Статьи журнала - Siberian Aerospace Journal
Все статьи: 341
On the function of time distribution of a complex computing system uptime
Статья научная
Any space computing complex is a complicated system. A complicated system is understood as a set of functionally related heterogeneous devices designed to perform certain functions and solve problems facing the system. One of the important characteristics of a system is its uptime. This characteristic is often considered to be a random variable. However, such a mathematical model is quite limited, since the uptime depends on many characteristics (parameters) that describe a system. Therefore, the uptime can be assumed to be a continuous random field (that is, a random function of many variables). It is this approach that is used in this work. If there are certain restrictions on the uptime of a computing system, upper estimates are found for the distributions of a random number of system failures. Therefore, the problem of estimating Gaussian field distribution in Hilbert space arises. Two theorems that allow calculating the probability of a Gaussian vector falling into a sphere of a given radius are proved in the paper. The paper is devoted to the reliability of a computing system. The random number of a computing system failures v(r) is a characteristic of its reliability. The v(r) distribution is the distribution of the sum of a computing system random uptime. It is impossible to write down the distribution v (r) explicitly. Therefore, one has to look for an estimate of these distributions from above. Assuming that the uptime of a computing system is the sum of many variables, the authors of the paper obtained the following results: it is shown that the problem of estimating the distributions of a random number of system failures can be considered as the problem of estimating the convergence rate in the central limit theorem in Banach spaces; if there are certain restrictions on the uptime of a computing system, upper estimates are found for the distributions of a random number of system failures. The estimates obtained can be used for further research in the theory of computing systems reliability. Knowing these upper estimates, it is possible to predict the level of average costs for computer systems restoration, as well as for the development of special mathematical and algorithmic support for analysis systems, for management, decision-making and information processing tasks.
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Статья научная
The results of the study of the damping capacity of manganese-copper alloys based on the Mn – 40 % Cu alloy with additives (0.5 – 1.5) % zirconium in the field of amplitude-independent damping are present-ed. Mn – Cu alloys with high damping capacity can be effectively used to reduce vibration and noise. Stud-ies on the influence of a number of alloying elements on the magnitude and stability of the damping capaci-ty of Mn – Cu double alloys in the field of small deformations of relative shear are not enough. In the pa-per, the influence of one of these elements, zirconium, was elucidated. Mn – Cu alloys were smelted in an induction furnace. From the ingots cast into cast iron molds, samples for studies with dimensions (11 × 15 × 117) ± 1 mm were obtained by mechanical cutting. The samples were subjected to aging at a temperature of 643 K for 0.5–40 hours. The damping capacity of Mn – Cu alloys (the logarithmic decrement of attenua-tion of oscillations) was studied for longitudinal oscillations of samples in the frequency range 14–17 kHz and the amplitudes of the relative shift (1 ... 3) × 10–6. It has been established that alloying the Mn – 40 % Cu alloy with zirconium from 0.5 % to 1.5 % does not increase its damping capacity in the cast state, as well as in the cast and aged at a temperature of 643 K for 40 hours. It was found that the minimum values of the frequencies of resonant vibrations of samples of Mn – Cu alloys correspond to the maximum levels of the damping capacity of these alloys. Itʼs shown that the high damping capacity of cast and aged alloys at 643 K for 40 hours Mn – 40 % Cu, Mn – 38.5–39.5 % Cu – 0.5–1.5 % Zr after natural aging at 293 K for 7 months decreases by 2.0–2.6 times.
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On the issue of hydrodynamic braking efficiency dur-ing high-velocity tests on a rocket-rail track
Статья научная
At present, the creation of high-velocity aircraft is a promising direction in the development of aircraft and armament both in Russia and abroad. The increase in velocity characteristics of newly developed sam-ples imposes new requirements on test bench equipment, including rocket-rail tracks. The requirements are growing both for the acceleration and braking means, which ensure the tested materiel safety. The proposed work deals with a hydrodynamic braking method used in high-velocity dynamic tests on a rocket-rail track at the Federal State Enterprise “State Governmental Scientific-Testing Area of Aircraft Systems named after L.K. Safronov". The paper gives the description of the braking devices, presents the dependencies determining the calculated values of the braking force developed by them, and describes the braking intensity control methods, which increase the efficiency and safety of braking as well as expand the permissible speed range of the hydrodynamic braking device application. The method of increasing the efficiency of the braking devices functioning by using a special form of its working part profile is presented. The corresponding examples of the braking modes are given for a comparative assessment of the braking efficiency parameters when using braking devices with special and triangular profiles. The working part profile of the hydrodynamic braking device calculated according to the proposed method provides more efficient and safe braking compared with the previously used triangular profile, by maintaining a constant stopping force in a wide velocity range.
