. We focus on modeling the track detection problem in terms of a graph, formulating fast sequential/parallel sub-optimal track detection algorithms and testing them on simulated data in order to show their detective ability. Moreover, we specify the conditions under which sub-optimal algorithms can perform at least as well as their corresponding optimal algorithms. This is significant for the track detection problem where fast, accurate and real-time detection is considered a necessity.     

Mathematical simulation and experimental verification of melting resulting from the coupled effect of natural convection and exothermic heat of mixing

When melting processes are associated with an exothermic heat of mixing, unique coupled transport phenomena take place. In this article, a mathematical model has been developed to simulate these unique coupled heat and mass transfer events. The model was based on the control-volume finite difference approach and on an enthalpy method. In order to verify the mathematical model, a low-temperature physical model was established consisting of ice and sulfuric acid solutions. In this physical model, both temperature and velocity measurements were carried out. The model predictions were compared with experimental measurements, and they were found to be in good agreement. The model was also applied to a high-temperature system, namely, the melting of silicon metal in liquid high carbon iron. The predictions distinguished two periods present in the entire melting process. In the first period, the silicon was heated up. The second period, i.e., free melting period, occurred in tandem with the exothermic reaction, and consequently, the melting process was greatly accelerated. As was the case with the low-temperature physical model, as with the high-temperature system, good agreement was obtained between the predicted results and the experimental measurements.     

The Solution kinetics of zirconium in liquid steel

Zirconium cylinders were immersed into liquid steel and their mass-transfer rates were measured under static and dynamic conditions. The cylinders were suspended from a load cell, and the apparent weight of the dissolving specimen as well as temperatures at various locations in the samples were measured continuously during immersion and recorded with a data acquisition System. From the weight measurements, the mass-transfer rate was deduced. In the assimilation of zirconium in liquid steel two periods were identified, i.e. the steel shell period and the free dissolution period. Immediately upon immersion the steel shell period Starts and when this period ends the free dissolution period commences. During the steel shell period, a shell of frozen steel wraps around the cylinder following its initial immersion. When zirconium cylinders were immersed into liquid steel, a reaction was detected at the steel shell/zirconium interface. This reaction took place almost immediately after immersion. The intermetallic Compounds Fe₂Zr and FeZr₂ were identified as reaction products. The experimentally measured mass transfer rates during the free dissolution, under quiescent and inductively stirred steel baths, were very similar. Under the experimental conditions used, the rate Controlling step of zirconium dissolution in liquid steel is reaction controlled.     

Intraoperative blood salvage in children and young adults undergoing spinal surgery with predeposited autologous blood: efficacy and cost effectiveness

We conducted a retrospective review of 155 spinal operations at our institution to determine the efficacy of intraoperative salvage. Addition of intraoperative salvage had little effect on the success of a preoperative autologous donation program. Only patients with operative blood loss > 2,000 ml (12% of patients) benefited from this expensive source of autologous blood. The technique tended to be most effective in children aged 16-18 years. Use of intraoperative salvage for all pediatric spinal procedures is neither necessary nor cost effective.     

Evaluating Liquefaction Strength of Partially Saturated Sand

A method is presented for evaluating the liquefaction strength of partially saturated sand using the compression wave velocity (P-wave velocity), a new indicator of saturation. Based on laboratory test results, an empirical correlation that relates the liquefaction strength with the pore pressure coefficient B is firstly proposed. The strength is defined as the cyclic stress ratio required to cause liquefaction at a specified number of cycles. With the aid of a theoretical relation between B and the P-wave velocity, an explicit correlation of more interest is then established between the liquefaction strength of sand and its P-wave velocity. A comparison of the predictions using this explicit correlation with laboratory measurements shows a satisfactory agreement. The significance of this method lies in that it makes it possible to evaluate the liquefaction strength of sand as affected by saturation through the measurement of P-wave velocity, which can be made not only in the laboratory but particularly in the field.     

Representation and uniformization of algebraic transductions

This paper explores different means of representation for algebraic transductions, i.e., word relations realized by pushdown transducers. The relevance of this work lies more in its point of view rather than any particular result. We are aiming at giving specific techniques for obtaining, or perhaps explaining, decompositions of algebraic (and incidentally, rational) relations, relying solely on their “machine” definition rather than some complex algebraic apparatus. From this point of view, we are hoping to have demystified the heavy formalism employed in the present literature. Some of the novelties of our work are: the use of “stack languages” and “embeddings,” which eliminate the need of arbitrary context-free languages in our characterizations, the study of uniformizations for algebraic transductions and the use of the so-called stack transductions for exposing the anatomy of pushdown transducers.This work was supported by the Natural Science and Engineering Research Council of Canada grants R220259 and OGP0041630.     

Double-diffusive convection in a circular cylinder

Summary A theoretical study is made of the onset of steady double-diffusive convection in a circular cylinder of small to moderate aspect ratio. An eigenfunction expansion method is used to derive systems of amplitude equations for weakly nonlinear evolution of critical disturbances. It is shown that the nature of the convective solution near criticality depends strongly on the cylinder's aspect ratio; this is particularly the case at or near aspect ratios where two modes become unstable at the same Rayleigh number. There is also a strong dependence on Prandtl number, which is discussed.With 7 Figure     

Characterisation of Moringa stenopetala seed oil variety “Marigat” from island Kokwa

The oil from Moringa stenopetala seeds variety Marigat from the island Kokwa was extracted using 3 different procedures including cold press (CP), extraction with n‐hexane and extraction with a mixture of chloroform:methanol (1:1) (CM). The yield of oil was 35.7% (CP) to 44.9% (CM). The density, refractive index, colour, smoke point, viscosity, acidity, saponification value, iodine value, fatty acid methyl esters, sterols, tocopherols (by high‐performance liquid chromatography), peroxide value, Eequation/tex2gif-stack-1.gif at 232 nm and the susceptibility to oxidation measured by the Rancimat method were determined. The oil was found to contain high levels of unsaturated fatty acids, especially oleic (up to 76.40%). The dominant saturated acids were behenic (up to 6.01%) and palmitic (up to 6.21%). The oil was also found to contain high levels of β‐sitosterol (up to 52.19%%of total sterols), stigmasterol (up to 16.53% of total sterols) and campesterol (up to 14.26% of total sterols). α‐, β‐ and δ‐tocopherols were detected up to levels of 98.00, 44.50 and 82.41 mg/kg of oil, respectively. The reduction of the induction period (at 120 °C) of M. stenopetala seed oil ranged from 29.4% to 54.7% after degumming. The M. stenopetala seed oil showed high stability to oxidative rancidity. The results of all the above determinations were compared with those of a commercial virgin olive oil and Moringa oleifera seed oil.     

A STUDY ON THE SEPARATION OF DIFFUSION AND SURFACE EMISSION COEFFICIENTS IN WOOD

For a more accurate simulation of the moisture sorption process in wood, the precise separation of surface emission and diffusion coefficients is essential. In this paper, a non-linear simplex technique that was developed to obtain the optimum pair of the surface emission coefficient he, and the diffusion coefficient D from a single sorption curve is presented and tested with experimental data. An easy to use computer program was employed to carry out the evaluation. Data analysis showed that the new method resulted in a more statistically accurate calculation of b_c and D than currently existing methods.