Optimized nested threshold cell discarding for ATM overload control

This paper deals with overload control in asynchronous transfer mode (ATM) networks via priority cell discarding mechanisms governed by a set of nested queue fill thresholds. Specifically, we address the problem of finding the optimal set of discarding thresholds, for an arbitrary number of priorities, under two different performance scenarios. In the first scenario, we minimize the expected discarding cost (a performance penalty) for a given offered load using stochastic dynamic programming. In the second scenario, we maximize the offered load subject to constraints on cell loss (discarding) probabilities using an efficient search technique developed specifically for this problem. Our results illustrate that nested threshold discarding systems can perform significantly better under either scenario than a system without discarding priorities. We characterize the performance advantage over ranges of system parameter values and briefly study the use of sub-optimal, non-adaptive thresholds.     

Dépendance de fréquence de la résistance des couches minces d'aluminium dans la gamme des ondes centimétriques

The dependence of the surface resistivity of thin aluminium films on electric field at microwave frequencies has been studied. It was established that in the frequency range 7.7–37 GHz the resistivity is dependent on structure and either reveals the resonance type of variation or increases with increasing frequency. The capacitance and inductance of a square area in the Al films were determined from the experimental dependence of the resistivity on frequency. It was found that the inductance depends on the dimensions of surface crystalline grains and increases with the mean diameter of the grains. The resistivity of thin aluminium films produced during application of a d.c. field is less dependent on frequency than that of films formed under usual conditions.     

Some formaldehyde reaction products in non-enzymatic browning reactions

Summary The volatiles isolated from the glycine-glyoxal model system were analysed and two compounds derived from formaldehyde (arising from the Strecker degradation of glycine) were identified. The structure of the two compounds, i.e., 2,4,6-trioxaheptane and 2,4,6,8-tetraoxanonane, was confirmed by the analysis of the reference compounds isolated from the commercial formaldehyde solution and analysed by gas chromatography/mass spectrometry and¹H-NMR spectrometry. The above compounds (the reaction products of formaldehyde oligomers with methanol) are described, for the first time, as minor volatiles in non-enzymatic browning reactions.

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Einige Reaktionsprodukte von Formaldehyd in nicht-enzymatischen Bräunungsreaktionen

Zusammenfassung Es wurden aus einem Modellsystem Glycin-Glyoxal flüchtige Stoffe isoliert und zwei Verbindungen, abgeleitet vom Formaldehyd (der durch die Streckersche Reaktion der Degradierung von Glycin entsteht) identifiziert. Die Struktur dieser zwei Verbindungen 2,4,6-Trioxaheptan und 2,4,6,8-Tetraoxanonan wurde durch die Analyse der Referenzverbindungen aus der Lösung von Formaldehyd des Handels bestätigt. Die Analyse wurde mit der Methode MGC/MS and¹H-NMR Spektrometrie vorgenommen. Die oben angeführten Verbindungen (Reaktionsprodukte von Oligomeren von Formaldehyd mit Methanol) wurden zum erstenmal als flüchtige Stoffe in den Reaktionen der nicht-enzymatischen Bräunung beschrieben.

     

Self‐tuning PID controller using δ‐model identification

This contribution presents an application of a self‐tuning digital PID controller for process control modelled by δ‐models. The process is identified by the regression (ARX) model using the recursive least‐squares method (RLSM) with LD decomposition and applied directional forgetting. Controller synthesis is designed on the basis of a modified Ziegler–Nichols criterion for digital PID control loops. The ultimate (critical) proportional gain and period of oscillations have been derived for the second‐order δ‐model. Control results obtained using digital PID controller on the basic δ‐models and z‐models are compared. Copyright © 2002 John Wiley & Sons, Ltd.     

Structure and impact strength of ABS polymers

This paper has dealt with the phenomenal theory describing impact strength as the result of the competition of breaking and yield processes inside the material. Because the breaking processes are not too temperature and deformation speed dependent, they were roughly considered as the one-point constant. The yielding processes were described by means of the EYRING's theory of the absolute reaction rates. From this viewpoint were discussed relations between some structural features of ABS polymers: the chemical composition of rubber, the molecular weight of the S-AN copolymer, the content and degree of the crosslinking of rubber and the degree of grafting. In all cases was achieved a satisfactory agreement between the proposed theory and the experiment.     

Complex Positive Effects of SGLT-2 Inhibitor Empagliflozin in the Liver,Kidney and Adipose Tissue of Hereditary Hypertriglyceridemic Rats: Possible Contribution of Attenuation of Cell Senescence and Oxidative Stress

(1) Background: empagliflozin, sodium-glucose co-transporter 2 (SGLT-2) inhibitor, is an effective antidiabetic agent with strong cardio- and nephroprotective properties. The mechanisms behind its cardio- and nephroprotection are still not fully clarified. (2) Methods: we used male hereditary hypertriglyceridemic (hHTG) rats, a non-obese model of dyslipidaemia, insulin resistance, and endothelial dysfunction fed standard diet with or without empagliflozin for six weeks to explore the molecular mechanisms of empagliflozin effects. Nuclear magnetic resonance (NMR)-based metabolomics; quantitative PCR of relevant genes involved in lipid and glucose metabolism, or senescence; glucose and palmitic acid oxidation in isolated tissues and cell lines of adipocytes and hepatocytes were used. (3) Results: empagliflozin inhibited weight gain and decreased adipose tissue weight, fasting blood glucose, and triglycerides and increased HDL-cholesterol. It also improved insulin sensitivity in white fat. NMR spectroscopy identified higher plasma concentrations of ketone bodies, ketogenic amino acid leucine and decreased levels of pyruvate and alanine. In the liver, adipose tissue and kidney, empagliflozin up-regulated expression of genes involved in gluconeogenesis and down-regulated expression of genes involved in lipogenesis along with reduction of markers of inflammation, oxidative stress and cell senescence. (4) Conclusion: multiple positive effects of empagliflozin, including reduced cell senescence and oxidative stress, could contribute to its long-term cardio- and nephroprotective actions.     

Extraction of boundary representation from surface triangulations

Many computational science tools employ finite element meshes as discretizations of the geometrical domains, and automatic mesh generation has become an indispensable part of the discretization process. Boundary representations (BRep) of solids are the means of describing the geometrical model to the mesher, thus enabling the generator to proceed without user intervention. Significant effort has been devoted in the past to BRep construction in the frame‐work of solid modelling systems. In this paper we consider the task of converting a tesselation (triangulation) of the surface of a solid into a BRep, and propose a robust and efficient set of algorithms for this purpose. Applications include, among others, remeshing of finite element discretizations during simulations involving not only geometric distortion but also changes in topology (coalescence and fragmentation of solids, flow, and so on). Copyright © 2001 John Wiley & Sons, Ltd.