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On the location of spacecraft in a given number of orbits
Статья научная
Space vehicles are an expensive product. For example, just putting such a device into orbit costs at least one hundred million dollars plus the cost of the satellite itself and scientific equipment it carries. However, the cur-rent state of human civilization does not allow us to do without the presence of satellites in orbit. There were 2,062 active satellites in the international database as of March 2019. Compared to 2018, the number of new devices increased by 15 %. Experts warn that in the coming years, the world is expecting a «satellite boom» with a projected increase in the number of devices of about 15–30 % annually. All these satellites are rather different. Currently, several orbits are used for placing satellites on them, depending on the tasks they solve. A geostationary orbit is used for live television broadcasting. Low satellite orbits are used for communication between satellite phones. There are some orbits for navigation systems (GPS, Navstar, GLONASS). Naturally, under these conditions, there is a prob-lem of placing spacecraft over a given number of orbits, with some restrictions on the location of the spacecraft in certain orbits, depending on the purpose of the spacecraft. The solution to this problem is considered on the condition that the number of spacecraft coincides with the number of possible orbits in which they can be placed with some additional re-strictions on the possibility of their placement in orbit. Several solutions to this problem are obtained that allow us to calculate the number of possible combinations for such placement of spacecraft over a given number of orbits.
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On the possibility of flight of a single-stage rocket to the planets of the Solar system
Статья научная
A new concept for building a small-sized rocket engine containing a special gas ionizer in the combus-tion chamber to increase its conductivity to an optimal value with a corresponding improvement in the fuel combustion process is proposed. A simplified calculation for the relative velocity of gases in a conical noz-zle is given when heating the supersonic flow of gases by plasma in a conical nozzle by means of a power-ful, electromagnetic, high-frequency field, and the influence of some technical parameters on the efficiency of the rocket's flight is also considered. A comparison of the flight altitude of a rocket with plasma heating of the gas flow in a conical nozzle with a scale model corresponding to the well-known single-stage Zenit rocket with the same weight and geometry, taking into account air resistance for the cargo version of the rocket with one small-sized engine, is made. The result is a significant reduction in fuel consumption and an increase in the maximum flight altitude by 2 times with an increase in specific impulse by 2.7 times, other things being equal. It is estab-lished that under certain conceptual parameters, it is possible to rapidly accelerate and fly a single-stage cargo rocket with a launch weight of 17.25-20.00 tons to the planets of the solar system directly from the Earth's surface using a bunch of engines of the same type. The use of many of the same type of small-sized engines allows you to abandon the Laval nozzle in favor of a simple conical nozzle, which reduces the size of the rocket as a whole. This is determined by the need to reduce the diameter of the conical nozzle in order to achieve a greater specific heating power of the plasma compared to the specific power of the fuel burned in the combustion chamber. It is also proposed a complete rejection of the steering engines, the function of which will be performed by part of the engines located closer to the diameter of the rocket. As electric generators, it is proposed to use promising prototypes of electric generators MEG-6NS, MEG-15NS and others, the company "NaukaSoft", with good weight indicators that allow in the future producing such a liquid propellant rocket engine (LPE) of small dimensions. The redistribution of part of the fuel used to produce electricity is compensated by a significant increase in the specific impulse of the LPE to increase the speed and overall efficiency of the flight with an optimal ratio of the amount of fuel to the weight of the rocket before refueling.
