The influence of the coordinate reduction on the identification of the joint dynamic properties

A problem of establishing a theoretical model of a joint from the measured frequency-response function (FRF) data is discussed in this paper. The model of the joint is considered as a coupled dynamic stiffness matrix, which generally includes six degrees of freedom (DoFs). For two types of least-squares solution the terms of use are clarified. The effect of coordinate reduction on the identification results is demonstrated numerically. Also the effect of added noise is studied. Using a substructure synthesis method and the identified joint dynamic properties the assembly response is reconstructed.     

Basic Properties of the Projective Product with Application to Products of Column-Allowable Nonnegative Matrices

We use basic properties of the projective product to obtain exponential bounds for the Lipschitz constant associated with the projective product of column-allowable nonnegative matrices. We obtain similar bounds for the associated linear tangent maps. Date received: May 14, 1998. Date revised: November 18, 1999.     

Distribution of the carbide phase in the viscoplastic layer during the rotational friction-welding of various steels

The paper presents the viscoplastic phenomena observed during the rotational friction-welding process of high-speed steel M2 (AISI SAE) with carbon steel 1060 (AISI SAE). The structure, phase composition and distribution of the carbide phase in the friction plane and adjoining zones are examined by using optical microscopy (OM) with a system for quantitative analysis, and scanning electron microscopy (SEM) in addition to EDS analysis. The experimentally-checked mathematical relationship is suggested for the calculation of the radial movements of the carbide phase, immediately next to the friction plane. On the basis of qualitative and quantitative evaluation of the microstructural and rheological appearances, a model of carbide phase distribution is also established in the viscoplastic and viscous layers in the area of the friction plane.     

Optimization of geometry for lateral buckling process of a cantilever beam in the elastic region

Using the large displacement theory (theory of the third order according to Chwalla), the paper deals with lateral buckling process of a slender, elastic cantilever beam with a changeable cross-sectional area and represents it with a system of nonlinear differential equations. Based on a mathematical model of the lateral buckling process which considers the geometric and boundary conditions, an optimal geometry of a cantilever beam is obtained using the calculus of variation. A comparison between the properties of the beam with optimized geometry and those of a referential beam with a constant cross section is shown. The main feature of the optimized geometry beam is a constant maximal reference stress, obtained by the deformation energy theory, along the whole length of the beam in a deflected form which means that in terms of stability the material is completely exploited. The result of this feature is, besides higher critical load, also higher carrying capacity of the optimal geometry beam in the postbuckling region.     

Vitamin C and plasma triglycerides in experimental animals and in humans

A chronic latent vitamin C deficiency in guinea pigs enhances triglyceride concentration in blood plasma but does not markedly alter the composition of fatty acids in serum and hepatal triglycerides. An addition of 0·5% ascorbic acid to the diet of golden hamsters tends to normalise alimentary hypertriglyceridemia provoked by a high-glucose fat-free diet not containing vitamin C. A daily administration of 2 × 500 mg of an effervescent ascorbic acid for three months to subjects aged between 50 and 75 who were in a state of a seasonal vitamin C deficiency resulted in a significant depression of triglyceridemia. The hypotriglyceridemic effect of ascorbic acid depended on the starting plasma concentration of triglycerides: the higher the initial triglyceridemia, the more striking the hypotriglyceridemic effect. An administration of 2 × 500 mg of effervescent ascorbic acid every 24 h to a selected group of subjects with an initial triglyceridemia above 200 mg % for the duration of one year brought about a very significant decline of triglyceridemia, and this still persisted six weeks following cessation of ascorbic acid administration. An intervention of vitamin C at the level of triglyceride splitting enzymes is presumed.     

Determination of transient two-dimensional heat transfer in ventilated lightweight low sloped roof using Fourier series

In this paper, the analysis of transient two-dimensional (2D) heat transfer in low sloped roof with forced ventilated cavity made from lightweight building elements (LBE) is presented. For the heat transfer analysis the 2D numerical model, which was verified with experiments, was used. Forced ventilated cavity was configured in two different ways. In the first case the cavity was configured with coloured thin metal sheet and in the second case with thin metal sheet with added layer of thermal insulation and radiation barrier. Beside the influence of the ventilated cavity configuration on the transient 2D heat transfer in the LBE and on the cavity outlet air temperature also the influence of the LBE thickness, specific air flow rate through the cavity, inner air temperature and wind velocity was analysed. Multi-parametric equations for determination of Fourier series coefficients were formed. These coefficients were used for evaluation of transient 2D heat transfer on the inner side of the roof and cavity outlet air temperature for a clear day.     

Production of aluminium killed steels with high sulphur contents for automotive industry

The influence of aluminium deoxidation and various amounts of injected CaSi on resulphurized steel has been investigated. The type of inclusion formed depends on the aluminium, silicium, calcium and sulphur contents. The chemical composition of the oxide inclusion was in good agreement with the prediction of the thermodynamical equilibrium calculation.     

Interactions of polarons in poly(3-dodecythiophene) at low temperature

Zero-field cooled-field-cooled (ZFC-FC) technique was used to investigate the effect of low temperature (4.6 K) on the interactions of polarons in weakly FeCl₃-doped poly(3-dodecylthiophene (PDDT). It was found that the magnetic properties of the system changed with the length of time system spent at low temperature: the Currie–Weiss paramagnetism gradually changed over to “antiferromagnetism” and ultimately to diamagnetism. This effect is connected with the thermochromic properties of self-organized PDDT in primary (10–15 nm) or secondary (30–50 nm) induced aggregates, in which cooling under the glass transition temperature T_g (～240 K) causes extension of the effective conjugation length of coplanar polymer chains. Changes in magnetic properties are related to the inter- and intra-chain interactions of polaron states within both the primary and secondary induced aggregates.     

Quantum complementarity and logical indeterminacy

Whenever a mathematical proposition to be proved requires more information than it is contained in an axiomatic system, it can neither be proved nor disproved, i.e. it is undecidable, or logically undetermined, within this axiomatic system. I will show that certain mathematical propositions on a d-valent function of a binary argument can be encoded in d-dimensional quantum states of mutually unbiased basis (MUB) sets, and truth values of the propositions can be tested in MUB measurements. I will then show that a proposition is undecidable within the system of axioms encoded in the state, if and only if the measurement associated with the proposition gives completely random outcomes.