Vol 14, No 3 (2014)

Mathematical models of aircraft maintenance are discussed in the paper. The first model is that of aircraft downtime, which is a function of the number of periodically performed technical operations. The second model is that of optimal maintenance periodicity to support airworthiness in conditions of providing a given level of aircraft reliability. The third model is an optimization model of aircraft maintenance costs and providing maximum profit in market economy conditions. Using the theory of differential equations as well as the theories of reliability and renewal formulae of calculating optimal allotted aircraft downtime during periodic technical operations aimed at supporting the airworthiness as well as the formulae of optimal maintenance periodicity, optimal number of maintenance operations and getting maximum profits from flight operations have been found. The proposed models are investigated with a view to specifying acceptable maintenance periodicity with regard for the cost-benefit ratio of aircraft maintenance and the possibility of using them to optimize the maintenance of the ageing fleet of civil aviation. The calculations made show the necessity of decreasing maintenance periodicity in order to optimize the servicing and efficient use of the aircraft ageing fleet.

The paper presents the experience gained by the “Saturn” science-and-production association in producing a bifuel combustion chamber for the E70/8RD engine. The data on the modernization of the combustion chamber based on the RQQL (rich /quick quench/poor combustion) technology that made it possible to reduce significantly the emissions of NOx while working on natural gas and to meet the requirements of the technical project of the engine are presented. The problem of providing the thermal state of the flame tube walls is also discussed.

The paper deals with longitudinal elastic-plastic impact on a two-layer composite rod with a fixed opposite end. The composite   rod consists of a soft layer (aluminum) and a hard layer (steel), with their position varying. The condition of the continuity of the particle velocity vector and the stress is met on the contact boundary of the rods. To describe the wave processes the grid-characteristic method is used which makes it possible to construct computational algorithms on the borders of the integration area and the interfaces correctly. The interaction of reflected and refracted stress waves at the interface of composite rods is analyzed.. The phenomena on the interface of composite rods are made more complicated by their interaction with the dynamics of changing both the applied external load and the stress waves reflected from the boundary surfaces. As a result of numerical studies we have shown the possibility of damages on the interface for an aluminum-steel composite rod and rapid decay of non-linear effects in the case of steel-aluminum. Positioning rods with specific mechanical characteristics in the order specified by the calculations, we found a possibility to control the level of dynamic loading of each individual element of the composite rod, and hence the operability of the whole composite rod.

The paper presents the results of work involving chemical vapor plating of an organometalic compound of aluminum coatings on a high-strength steel backplate using a catalytical additive. The process of coating deposition is carried out in a sealed chamber with subsequent capture of decomposition products in a nitrogen trap, which provides environmental safety of the process. The paper describes the choice of a catalytical additive among the following liquids: titanium sec-butoxide, titanium tetrachloride, three-n-propylamine used to reduce the deposition temperature. It was found that the deposition of pyrolysis-induced aluminum coatings using catalytical additives does not change the mechanical properties of high-strength steel. Corrosion tests have shown that the protective properties of samples with pyrolysis-induced aluminum coatings are superior to those of zinc coatings.

The causes of black spot defects detected on the surface of large parts made of aluminum alloys (D16chT, 1973T2, V95pchT2, V95pchT3) following anodic oxidation   are investigated in the paper. A hypothesis of such defects appearing during the dissolution of intermetallics on the surface of a part in the process of etching during anodizing was put forward and tested. A technique was developed for this purpose the essence of which was that an intermetallic was detected on a polished sample and using a microhardness tester the area including the intermetallic was marked to facilitate its subsequent detection at the end of the specimen etching. After the etching of the specimen during periods of different duration in an alkaline bath of the anodizing line the area containing an intermetallic previously labeled using the microhardness tester was detected by microscopic observations and photographed. The duration of the etching process was 120 seconds and consisted of 8 cycles. Metallographic tests of the specimens. revealed the fact that in the process of etching of an aluminum alloy dissolution (etching) of intermetallic particles opening out on the surface of the part takes place. Subsequent anodic oxidation leads to the visualization of defects which have the form of black spots.

The article is concerned with the consideration of methods of mathematical formulation of processes in interthrottle chambers and working medium reservoirs used to simulate the operation of hydraulic and pneumatic systems.

Consideration has been given to a general approach to the development of mathematical models of hydraulic and pneumatic systems; the stages of constructing models are also presented.

A generalized mathematical model of a heat-insulated chamber with variable volume is presented. The derivation of standard mathematical modules of the above chamber on the basis of the generalized model is given. The assumptions taken into consideration with the existing methods of describing the processes taking place in chambers and reservoirs of hydraulic and pneumatic systems are analyzed. The shortcomings of the existing methods are shown.