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One class of solutions to the equations of ideal plasticity
Статья научная
Much attention is given to the study and solution of nonlinear differential equations in the modern mathematical literature. Despite this, there are not many methods for researching and solving such equations. These are point and contact transformations of equations, various methods of separating variables, the method of differential connections, the search for various symmetries and their use to construct solutions, as well as conservation laws. The paper considers a nonlinear differential equation describing the plastic flow of a prismatic rod. A group of point symmetries is found for this equation. The optimal system of onedimensional subalgebras is calculated. Conservation laws corresponding to Noetherian symmetries are given, and it is also shown that there are infinitely many non-Noetherian conservation laws. Several new invariant solutions of rank one, i. e. depending on one independent variable, are constructed. It is shown how classes of new solutions can be constructed from two exact solutions, passing to a linear equation. Thus, in this short article, almost all methods of modern research of nonlinear differential equations are involved.
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Статья научная
One of the promising types of spacecrafts are large-size transformable reflectors. Such apparatuses are delivered to a target orbit folded, and then deployed to a working condition. The large aperture allows sig-nificantly expanding the capabilities of the antenna. In this case, the tasks arise of a smooth and reliable deployment, adjusting the shape of a radio-reflecting net, and adjusting the orbital position. Due to the fact that the deployment process takes a long time, accounting for disturbing influences is an important prob-lem. The presence of radiation, large temperature differences, solar wind affect the entire system and main-ly on the directional diagram. It is also necessary to smoothly deploy the structural elements, since with an increase in the diameter of the radio-reflecting surface, the moments of inertia of the antenna increase, which leads to prolonged oscillations. In this paper, the process of deployment of the reflector spokes in the presence of disturbances and measurement errors is considered. The solution to the problem is presented using the separation theorem. To estimate the parameters of the system in the presence of measurement noise, the Kalman filter is applied. Its performance is shown at various values of the noise intensity. A ran-dom process such as white noise was selected as external disturbances and measurement noises. The con-trol problem is solved using the optimal control algorithm according to the hierarchy of target criteria. The possibility of minimizing energy costs by means of interval switching on of measuring sensors is shown. The results of numerical simulation are presented.
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Статья научная
Currently, the development of large-sized space structures and, in particular, transformable reflectors is actively developing. A feature of these devices is a small volume during transportation and large dimensions in the expanded working condition. Therefore, it is important to carry out a reliable and smooth deployment, adjust the shape of the active radio-reflecting surface with a given accuracy, and adjust the orbital position. In outer space, the system is constantly exposed to radiation, there is a large temperature difference in near-Earth orbit, there is a solar wind, which mainly affects the radiation pattern. In this paper, the process of deployment of the reflector spokes in the presence of disturbances and measurement errors is considered. The solution to the problem is presented using the separation theorem. To estimate the parameters of the system in the presence of measurement noise, the Kalman filter is applied. Its performance is shown at various values of the noise intensity. A random process such as white noise was selected as external disturbances and measurement noises. The control problem is solved using the optimal control algorithm according to the hierarchy of target criteria. The possibility of minimizing energy costs by means of interval switching on of measuring sensors is shown. The results of numerical simulation are presented.
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Optimization control actions for the electrolytic method of aluminium production
Статья научная
The most common indicator of the aluminium production process managing efficiency is the cost of the metal production, but this concept includes a lot of components. First, this is the cost of raw materials and electricity in this region, as well as the labour cost per ton of products, consumption coefficients of raw materials and energy, capital costs for construction and repairs, waste disposal cost, environmental payments, etc. At the same time, there is no single functional of the process quality, depending on technological parameters, that is, the problem of complete and relatively strict mathematical process optimization as a whole is currently not solvable, not only because of its volume, but because of the lack of a complete efficiency model. In this study, particular efficiency criteria are considered, the improvement of which is aimed at the optimization model of control actions developed by the authors, which are selected based on the possible levers of the current automated process control system (APCS) for aluminium electrolysis. All tests were carried out on Virtual cell software without transfer to a real control object.
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Optimization the position of the spacecraft instrument panel mounting points based on modal analysis
Статья научная
The paper presents optimization of the location of interface points of the spacecraft instrument panel using modal analysis, as well as a quasi-static calculation of the panel under study, confirming effective-ness of proposed changes in the panel design. The instrument panel is a three-layer honeycomb structure consisting of two aluminum plates and a honeycomb filler. Cellular panels have a number of advantages: a small weight of the structure, high rigidity, specific strength. Using finite element modeling, the range of natural frequencies and vibration patterns of the instrument panel was determined, which made it possible to determine optimal location of the panel fixing points to the spacecraft body to increase the lower limit of natural frequency range and increase its carrying capacity.
