Methods and tutorials
Purpose: to analyze the features of training of bachelors and masters in advertising sphere and public relations for aerospace field. The article deals with the specifics of bachelors training at «Advertising and Public Relations in aerospace field» and with the specifics of masters at «Public Relations in aviation sphere» in Moscow Aviation Institute (National Research University). The article analyzes the features of the interpenetration of classroom teaching, practical training and scientific research work of students. It is shown in the article that practice and research work are closely connected with theoretical training, there must be integration of scientific and practice disciplines, theoretical knowledge must be supported by practice skills.
The authors consider the features of contents of training programs for student’s practice and scientific research work of different studying forms, taking into account the modern requests of advertising and public relations sphere and interests of employers that are representatives of aerospace field. The authors think that the estimation criteria of efficiency of graduates are awards from special contests and future professional career of graduates.
Conclusions of the study are applicable to the training of bachelors and masters, studying at «Advertising and public relations» in different institutions of higher education, and for training of graduates, taking into account the specifics of different spheres.
Keywords: public relations, advertisement, scientific research work, educational training program, training orientation, aerospace field, aviation sphere
The conceptual foundations of professional foreign language communicative competence in teaching of foreign languages at the aviation technical University students, can be achieved through the development of skills and knowledg of the course of professional interaction in a foreign language. The most important structural components in the formation of professional foreign language communicative competence of students of the aviation University are: motivational and value, informative and behavioral-activity components. With the help of the foreign student’s communicative competence in Aviation Technical University, you can plan the students efforts, deliberately apply psycho-pedagogical methods and anticipate, predict the results. Organizational-MOTIVATIONAL COMPONENT-system of values-people, professionals, communication, cognition, motivation, orientation, evaluation of experience
MEANINGFUL procedure is the system of knowledge, skills and foreign language skills to master the aeronautical knowledge, mastering the communicative activities, communication equipment, professionally-relevant communication qualities.
EFFICIENTLY-CRITERIALNY COMPONENT-stepwise level monitoring of foreign students ’ communicative competence, professional analysis, correction. Organizational and motivational aspect of preparing students for forming of communicative skills is implemented under certain conditions:
1. Focus study of scientific literature, learning a foreign language to communicate, as one of the main educational values.
2. The activity of the students when discussing professional work.
3. Encouraging the active communication between students and teachers, with each other, a foreign language classes.
4. Organization of research, research work on professional activities in a foreign language class as part of the contextual approach. Meaningful procedure component. Knowledge of communicative activity updates the communicative behavior:
1. Knowledge of the role and place of communicative skills within the professional competence of the expert.
2. Knowledge of the entity and the main components of professional foreign language communicative activities.
3. Knowledge of the patterns of foreign professional communication skills specialist of aviation profile.
4. Knowledge of algorithms of behaviour in situations of communication, tactics, and strategy.
5. Knowledge of the tools, forms, methods of information transfer in the process of communication.
6. Knowledge of different kinds of communicative activity. Meaningful procedure component is implemented by means of language learning based on the scientific literature. (6)
7. Communicative skills are implemented by mastering the communicative techniques and technology.
Keywords: the structure of professional foreign language communicative competence, self-concept, student of aviation university, organizational, motivational, informative, behavioral-activity, axiological, gnoseologicheskay
The current situation in the Russian and international job markets — with their business internationalization challenges — requires certain revision of both the content and methods of tertiary non-linguistic education. Thus, there is the progressing issue of the development of what the author termed to be ‘the professional intercultural strategic competency of non-linguistic students’ (PISCoNoLiS) which is scrutinized in the present paper.
The research work was based on a sequence of research questions:
1. What are the rationale and the research background of PISCoNoLiS?
2. What should be the components of PISCoNoLiS?
3. What should be the efficient methods, environments and resources for the development of PISCoNoLiS?
The research is backgrounded a number the previous research projects and the relevant publications of Russian and international academics in the theory and practice of intercultural communication (Deniels, Herskovits, Hofstede, Faerch, Kasper, Kluckhohn, Kostomarov, Leont’ev, etc.), the paradigm of the competency approach in education (Zimniya, Kuznetsov, etc.), intercultural training (Alipichev, Herskovits, Kostomarov, Kuznetsov, etc.), scripting for didactic purposes (Lim, Kuznetsov, Popov, Rummel, Weinberger, etc.).
Among the principle research methods of the present study there were the following: the SWOT analysis of the intercultural communication in the professional field, the SWOT analysis of intercultural training, expert evaluation, trial teaching, student sampling and dyading, contrasting and comparing of speech patterns across languages, material sampling, and the content analysis of the training manuals.
The professional intercultural strategic competency of non-linguistic students has been researched in the context of the emerging novel requirements of the present-day job market, the paradigm of the competency approach in education, reality of the Russian and international education, and the outcomes of the previous research in the field. The author presents the rationale and the theoretical background of PISCoNoLiS research, its components, as well as the most efficient methods, environments and resources for the development of PISCoNoLiS. Special focus is being given to the development of the PISCoNoLiS relevant training methodology and tools (strategy layout, a series of manuals, multimedia training kit, etc). Though, further research in the field the development of PISCoNoLiS has proved to be required.