An approach to forming a mathematical formulation is proposed, which is universal in its nature and reflects the processes under consideration in full measure. The proposed description method is based on the laws of conservation of thermodynamics of a variable-mass body. A special record of thermal and caloric equations of the state model makes it universal and independent of the working medium type. When compiling the digital models of chambers, both equations of working medium state and tabulated reference data can be used.

 Design diagrams and mathematical models of heat-insulated chambers with variable and constant volumes are presented as an example. A digital model is presented and the results of modeling the operation of hydraulic and pneumatic actuators performed with the use of the proposed method are given. The digital model is implemented in the training version of the Russian software package “Simulation in technical devices”.

The main efforts in overcoming the diffraction limit have been recently concentrated on the use of damped waves. The implementation, however, is connected with a serious drawback: superresolution is attained only in the immediate vicinity of the device, namely, at a distance of less than the wavelength. It is, therefore, impossible to use the available results, in particular, to reduce information on optical media. The aim of the paper is calculation of optical elements for subwave focusing of a monochromatic wave at a distance of several dozens of wave lengths. The problem of overcoming the diffraction limit expressed in accordance with the Abby theory and the Raleigh criterion dealt with in multiple fundamental and applied investigations is discussed in the paper. The analysis of subwavelength localization of radiation based on the interference effect that makes it possible to reduce the sizes of a light spot due to redistribution of energy in the peripheral area holds a prominent place in the paper. Calculations are performed using the iterative algorithm based on the method of plane wave expansion and the method of main directions. The problem is considered for the cylindrical and radial cases. Special attention is given to the search of solutions that would be more convenient for practical implementation. Prospective viability of developing the solution of the problem for data storage, contactless probing and nanolithography is demonstrated.

The paper is devoted to the simulation of ultrashort pulse propagation in waveguides of two types. The first type (type 1) represents an ordinary waveguide made of cylindrically shaped fused silica without coating. The second type (type 2) consists of microspheres made of the same fused silica following one another. A three-parameter Sellmeyer model is used to take into account the dependence of electrical permittivity on the frequency of radiation. The coefficients of pulse broadening and amplification as well as the coefficient of the pulse spectrum narrowing have been calculated. The numerical simulation using the FDTD method which takes into account the frequency dependence of the permittivity and implemented in the FullWAVE software package  showed that there is no temporal broadening in the case of  propagation of linearly polarized ultrashort pulse  3.55 fs long with a central wavelength of 532 nm in a waveguide consisting of a sequence of fused silica microspheres with the radius of 1 mkm, while there is a two-fold temporal broadening of the  pulse  in the case of transmission of this pulse in a conventional silica cylindrical waveguide.

The main task of ontology description languages is to describe semantics of domain data. Nowadays, ontology is the most common form of representation of semantically-interconnected data. Ontology consists of a set of concepts in a domain and relations between them. In this paper we consider the problems of existing toolkits for creating semantically-interconnected data storages for engineering domains and propose a solution in the form of an ontology. A modern approach to the classification of assets for ontology engineering is presented. The strengths and weaknesses of the approaches described are highlighted. The paper describes problems of structuring data in the engineering domain and the ways they can be solved using ontologies. A brief review of the common ontology description languages is given. Examples of the applied ontological approach in the database creation in the airspace engineering domain are presented. XML and HTML are highlighted as the most widespread languages in the description of subject areas in modern information systems. The OWL ontology description language is described in detail as the most promising ontology description language recommended by the W3C. Varieties of the OWL language are described in terms of their applicability to solving various problems of describing engineering domains taking into account the limitations of descriptive ability and complexity of the syntax of each version. Examples of the use of the OWL language in engineering domains are given.

The paper deals with the semantic roots of such concepts as «innovation», «innovation process», «innovative product»; reasons are given for the necessity of looking for criteria of distinguishing innovations from pseudoinnovations. The author’s version of defining the above-mentioned concepts from the perspective of the theory of the subject of labour is presented. The «innovation» concept can be used in cases when consumer-cost and cost process chains are designed with regard for technical and technological, economic, social and ecological components both at the level of tactical aims (obtaining a product with a parameter required by the society) and at the level of strategic aims (obtaining a product the production of which causes minimum damage to the biosphere). The «innovation process» concept can be used referring to life cycles in which, starting from the product of nature (the object of research), through intermediate stages at which the technological waste is utilized to the product of nature when the final industrial and household products out of use are added to the biogeochemical Earth cycles. The «innovative product» concept can be used to denote the final products of material production that find practical application in the achievement of the required technical and technological, economic, social and ecological effects and taking measures to utilize the by-products during the life cycle and at the final stage through the connection of the ballast substrate to the biogeochemical Earth cycles.