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Optimizing the readability of tests generated by symbolic execution
Статья научная
Taking up about half of the development time, testing remains the most common method of software quality control and its disadvantage can lead to financial losses. With a systematic approach, the test suite is considered to be complete if it provides a certain amount of code coverage. At the moment there are a large number of systematic test generators aimed at finding standard errors. Such tools generate a huge number of difficult-to-read tests that require human verification which is very expensive. The method presented in this paper allows improving the readability of tests that are automatically generated using symbolic execution, providing a qualitative reduction in the cost of verification. Experimental studies of the test generator, including this method as the final phase of the work, were conducted on 12 string functions from the Linux repository. The assessment of the readability of the lines contained in the optimized tests is comparable to the case of using words of a natural language, which has a positive effect on the process of verification of test results by humans.
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Parameters of rocket engine chambers, obtained by selective laser melting
Статья научная
When designing and testing a low-thrust rocket engine (LTRE), one of the most important tasks is to ensure the quality of materials, which, in turn, affects the reliability of the product. Currently, additive technologies for manufacturing parts from metals are actively developing. This direction is relevant for rocket and space technology products to reduce weight and increase the reliability of products. The article presents the results of studies of the chemical composition and mechanical characteristics of the material of the low-thrust rocket engine demonstrator chamber, manufactured by selective laser melting from metal powder. The properties of products made from Inconel 718 metal powder were studied. Samples were made and the chemical, mechanical and structural characteristics of the material were studied. Based on the test results, two LTRE samples were printed. LTRE chambers were tested for vibration loads, strength and tightness. Increased porosity and roughness of the test material of the engine chamber were noted. When analyzing a number of parameters of the selective laser melting technology, an experimental selection of printing parameters was carried out and the most significant factors affecting the print quality (surface roughness and porosity) were identified. Based on the results of the work carried out, four groups of controlled printing parameters were identified that affect the properties of the resulting material. The work also provides recommendations on printing modes and characteristics to obtain the highest quality parts.
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Parametric analysis of the anisogrid body of the spacecraft for cleaning the orbit of space debris
Статья научная
The article presents an approach to solving the problem of designing a spacecraft for cleaning the orbit of space debris (space garbage collector-KSM), the body of which is made in the form of a cylindrical mesh anisogrid shell. The design task is to select the optimal parameters of the anisogrid body of the KSM (the shape and cross-sectional area of the ribs, the number of annular and spiral ribs, material characteristics, etc.) that provide the necessary strength and stability of the structure with minimal weight. During the design process, a parametric analysis of the anisogrid housing of the space garbage collector was carried out. By varying the number and angle of inclination of unidirectional spiral ribs, we find the optimal design scheme that satisfies the specified safety and stability coefficients. Parametric analysis of the KSM body includes modeling of the main weight and strength parameters: determination of the stress-strain state of the structure, values of the body’s natural frequencies, determination of the bending margin from the longitudinal force, determination of the body mass. The analysis of the load-bearing capacity of the anisogrid housing of the space garbage collector was carried out by the finite element method using the MSC Nastran software package. A finite element mesh model was created from a two-node spatial finite element bundle. The disk attached to the end of the shell was modeled using a rigid finite element. The size of the final beam element for all shell models was the same and equal to 10 mm. During the parametric analysis, three variants of the mesh composite structure with a different number and angle of inclination of unidirectional spiral ribs were considered. Based on the results of parametric analysis of the spacecraft body, its geometric dimensions are determined and the mass of the spacecraft structure as a whole is minimized.