Keywords: intercultural communication, professional communication, scripting, scaffolding, technical universities
The article deals with the problem of teaching lexical competence and terminology at the Aviation University. The ultimate goal of the foreign language course in non-linguistic universities is the development of intercultural communicative competence. Professionally oriented new standards are not provided with textbooks and teaching aids, which would be fully consistent with the aims and objectives of learning a foreign language in aviation universities. Professional aviation terminology is studied while improving lexical skills of the linguistic competence, i.e. the ability to adequately and correctly use and understand speech patterns based on the knowledge of phonological, grammatical, lexical, stylistic features of the target language (in comparison with the native language).
The topics for the English lessons are selected according to the major specialty courses of the university, for example, the history of flights, the outstanding people in the aviation and space, the basic concepts in the field of aviation. Experience shows, some special aviation terminology is acquired in the English lessons during the first year of studying in the University. To select the minimum terminology comparative analysis of bilingual and monolingual aviation dictionaries with General vocabulary dictionaries is required. The main method of term formation is considered to be syntactic, i.e. formation of terms in a chain. For example, multicomponent combinations predominate in English technical terminology and they cause difficulties in translation.
The typology of lexical exercises to overcome these difficulties includes the following ones: continue the word family table; match each of the expressions on the left with their explanation from the list on the right; fill in the word family table; make the diagram of the text using the key words from the text. For the exercises to be effective they should be designed to blend with the terms studied during the earlier lessons.
Keywords: Aviation English, aviation terminology, lexical skills, exercises
Mathematics. Physics. Mechanics
The article is devoted to solving problem of stochastic system position correction by quantile criterion. The single-pulse correction case is considered in the article. It is required to determine the correction pulse which will provide system movement from one position to another in minimal time. This problem can be written as a two-stage stochastic programming problem. The strategy is determined on the first stage, and different random factors (interference) appear with the realization of the first stage strategy. The impact of random factors is partially compensated by the choice of the new strategy (the second stage strategy). Traditionally, the expectation value (average loss) is considered as the problem criterion in the two-stage stochastic programming problems. But the control accuracy which is guaranteed with a given probability is more appropriate criterion in the aircraft control problems. Mathematically, this criterion is described with the quantile function.
The two-stage stochastic programming problem with the normal distribution of the random factors is considered in the article. The feature of the problem statement is the kind of the loss function, namely its linearity both random factors and strategies. Thus the loss function is the bilinear function. It is assumed that the random factors have the normal distribution. But the class of the random factors distribution can be expanded. For example, the random factors may have the spherically symmetrical distribution. In this case only size of the confidence sphere and the kernel of probability measure are changes.
An algorithm to obtain a guarantees solutions is proposed in this article. This algorithm based on the confidence method and reducing the initial problem to the convex programming problem which is parameterized by a scalar parameter. This parameter is determined in the algorithm by dichotomy. The counting procedure of the polyhedral set probability measure is the main complexity of the proposed algorithm. The discretization of the normal distribution and a process of reducing the search of points are offered for the time decreased.
Keywords: stochastic programming, two-stage problem, quantile criterion, normal distribution, convex programming
The evaluation problems for the probabilistic and quantile criteria arise when estimating the terminal precision of the aircraft control under the random disturbances. The probabilistic criterion reflects usually the probability of attaining a control goal and the quantile one is a making decision result (the control precision) guaranteed with a given probability. The known evaluation techniques for these criteria are iterative numerical procedures having no stopping rules. For this reason they cannot allow us to obtain a result with the given precision. The paper presents more exact techniques for evaluating the cumulative distribution function and quantiles of the random variable which is piece-wise linear with respect to the Gaussian random vector.
The quantile evaluation problem is reduced to searching a root of equation for the cumulative distribution function. Such an equation can be solved with the given precision if the cumulative distribution function is approximated exactly by its two-sided bounds. The bounds are constructed by lower and upper approximations for the probability that the Gaussian vector belongs to the compact convex polyhedron.
The bounds on the probability are generated by special numerical integration procedures for the Gaussian probability density function over the compact convex polyhedron.
The efficiency of the presented techniques is demonstrated by a two-dimensional example.
The evaluation techniques are implemented as a software.
Keywords: probability, the quantile, linear inequalities, convex polyhedrons
Construct an approximate solution of the Liouville problem about free rotational motion of an isolated celestial body with weakly variable geometry of mass, based on the equations of motion in action — angle variables for the Euler — Poinsot problem.
In this paper the new form of the equations of rotational motion of a celestial body in the action-angle variables for the Euler-Poinsot problem have been obtained. This allowed effectively applied the small parameter method and derive analytical formulas for the perturbations of action-angle variables of the first order. An important role herewith were played by the Fourier series for the first degrees, squares and mixed product of the direction cosines of the axes of inertia of the body in the basic coordinate system.
