On the robust control of nonlinear systems

In this paper we consider robust stabilization of the class of nonlinear plants of the form $$\dot x = f(x) + \sum\limits_{i = 1}^m {g_i } (x)u_i (t),$$ which are equivalent, under smooth state space coordinate transformations and nonlinear state feedback, to controllable systems. This approach is very sensitive for unknown parameters' values. Parameter adaptation may be used as a technique to robustify minimum-phase systems [3]. We give an example of a locally stable adaptive tracking system in which the last assumption is weakened. The minimum-phase plant considered in the paper is a current-controlled squirrel cage induction motor.     

The Dynamic Structure Factor of 4He beyond the Roton Minimum

The dynamic structure factor S( , ) of ⁴ He is studied at zero temperature in the momentum region at and above the roton minimum by field-theoretical methods. The model is derived from the Gavoret-Nozières (GN) two particle propagator by introducing the concept of quasiparticles. In this way a connection between the field theory of GN and the phenomenological models of Zawadowski-Ruvalds-Solana (ZRS) type is obtained. An improved expression for the dynamic structure factor within ZRS-like models is found. Numerical results for S( , ) are presented for momentum and energy independent effective interactions between quasiparticles.     

X-ray microanalysis and properties of multicomponent plasma-borided layers on steels

The structure and chemical composition of composite and multicomponent borided layers obtained by a new method that combines the chemical electroless and plasma boriding techniques are described. Quantitative X-ray microanalysis examinations show that on the surface of nickel–phosphorus coated steel borided at 923 K three boride phases of the type (Ni _x Fe_{1 – x} )₄B₃, (Ni _x Fe_{1 – x} )₂B and (Fe _x Ni_{1 – x} )B formed, whereas in the samples borided at 1123 K only two borides (Fe_{1 – x} Ni _x )B and (Fe_{1 – x} Ni _x )₂B are present. The shape and the distribution of the phases depends on the thickness of the Ni–P layer deposited on the steel substrate before boriding. The thicknesses of boride zones obtained on nickel coated steels are much greater than those obtained on the same steel without nickel coating. Also the diffusion zone between the Ni–P layer and the steel increases during boriding, which improves the adhesion of the layer to the substrate. The composite layers obtained show a high wear resistance, with their resistance to corrosion being markedly greater than that of uncoated and only borided steel.     

Relationship Between the Thermodynamic Parameters,Structure, and Anticorrosion Properties of Al-Zr-Ni-Fe-Y Alloys

Metallurgical and Materials Transactions A - The influence of the chemical composition on the crystallization process, amorphous phase formation, and the anticorrosion properties of Al-Zr-Ni-Fe-Y...     

A Comparative Study of Mechanical Properties,Thermal Conductivity,Residual Stresses,and Wear Resistance of Aluminum-Alumina Composites Obtained by Squeeze Casting and Powder Metallurgy

Squeeze casting and powder metallurgy techniques were employed to fabricate AlSi12/Al₂O₃ composites, which are lightweight structural materials with potential applications in the automotive industry. The impact of the processing route on the material properties was studied. Comparative analyses were conducted for the Vickers hardness, flexural strength, fracture toughness, thermal conductivity, thermal residual stresses, and frictional wear. Our results show that the squeeze cast composite exhibits superior properties to those obtained using powder metallurgy.

     

Tumor-specific pyruvate kinase isoenzyme M2 involved in biochemical strategy of energy generation in neoplastic cells

The first observation that in vitro fertilization (IVF) was useful for treating oligozoospermia and oligoasthenozoospermia was reported by Fishel and Edwards in 1982. This was followed by a series of cases indicating the value of IVF in such cases. Conventional IVF has been modified and refined to achieve increased rates of conception in cases of male factor infertility. Methods such as high insemination concentration IVF for the treatment of teratozoospermia and microscopic IVF for the treatment of oligozoospermia have had some impact on fertilization and pregnancy rates; however, reports of success are varied. The recent advent of micromanipulation and, in particular, intracytoplasmic sperm injection (ICSI) has overshadowed the use of these modified IVF procedures. Because of the high fertilization and pregnancy rates achieved with ICSI, other micromanipulation techniques (subzonal insemination and partial zona dissection) have been abandoned; there have also been suggestions that other more conventional techniques, i.e. IVF, should also be abandoned and that ICSI become the sole technique for the treatment of infertility. The rapid increase in the number of centres using ICSI has led to extreme pressure for individual units to achieve high fertilization and pregnancy rates and there is a temptation to assign all patients to ICSI treatment. It is important that, in this highly competitive environment, new techniques are not applied haphazardly and reduced to the mere injection of gametes and achievement of pregnancy regardless of the cause of infertility. In his 1986 IVF--Historical Perspective, Fishel quoted Auguste Comte: 'to understand science it is necessary to know its history'. IVF has much recent history in animal and also human work. Although ICSI is the most significant therapeutic advance in male infertility treatment, its application to human IVF is only 4 years old, with a paucity of animal studies on which to rely. For this reason IVF still plays a very important role in the treatment of male factor infertility and should only be ruled out when it has failed previously or the number of available sperm is limited.     

Bestimmung des Grenzumformgrades mit dem Torsionsversuch

Die Bestimmung des Grenzumformgrades eines Stahles, der während der plastischen Verformung nicht überschritten werden kann, ist von großer Bedeutung. Die vorliegende Arbeit berichtet über Ergebnisse von Warmtorsionsversuchen, aus denen der Grenzumformgrad als Funktion von Temperatur und Umformgeschwindigkeit ermittelt wurde. Die Versuche wurden an den Stählen X 10 CrNiTi 18 9, 10 CrMo 9 10, X 10 CrNiMoTi 18 12, X 20 CrMoV 12 1 und X 2 NiCrNb 25 18 durchgeführt.     

Non-steroidal anti-inflammatory drugs and the protective activity of valproate and diphenylhydantoin against maximal electroshock-induced seizures in mice--an interaction

OBJECTIVE: To discuss the clinical implications of systemic lupus erythematosus (SLE) as a complication of a urological condition. METHODS: Herein we describe a patient who presented with acute pyelonephritis due to ureteropelvic juntion stenosis, and a superimposed activation of SLE that had not been previously detected. RESULTS: This form of presentation led to a delay in making the diagnosis since it was focused urologically. The diagnosis of SLE was based on the clinical features, determination of antinuclear antibodies (ANA) and a decrease in serum complement. CONCLUSION: When a patient consults with fever arising from a urological condition that is refractory to conventional therapy, it is mandatory to make the differential diagnosis from other disease entities, as shown in this case.     

The significance of beta 2-microglobulin in diagnosis and therapy

This article describes the significance of beta 2-microglobulin (beta 2m) determination both in urine and serum for the estimation of proximal renal tubular function and glomerular filtration rate. The usefulness of beta 2m in therapy, cancer diagnosing, epidemiologic investigations of industrial exposure to cadmium, lead, mercury and in evaluating etiologic factors of environmental nephropathies was also discussed.