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Parametric analysis of the strength of a solid propellant rocket engine nozzle
Статья научная
The paper presents an approach to solving the problem of designing a solid propellant rocket engine (SPRE) nozzle using such a design feature as a carbon fiber insert plate. The design task is to select the optimal parameters of the plate shape and thickness, providing the required load-bearing capacity with minimal mass. During the design process, a parametric analysis of a SPRE nozzle with a carbon fiber insert plate was carried out. By varying the thickness of the plate, an optimal design scheme that corresponds to the specified safety and stability factors was selected. Parametric analysis of an insert plate made of a composite material includes modeling of its main weight and strength parameters: analysis of the stress-strain state of the structure, values of natural frequencies, determination of the buckling margin, and determination of a SPRE nozzle mass. The analysis of the load-bearing capacity of a SPRE nozzle with an insert plate made of a composite material was carried out by the finite element method using the SolidWorks Simulation software package. When conducting a parametric analysis, two variants of a SPRE nozzle with and without an insert plate were considered. According to the results of a parametric analysis of a SPRE nozzle, its geometric dimensions were determined and the structure mass was minimized.
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Статья научная
A mathematical model of the aircraft avionics thermal state describing the heat exchange of the onboard equipment housing with a honeycomb structure made of a carbon fiber composite, the process of heat transfer of the onboard equipment elements and the air is developed. The considered heat transfer process in a heterogeneous medium is described by the boundary value problem for the heat equation with boundary conditions of the third kind. To solve the direct problem of the onboard equipment housing with a honeycomb structure thermal state, the Monte- Carlo method on the basis of the probabilistic representation of the solution in the form of an expectation of the functional of the diffusion process is used. The inverse problem of the honeycomb structure heat exchange is solved by minimizing the function of the squared residuals weighted sum using an iterative stochastic quasigradient algorithm. The developed mathematical model of the onboard equipment in the unpressurized compartment thermal state is used for optimizing the temperature and airflow of the thermal control system of the blown onboard equipment in the unpressurized compartment of the aircraft.
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Статья научная
The analyzes of the requirements to 3D-configuration pipelines production at the rocket and space industry enterprises is done. A review of different approaches to pipe bending technology (with heat treatment and without heat treatment) is carried out. The object of the study is the bending process and a universal bending machine for pipelines’ production of complex configuration. The article is divided into four sections, which consider the key factors, causing directly the effectiveness of the technological operation of pipeline bending of a complex 3D-trajectory. An overview of no-temperature shaping of the pipeline is given in the first section. The requirements to the technology, excluding: corrugation, flattening, stretching and thinning of pipeline walls during their bending, are considered. The actual regulatory documents and industry aerospace standards, regulating production of pneumatic and hydraulic pipelines are given. An example of calculating the minimal allowable bend radius of the pipe, depending on the diameter and thickness of the pipe wall, is given. The requirements to unification of the pipe size production and gaps are listed. The dependence of the maximal allowable internal pressure in the pipeline is shown. The requirements to equipment, used in pipeline bending and to the design of the pipe bending machine are considered. In the second section, the possibilities of temperature influence on the pipe bending process are viewed. The analysis of patent and technical literature and six possible methods of effective thermal effects are presented: heating of the whole pipeline length, narrow zone heating of the bend pipe place, water cooling with nitrogen in the pipe, laser-cooling of atoms of the pipes, application of the petroleum products on the place of heating of the pipe and using of modern fillers inside the pipe to change its temperature. In the third section the tasks of the development of a universal bending machine are set; the system of the algorithm of the universal bending machine operation is considered; the system of algorithm of the bending machine operating with CNC is shown. The General functional scheme of the bending machine and the sequence diagram of the equipment operation is given.
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Статья научная
The article proposes an approach to developing the architecture of a service-oriented information processing system, modeling and process control. The system, which is being developed, is a tool for identifying, predicting and controlling discrete-continuous processes. Its mathematical apparatus is based on nonparametric algorithms of identification and control. The software architecture includes the following main modules: the module for processing data, modeling and forecasting output process variables and the process control module. The first module includes data preprocessing algorithms: normalization, centering and analysis of outliers and omissions. The modeling module is an algorithm for research and recovery dependencies between process variables, process identification using nonparametric estimation of the regression function from observations. The last module is an implementation of nonparametric dual control algorithms. Control devices built on the basis of these algorithms perform functions of both object control and its study. The article discusses the application of architectural solutions based on two proven approaches in the field of software development: the composite approach and the service- oriented approach.. The main principles of composite architecture as a set of software systems with many characteristics that perform a specific task and service-oriented architecture as a modular approach to software development are described. The advantages of the applied composite service-oriented architecture over other variants of software architecture for control systems are shown, in particular, monolithic software architecture is compared with composite service-oriented architecture. This means that a researcher can use a single operation, which is a logically isolated, repeated task related to the production process of the enterprise. At the same time, it is necessary to ensure positive results when integrating with existing software products of enterprises which greatly complicates and requires the development of new components, as well as support for the "inherited" parts of the system.