Perturbation theory of rotational motion of a celestial body contains effects that have not been described previously. And unperturbed motion accepted as free motion of a rigid body by Euler-Poinsot law, whose parameters can be arbitrary (any polhode except separatrices). As a consequence of this generalization (for triaxial planet) a description of amplitudes perturbations and spectrum perturbations is given by using the apparatus of elliptic functions and elliptic integrals.
The obtained results represent an important interest for research in celestial mechanics and geodynamics. They allow identify new effects in pole motion and in the diurnal rotation of the planets and asteroids. So the formulas for the first-order perturbation contain variations with new periods (compared to perturbations, obtained by classical method based on the Euler-Liouville equations).
Researchers studying perturbed rotational motions of the celestial bodies, have received new opportunities with using equations of motion, constructed in action -angle variables. The developed approach allows the direct use of data of space geodesy about variations of the Earth’s mass geometry directly from the observed variations of the geopotential coefficients. Thereby methods of space geodesy and study methods of perturbed motions of the Earth’s pole and variations of its axial rotation, act here like a single tandem and allow obtaining new results. Primarily, these results are of interest to study the effect of redistribution of mass of celestial bodies on movement of their poles and on their diurnal axial rotation. Obtained form of the equations of Liouville problem in action-angle variables, will be widely used in subsequent studies.
The results of this paper can be used in the basic and special courses of lectures for undergraduate and postgraduate students in the departments of theoretical mechanics, theoretical astronomy and celestial mechanics, etc.
Keywords: action-angle variables, the unperturbed motion Euler – Poinsot problem, Liouville problem, Fourier series, elliptic integral
This paper presents the problem of the control of plane motions of a two-mass pendulum (swing). The swing is modeled as a weightless rod with two points of mass. The one end of the rod is hinged to a fixed point and can perform rotational or oscillatory motions in a vertical plane around the pivot. The first mass is fixed on the rod, and the second one is bound to slide along the rod. The swing moves in a uniform gravitational field. The two-mass pendulum has two equilibrium positions. The lower one is stable and upper one is instable. Friction forces are neglected.
The swing parametric control by the means of swing excitation and swing damping in the vicinity of the lower equilibrium position are discussed. The control is carried out by the continuously varying of the length from the pendulum pivot to the moving point mass. The control is a function that depends on the representative point of the moving point mass in the phase plane. The bounded and continuous derivative is required for the control.
The aim of this paper is to construct the new moving point mass control laws with a set of specified properties that implement excitation and damping swing processes near the lower equilibrium.
The problem is solved using the Lyapunov functions method of the classical stability theory.
In this paper two control laws of excitation and damping swing processes with the assumption of the restrictions on the motion of the moving point mass are constructed. The Lyapunov functions are found out that prove the asymptotic stability and instability of the pendulum lower position in cases of the pendulum damping and excitation. It is shown that the asymptotic damping oscillation amplitude swings happen for any initial conditions in case of the controlled moving point mass motion along the rod according to the first law. As for the controlling according to the second law the amplitude growth and the transition from oscillatory to rotational motions occur. The theoretical results are illustrated by the graphic demonstration of the numerical results.
The results of this paper can be used for modeling and controling of plane pendulum motions in the various mechanical systems.
Keywords: inverted pendulum, limited control, Lyapunov's function, asymptotical stability
In this paper we consider a movement of the inverted two-link pendulum on a cart system with restricted resources of perturbation. The pendulum system has two ideal motors. One of the motors is located in the node of the pendulum, and with the aid of the second motor pendulum is mounted on the cart. The control of the ideal motors is constructed as a feedback of potentiometers measurements. This provides oscillatory behavior of the system and ensures asymptotic stability of the zero equilibrium point. By means of the changing coordinates the system represents in a new form. The new system is considered under assumption of smallness of coefficients ligation and multiplicity of eigenfrequencies. The selection of the cart system acceleration as piecewise constant function of the angular velocity is based on the analysis of maximum deviation of pendulum’s center of gravity using Pontryagin`s maximum principle. The orbitally-stable limit cycle for fourth-order system has been constructed by integrating the system with selected deviation and constructing the successor function on a secant plane in four-dimensional space. Self-oscillations correspond to the limit cycle. The achievable line was founded on the secant plane. The achievable line means that in the phase space trajectories of the system that begin from this line necessarily come back to the line infinite times. Obtained system’s self-oscillations can be a maximum, i.e. limit cycle can be a boundary of the achievable set for the pendulum center of gravity. The resulting algorithm of the cart movement can be used as a test motion for the imitation stand for the vestibular prosthesis verification.
Keywords: inverted pendulum, autooscillation, limit cycle, worst disturbance, vestibular prosthesis
The article deals with the principles of rational structural design with the use of composite materials (CM) based on taking into account peculiarities of abutting joints design. There has been analyzed distribution of local stress in the area of bolt joints installation at stretching and compressing (crushing) of CM. It is shown that magnitude of crushing compressive stresses which cause splitting (gauging) of CM threads in the areas where CM mate the adjacent structure is significantly larger than that of stresses in the regular CM area. Such stresses appear in the areas of fittings installation at loading the structure made of CM and typically mean the beginning of structural damage. There has been formulated a principle of weight efficiency being primarily affected by the use of CM in structures of abutting joints mass.
