Reliability Computation of Heat-power Engine Structures Based on Finite Element Modeling

The computational method was suggested for reliability of heat-power engine structures under continuous random in-process loads. The method is based on numerical statistical modeling of an in-process stress-strain state (SSS) of a structure with random characteristics of structural materials and computation of damage accumulation and durability of the structure under random stationary loadings. The chemical criterion of durable strength has been applied to calculate damage accumulation. The iteration method for a three-dimensional thermo-mechanics problem and the finite-element method have been used to compute the SSS of structures regarding creep. As an example of application of the developed method, computations for durability and reliability of two-layer cooled structure of a thermo-energetic power plant case have been conducted.

On the possible formation of Aurivillius phases in the oxide system Bi2O3-ZnO-Nb2O5

This paper presents results concerning the possible synthesis of double perovskite and Aurivillius phases in the BZN system. Acrystal chemical criterion based on an elastic model for the structure was used in order to determine if the formation of layered bismuth compounds is favoured in the above system. The tempeature seems to be the decisive factor influencing Aurivillius phase formation.

Assessing emission reduction targets with dynamic models: deriving target load functions for use in integrated assessment

International agreements to reduce the emission of acidifying sulphur (S) and nitrogen (N) compounds have been negotiated on the basis of an understanding of the link between acidification related changes in soil and surface water chemistry and terrestrial and aquatic biota. The quantification of this link is incorporated within the concept of critical loads. Critical loads are calculated using steady state models and give no indication of the time within which acidified ecosystems might be expected to recover. Dynamic models provide an opportunity to assess the timescale of recovery and can go further to provide outputs which can be used in future emission reduction strategies. In this respect, the Target Load Function (TLF) is proposed as a means of assessing the deposition load necessary to restore a damaged ecosystem to some pre-defined acceptable state by a certain time in the future. A target load represents the deposition of S and N in a defined year (implementation year) for which the critical limit is achieved in a defined time (target year). A TLF is constructed using an appropriate dynamic model to determine the value of a chemical criterion at a given point in time given a temporal pattern of S and N deposition loads. A TLF requires information regarding: (i) the chemical criterion required to protect the chosen biological receptor (i.e. the critical limit); (ii) the year in which the critical limit is required to be achieved; and (iii) time pattern of future emission reductions. In addition, the TLF can be assessed for whole regions to incorporate the effect of these three essentially ecosystem management decisions. Keywords: emission reduction, critical load, target load, dynamic model, recovery time

A New Chemical Criterion for the Quality Control of Fish: Trimethylamine/Total Volatile Basic Nitrogen (%)

Trimethylamine (TMA) and the total volatile basic nitrogen (TVBN) were determined in 169 samples of sea-fish (herring, cod, whiting, and mackerel) at all stages of decomposition. The comparison of these two parameters with the ratio P=TVBN/TMA (%) showed that P provides a useful index of freshness. It is relatively constant between species, its dispersion is less than that of TMA and it increases more rapidly than TVBN at the start of decomposition. Statistical analysis of the experimental results showed that there is a non-linear correlation between P and the decomposition index (i). The comparison of the line-equations defining log P as a function of i for different species of marine Teleostei led us to show that there is little or no intraspace variation of this correlation under determined conservation conditions. It is noted that for a given species, this correlation is temperature-dependant. Statistical exploitation of these results permit us to determine the maximal admissible values for P which can be used as a support for the development of new standards.