There has been substantiated the choice of technology of CM structures production which meets the requirements of structural and force diagram of an aircraft unit. The article contains examples of applying the traditional autoclave technology of CM structures production and the perspective PTM technology of designing the typical construction of high-lift devices unit of an aircraft. It is shown how application of technology which does not correspond to the given structural and force diagram (SFD) of a unit affects structural rigidity and strength. There has been formulated a principle of mandatory correspondence of the SFD of a given unit and the capabilities of the CM structure production method being used.
There has been shown complexity of matching tolerances of butted metal parts and CM parts. For example, coupling sizes and surfaces of load-carrying supports used for attaching a CM part to the adjacent structure usually have tolerances which correspond to mechanically processed surfaces, while surfaces of CM parts correspond to free dimensions which are the result of polymerization. There has been formulated a principle of mandatory compliance of tolerances for coupling sizes of parts being butted based on constructional capabilities of a metal structure and technological peculiarities of CM production.
Keywords: composite material, rational design, technology, unit
The main purpose of the article was the investigation of aerodynamic characteristics of the aircraft wings which have a small span and large solid length along the body. Given characteristics make necessary to develop a new methodology for calculation of the aircraft aerodynamic coefficients.
There was a performed experimental measurement of aerodynamic forces and pitch moments of aircraft models. The experiments were conducted in a wind laboratory of the Moscow Aviation Institute. The experimental results are presented in the form of graphs. The value of the coefficients depends on wings shape, Mach numbers and angles of attack
It was found that the normal force coefficients depend primarily on the wing area. They do not depend on the shape and length of the leading edge of the wing along the airframe. If the coefficients of normal force attribute to the projected area of the wings and body to the wing area, then all aircraft at the same Mach numbers have the same dependence between these coefficients and angle of attack.
It was found that the relative position of the pressure centers of the normal forces of wings with different configurations, expressed as a fraction of the wing chord, depends only on the value of the chord. It does not depend on the shape of the leading edge of the wings and their length along the body. This observation also underlies the coefficients calculation method of the pitching moment.
Studies are limited in Mach numbers from 0.64 to 1.44. The ratio between housing diameter and wing span is limited by 0.16. Some research has been carried out for the flow velocity 47 m/s in the wind tunnel. This limits the range of the calculated value with Mach less than 3. When the diameter of a scale in calculation greater than 0.16 the developed method will be accumulated.
The developed method allows to determine the coefficients of the normal force and pitching moment in very complex layouts aircraft. Other methods do not permit this.
A new engineering method for calculation of the aerodynamic coefficients of forces and longitudinal moment of aircraft is developed. The aircraft has the small X-wings aspect ratio. They fit into a square with sides equal to the diameter casing and they have a bigger extension along the fuselage. Method is simple and accurate enough. Results of calculation are compared with the aerodynamic experimental data. The experiment is conducted by using the wind tunnel of the department for aerodynamics of the Moscow Aviation Institute (National Research University).
Keywords: calculation method, aerodynamic coefficients, the aircraft, the scheme "X", the body, wings, low elongation, small scale, experiment
The subject of the article is the development of geometrical models and algorithms of computer-aided design of the connecting tracks which are comparable to the extent of already placed objects (so-called physical trace) with their sizes. The additional requirements of routing design of trace are restrictions of smoothness to the flow lines of the track.
As the solution of this requirement, we will use the discrete method (receptor model) based on a grid which can simulate the basic designs of the tracks in layout space. Such models are used for trace of multilayered printed-circuit boards; but the direct use of these well-known algorithms to solve the problem formulated above is impossible because the smoothness (the given set of radius of curvature) of the track and safe distance between the obstacles objects and the track are not secured.
We have modified the most perfect algorithms for discrete path finding, the Dijkstra’s and A* (AStar) algorithms. The base principle of these algorithms is close to the methodology of the receptor geometrical models, and their great advantage is the simplicity of obstacle determination via receptor code (0 or 1). We have to eliminate the defect of known algorithms such as the ignoring of the obstacles before collision on them.
The main modifications of the known algorithms are the heuristic optimization of the algorithm which determines the choice of the search direction to target, so that allows one the avoiding of the bypass of many extra vertices. Another modification is the choice of the search direction as defined by heuristic methods. Usually path finding algorithms use 4- or 8-directions method which can determine how the next child node will be selected from parent node (for 2D and 3D models respectively). In our 3D multi-directional algorithm we use 26 adjacent vertices to find a way to destinations. So this method can be 300-1200 times faster the path finding process compared with known algorithms.
Using a receptor method as geometrical modeling for finding track has both the advantages and the disadvantages. The advantage of receptor model is the unique simplicity of determination of mutual non-intersection condition of already placed objects. The disadvantage is the impossibility of creation of objects with high order of smoothness. Therefore we need to make modifications to exiting algorithms for most effective routing track as offered method. Example of its implementation is designing of canal among already placed objects. In this article, we use our method for possible layout design of air intake hose among existing configuration of a motor compartment of ASA-2 light plane.
The assessment of accuracy of the offered algorithm showed that it depends on discretization of a receptor matrix and at its size of 0,2 mm makes 0,12 mm that is quite enough for a design stage of the new track. Rapid growth of productivity of computers makes discrete receptor models more and more attractive and more and more demanded in practice of design of hi-tech equipment.
Keywords: engineering design, pathfinding, receptor models, physical trace, canal surface , avoid obstacles, smoothing trajectory, service area accuracy
This work focuses on the design of an integrated control system for engine thrust and steering actuators of an aircraft during automatic docking.
The main aim is to develop a coordinated digital controller for the terminal control of an aircraft based on linear regulator and relay elements.
Our method will address a control law designed for missions, assuming the task of guidance of an aircraft to a terminal point. From the standpoint of the variation calculus method, this law may be split to two problems: one guiding the machine to a fixed location, and another — to a movable one. The cases where a part of the terminal point’s coordinates isn’t fixed or is defined through some constraints, being mode common. The problems of landing on a runway at a given point or mooring an airship to a mast with zero final velocity are discussed in this paper.
As a result we have proposed a control system structure for high speed terminal control, comprising a logical and an executive part. The logical part contains an evaluation unit for measuring control errors of the relative longitudinal and lateral movements during the control by coordinates on lateral and longitudinal channels, and two logic analyzer, looking for coincidence of deviation signs on position and speed. The executive part contains two linear and two relay controllers, the first pair is used for careful and soft docking, and the second — for speeding up the processing of significant deviations.
This research results may apply to aircrafts or river ships.
We conclude that the resulting solution is indeed applicable to the control as airships, where a minimal approach time to a desired end point is required, and for aircrafts, landing in bad weather conditions.
Keywords: aircraft, airship, traction, steering actuator, terminal point, optimal control, linear and relay control, berthing
The accuracy analysis of the point gravity method during the design of interplanetary trajectory of the spacecraft with electric propulsion via Earth swing-by.
Development of a method for designing the interplanetary trajectories of the spacecraft with electric propulsion via Earth swing-by using restricted three-body problem for spacecraft motion.
Comparative analysis between use of the point gravity method and use of the restricted three -body problem.
The heliocentric trajectory optimization problem is formulated by using the Pontryagin’s maximum principle.
Motion equations of spacecraft are written with the help of restricted three-body problem.
The continuation method in parameter is used to solve the boundary value problem.
The originality of this article is related to the development of method for the trajectory optimization of the spacecraft with electric propulsion for the Jupiter flight via Earth swing-by in the restricted three-body problem.
The method for the interplanetary trajectory of the spacecraft with electric propulsion for the Jupiter flight via Earth swing-by in the restricted three-body problem is developed.
It is shown that the mass estimation method precision of spacecraft with electric propulsion to explore Jupiter with using Earth swing-by which is formulated on the point gravity method is not more than 1%. This is the confirmation of the correctness of the point gravity method in designing the interplanetary trajectory of the spacecraft.
The comparative analysis of the above two methods is presented.
Space mission to the Jupiter with nuclear electric propulsion.
In this paper the method of interplanetary trajectory of spacecraft with electric propulsion via Earth swing-by using models of spacecraft motion in the restricted three-body problem is proposed. In order to optimize the trajectory of spacecraft Pontryagin’s maximum principle is used. The method can be used to analyze any interplanetary trajectories with nuclear electric propulsion with gravity assist maneuver from any planet.
The comparative analysis of results for using two types of spacecraft motion model (the point gravity method and motion equations written by the restricted three-body problem) is shown. Types of trajectories and structure of switching functions using these two methods are practically coincided, and relative deviation of the required mass of xenon does not exceed one percent.
The comparative analysis has shown the correct usage of the point gravity method in designing spacecraft trajectories with electric propulsion for the Jupiter flight via Earth swing-by.
Keywords: spacecraft, Jupiter, optimal trajectory, gravity assist trajectory, transversality conditions
The spacecraft protection against the intense aerodynamic heating is one of the most important problems inprogram of outer space exploration. The main task at the design stage of creating a new spacecraft is selection and development of reliable and efficient thermal protection system. For the development of such a system is very important to calculate correctly the thermodynamic processes of gas dynamics, heat and mass transfer on the spacecraft surface. Otherwise, the system of thermal protection would be unreliable and spacecraft cannot achieve the strategic mission.
The article presents the results of the analysis of heat and mass transfer on the cold surface of the landing spacecraft, designed as a cone blunted by sphere, during it descend from a circular orbit in the dense layers of the Earth’s atmosphere along a complex hypothetical trajectory. The calculation of heattransferwas conducted using known parabolic criterion ratios. Such engineering calculation does not require knowledge of complex wave gas dynamicsof spacecraft in hypersonic flow. The gas dynamics parameters of the outer edge of the boundary layer, which are necessary for computation, were calculated using an algorithm withgas dynamics tables of supersonic flow on the surface of a cones blunted by sphere.
By using this algorithm the trajectory parameters and heat transfer on the surface of the landing spacecraft in a hypersonic flight phase with duration of more 1000secondswere calculated. The analysis of the calculation results was a basis for selection of «active» thermal protection system for warhead of landing spacecraft. The calculation of required mass flow rate of the cooling gas, which gives reliable operating conditions of the system in the area of blunting, was conducted.
Keywords: landing spacecraft, heat and mass transfer, hypersonic speed, thermal protection, trajectory parameters, stagnation enthalpy, mass flow rate of cooling gas
Aerospace propulsion engineering
Influence of interphase convective heat exchange on change of phases velocities in a two-phase turbulent jet are investigated.
As a research technique mathematical modeling is chosen. By means of mathematical model of a two-phase turbulent jet the calculations of jets with taking into account interphase heat exchange and without interphase heat exchange were made. As measure of an estimate of influence of heat exchange on change of velocity in a jet the distance from a nozzle is chosen on which velocity of gas on an axis of a jet is twice less than velocity in initial section of jet.
As a result of the calculations the quantitative data about influence of convective heat exchange between particles and gas phase on gas velocity in a two-phase jet depending on a volume concentration and the size of particles, and also temperature of phases in initial section of a jet are obtained.
When the volume concentration of particles is less than 10-4 interphase heat exchange has no influence on the change of the gas velocity in two-phase jet. The increase of initial temperature of phases leads to essential increase of an error of velocity calculations in a jet when conducting of which is not included interphase heat transfer, and this error increases with the increase of the volume concentration of particles (at initial temperature of phases 1500К and a volume concentration of particles 2×10-3 the error of definition of gas velocity could reach 200 %). Dependence of an error of gas speed calculation in a jet on the size and volume particles concentration at neglect interphase heat exchange are not monotonous — there were the maxima of this error corresponding to certain values of Stokes number and initial particles concentration.
The results can be used to develop mathematical models of two-phase jets (particularly jet of aircraft engines) in order to simplify these models.
Keywords: two-phase jet, the mathematical model, convective heat transfer, velocities of phases
Theoretical engineering. Mechanical engineering
In the design of complex equipment we observe a replacement of the traditional processing means of geometric-graphical information by the paperless technologies. Thanks to that new opportunities appear to use of automated design systems. New technologies arise which associate with the use of electronic models of design object. The main advantage of using the electronic model of the product is possibility of its use in the different modules of the systems of continuous design of the class CAD/CAM/CAE. In the modern CAD/CAM/CAE-systems geometric modeling of objects, computer solution of geometrical and engineering-graphics tasks occupy the central place.
This article is devoted to working out of mathematical model of packing of a tape under the set scheme of reinforcing on the technological surface, considering changing width of the tape. Besides, some characteristics of the scheme of reinforcing are entered in article, and the trajectory of movement of the stacker of the tape on the set picture of packing of a tape is calculated. Modeling of packing of a tape of variable width by means of smooth display is developed for the first time. Existing geometrical models do not consider width of a tape absolutely or they are intended for a tape of constant width.
The paper considers a problem to find the optimal trajectory and a law of motion of the spreading mechanism of a numerical control winding machine for making complex-shaped constructions of fibrous composite. The problem is solved taking into account a real structure of tape of fibrous composite, restrictions on an allowable position of the spreading mechanism, a thread tension and a broaching speed of tape.
Keywords: winding; the geodetic; semigeodetic system of co-ordinates; the reinforcing scheme
Control and navigation systems
Accelerations measurement in aggressive environments and high temperature conditions, typically performed in aviation and space equipment, in particular in aviation engines, may be implemented using a quartz transducer based on optical tunneling effect (OTE).
A typical OTE-based quartz acceleration transducer consist of a reflecting quartz prism, a quartz sensor element (beam), a source of light, a light receiver and a processor. Measuring the gap between the quartz prism and the quartz beam provides information about the pressure in a controlled environment. The quartz beam fixed at one end or at both can be used as a sensor element in the OTE-based quartz force transducer, which would consist of the same elements as a quartz pressure transducer and would have the same method of measurement.
Some aspects of the influence of acceleration on the sensor elements of an OTE-based quartz transducer are considered in this article. It is shown that the sensor’s reflectivity and output parameters of a quartz pressure transducer depend on the measured acceleration range, as well as on the design parameters of the sensor and on the initial gap between the quartz prism and quartz beam. The size of the gap has an influence on the reflectivity. The bigger the initial gap is, the smaller the influence of the acceleration on the output parameters of the OTE-based quartz pressure transducer. On the other hand, a large initial gap has a negative influence on acceleration sensitivity. The graphs of correlation between the size of the gap and the value of acceleration are presented. The gap calculations formula includes the parameters of quartz Young’s modulus and Poisson’s ratio.
The measurement error due to the temperature on an OTE-based quartz acceleration transducer is calculated to be of a fraction of a percent. Its influence on the measurement range is also found and described. This results make it possible to use such transducers in aviation engines.
Keywords: aero engines, aggressive environment, high temperature, quartz transducer, acceleration, receptive element, beam,
Fire and explosion safety experimental investigations of Russian space applicated prismatic lithium — ion accumulators are carried out in SSC Keldysh Research Centre. The main aim of this study was the test of lithium — ion accumulators for ignition and explosion resistance in the case of external short circuit and shock generated by metal punch.
The first step before the main tests for external short circuit is to charge the lithium — ion accumulators by direct current until the achievement of 4,2 V voltage at the terminals. During the short circuit carrying out the accumulator terminals were bridged by copper conductor with resistance ~ 100 mOm.
The tests for ignition and explosion resistance in the case of external short circuit and shock generated by metal punch were carried out with the help of special device with impact energy up to 120 J, which is sufficient for piercing of accumulators 60 mm in thickness (the thickness of the steel case is 0,6 mm).
Experimental results of external short circuit tests have shown that the charged prismatic accumulators in predeformed and non predeformed conditions were heated up (up to 150 °C), however maintaining deformation and destruction didn’t happen, and, as a result of it, there is no noticeable influence on the surrounding equipment.
During the investigations for ignition and explosion resistance the critical test of lithium-nickel-cobalt-oxidic electrochemical system led to impossibility of further accumulator operating. As a result of this test there was an internal short circuit after penetration of metal punch in the charged accumulator. Internal short circuit of the accumulator led to heating up (more than 500 °C), destruction of a safety membrane and welded seams, exit of the evaporated electrolyte and electrodes material. Destruction has explosive character and makes essential impact on the surrounding equipment (high temperature of the construction, a stream of hot gas).
Keywords: short circuit, the lithium-ion battery, reliability, fire and explosion safety, temperature control
Technical cybernetics. Information technology. Computer facilities
This paper develops the method of quantitative assessments for the technical state of the object representing its stock performance, also measured as a level of degradation. Such state of the object is determined by the set of its essential parameters by means the continuous mathematical model that allows to identify dangerous situations.
The positions of the measured values of the parameters within their respective fields of tolerance define a quantitative assessment of the state of the object. It characterizes the level of normal functioning or broken state depending on the target function.
Calculating the quantitative estimates of equipment states involves the membership function which shape is determined by the statistical properties of the processes occurring in the equipment. Properties of the quantitative assessments of equipment states for the common cases studied as assessing the level of its efficiency, and it assess the level of the unhealthy state of the object under the test.
The proposed method can be used at the production phase of the complex electronic equipment lifecycle as a tool increasing the performance of the output control. It also can be used on the sale and post-sale phase of the lifecycle for productive maintenance and more successful repair of shipped equipment. The current decision of usage of the object until a future predefined destination moment is taken on the results of the predicting stock performance for the object for the time interval required for its task.
It was shown that the accuracy of quantitative assessments of the technical conditions calculated on the basis of the continuous model is considerably greater than the accuracy of qualitative assessments based on the discrete model. It provides clearer recommendation for a decision-maker, since they are built on the results of the inventory forecasting performance objects for times of tasks completed. The proposed method allows one to choose the best stock of the projected performance of the group of the same object.
Keywords: method of quantitative estimations of technical conditions, procedure of evaluation of the quality of functioning, discrete and continuous mathematical models of states of complex systems
Radio engineering. Electronics. Telecommunication systems
The purpose of the current paper is obtaining such initial placement for basic elements of integrated circuits which provides higher quality with less computation time compared to known methods; that will increase the efficiency of the optimization methods of the placement such as a method dichotomy or Steinberg’s method
This research is based on the fact that the function of the total links length (TLL) is described under normal distribution law. Authors introduce the probability that at least one placement in progressive series of some random allocations (M) has TLL at any given threshold. Further, using methods of the probability theory, authors obtain the formula that allows one to calculate the value of M based on the predefined threshold and its likelihood value.
The carried out modelling verified that the proposed algorithm yields to the initial placement of basic elements, which in an average differs from optimum no more than 12 percent, with probability 0,9973.
It has to be noted that it takes about 30 minutes for a powerful personal computer to find the solution of the typical task given for circuits containing about one hundred elements.
As far as most of computer time it taken to obtain another random unduplicated set of numbers from 1 to N the paper presents new method that allows decreasing the cost of this calculation significantly.
Keywords: placement, the method of random assignment, CMOS LSI dual-total length relationships, design automation, basic crystal matrix
The purpose of the current work is tо compare the computational complexity of the boundary element method and finite element method for the numerical example of thermal modeling of the technical object.
The rod with insulated lateral surface was selected as the object of investigation. For the correct comparison of the methods mentioned above for thermal modeling, there was derived concrete numerical expressions allowing to calculate the exact number of instructions that are implementing both methods for the typical computer system.
It is shown that one needs to solve the only linear equation with one unknown for the steady-state calculation of the temperature field provided by boundary element method at any given point of the inner rod. And such procedure typically requires only a few machine instructions. Overcoming the same problem using finite element method is minimally required to solve a system of three linear equations with three unknowns; this can take tens of machine operations.
Unlike similar works on this topic, the advantage of boundary element method over the finite element method is shown in this article with a simple example which allows one to understand clearly the cause of this advantage. The equivalency of results obtained with both methods confirms the linearity of the change in the thermal field of the object.
Keywords: boundary element method, finite element method, pin-fin heat sink, state variable, boundary conditions, the influence function, fundamental solution, the simplex-element, interpolation polynomial
Various aluminum alloys are widely used now days as main structural materials for aviation technique. It must be noted nevertheless that the aluminum structural elements operating in aggressive media must be protected by various paint-and-lacquer coatings having good anti-corrosive properties. The combination of aluminum bases and lacquer protections secures the strength, the longevity, the wearing-off strength, and the required functionality.
The mechanical behavior of the coatings is studied experimentally using the rectangular specimens made from the 1163 RDTV aluminum alloy. The gloss powder paint with no lacquer, the gloss powder paint with powder lacquer Limerton (France), the gloss powder paint with decorative lacquer layered using the Glitter technology, and the gloss powder paint with the protective ceramic-based nanostructured lacquer coating Ceramiclear Deltron D8105 (PPG Industries, USA) are investigated.
The Young modulus for the coating was determined by the comparison of the Young modulus of the aluminum alloy 1163 RDTV with no paint-and-lacquer coating and the effective modulus of the coated specimen, so that the simple mixture rule for the composite materials can be used. It is found that the difference between the uncoated specimen’s modulus and coated one is about 10-15%, therefore the precision of the coating’s modulus estimation significantly depends on the stress and strain measurement during the experiments. It can be noted that the good repeatability of measurements for all specimens with different underlayers’ thicknesses was observed. The experimental stress-strain diagrams were similar both in elastic and yield zones of deformation.
The performed analysis if the experimental data has shown that the gloss powder paint with no lacquer has the maximum Young modulus and the lacquering results the reduction of the modulus of the coating. The similar results were obtained for the coated iron specimens.
Keywords: experiment, tensile tests, aluminum alloys, protective coating, powder paints, lacquers, young modulus
A mathematical model, an algorithm, and a software for the numerical simulation of heat state of heat protective composites undergoing various physical and chemical transformations under high temperature aero and gas dynamic heating of hypersonic (M>5) flying vehicles’ structures. Several high-temperature physical and chemical processes are taken into account, the normal heating of composites up to 600K, the thermal destruction (pyrolysis) of binding agents with generation of porous residuals from thin-fiber reinforcements and pyrolysis gases filtering through porous structures to outer surfaces streamlined by hypersonic flows, and the injection of these gases into the hypersonic flow. At the temperature of phase transform reached by the heated porous residual the mass loss such as the flowing, the evaporation, and the sublimation effected by the friction in the hypersonic boundary layer begins. The existence of two transient interfaces of phase transform of the composite around the thin area of the pyrolysis and the multi-dimensional transient heat and mass transfer with nonlinear and anisotropic thermal and physical properties have to be taken into account.
The proposed model considers all the mentioned above specificities of the process and it is based on the new pyrolysis and nonlinear filtration laws.
A numerical simulation algorithm is based on the new absolutely stable method of variable directions with extrapolation designed for the solution of multi-dimensional transient problems of heat and mass transfer in anisotropic bodies such as composite materials. The used method is the most stable and has no known analogs for nonlinear problems with mixed differential operators.
A software complex based on the described mathematical model and numerical simulation algorithm is developed using the PASCAL language and the DELPHI programming system. The software complex is constructed as the managing program allowing one to analyze the input data and to construct the oriented graphs of program realization of subcases of the general mathematical model. The nodes of the graph are the program modules, and the graph edges are the functional links between these modules. The proposed structure allows one to solve more than a hundred of various problems of heat and mass transfer for thermal protective composite materials heated by aero and gas dynamic flows.
Some different numerical simulations of various multi-dimensional thermal fields in heat protective composites subjected to the aero and gas dynamic heating and undergoing the phase transitions are performed using the developed software. Some results are presented in this article.
Keywords: composite materials, heat and mass transfer, typersonic flying vehicles, heat protection, aero and gas dynamic heating, algorithm, software complex
Economics and management
Considered the state and prospects of development of management processes basis on the requirements of the manufacturer of modern aircraft. This requires development of adequate tools for organization and management of domestic aviation systems design with sufficient organizational, financial and spatial flexibility.
The purpose of the work is to identify the factors defining the need for changes in organizational and administrative processes at aviation systems design, and to offer an approach to development and acceleration of design processes, to reduce a new planes development time cycle, and to improve the quality.
The result of the research as follows:
— building up requirements for design planning and management process in modern conditions;
— describes the level of functional design V model for design at all stages of lifecycle;
— in technologies of the system for engineering outlines the steps of the configuration management functional systems.
The spheres of application of the research results are management and planning systems of design organizations as well as the enterprises working at an initial phase of development and design of innovative production.
Keywords: model life-cycle management processes, system engineering, V design process, strategy, organization