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Piecewise approximation based on nonparametric modeling algorithms
Статья научная
In this research the issue of inertialess processes modeling is under study. The main modeling algorithm is the non-parametric recovery algorithm of the regression function. The algorithm allows to build a process model under conditions of low a priori information. This feature may be particularly important in modeling processes of large dimensions prevailing in the space industry. One important feature of the algorithm for nonparametric estimation of the regression function is that the accuracy of modeling using this algorithm highly depends on the quality of the observations sample. Due to the fact that in processes with large dimensions of input and output variable vectors observation sampling elements are in most cases unevenly distributed, the development of modifications to improve the quality of mod-eling is relevant. The modification of the nonparametric dual algorithm based on piecewise approximations has been devel-oped. According to the proposed modification, the process area is divided into sub-areas and a non-parametric esti-mate of the regression function for each of these sub-areas is recovered. The proposed modification reduces the impact of some observation sampling features, such as sparseness or voids in observation samples on the quality of the built model. The computational experiments were carried out, during which a comparison was made between the classical algorithm of non-parametric estimation of regression function and the developed modification. As the computa-tional experiments have shown, with uniform distribution of the sample elements of observations, the developed modification does not lead to the improvement of the quality of modeling. With a substantial uneven distribution of the observations sample elements, the developed modification resulted in a 2-fold improvement in the quality of the simulation. The results suggest that the proposed modification can be used to model complex technologi-cal processes, including those in the space industry.
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Plasmotron for coating internal surfaces of component parts
Статья научная
Plasma spraying is one of technologically appropriate, productive and effective methods of applying protec-tive coatings to component parts produced by aerospace, metallurgical and other industries, objects exposed to high temperatures, dynamic loads, aggressive media, etc. Plasma spraying makes it possible to apply quite a va-riety of materials, such as metals, oxides, carbides, nitrides, etc. to different surfaces. Certain problems may arise, though, in applying protective coatings to the inner surfaces of cylinders and complex parts of small size (about 100 mm). These complexities depend on the dimensions of the plasma generator proper. There are no home-produced small-size plasma torches, they are all imported from other countries. That causes certain prob-lems with delivery, to say nothing of very high commercial price. One of the ways to improve the situation is to develop small-size plasmatrons capable of applying high-quality coatings to the internal surfaces of limited-size parts; that may significantly reduce expenses through import substitution. The effectiveness of the proposed device is in working out a method of applying high-quality coatings to the inner surfaces of orifices as small as 60 mm in diameter (operating a plasmatron of smaller size), as well as in significant cost reduction due to domestic production. Sample calculations show that the price of that plasma-tron type will not exceed 0.5 million rubles.
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Point defects in nematic liquid crystal materials with conical anchoring at the interface
Статья научная
The topological point defects in nematic liquid crystal materials have been studied. The method of oblique light incidence has been proposed to determine an azimuthal director angle of an achiral nematic as well as a chiral nematic (cholesteric). The idea of the method is based on the dependence of the optical phase difference between ordinary and extraordinary light beams on the azimuthal director angle at the layer center at oblique incidence of light on a structure in which the polar director angle of a nematic liquid crystal is not equal to 0° or 90° (conical boundary conditions). It has been shown that the phase difference reaches a maximum at a zero azimuthal angle at the center of the layer regardless of the total twist angle of the director. The developed method has been used to analyze topological defects formed in the nematic and cholesteric layers under conical boundary conditions at the interface. The director field distributions of nematic and cholesteric near the surface point defects (boojums) with topological charges m = +1 and m = –1 have been drawn based on the experimental data. The proposed method of oblique light incidence can be used to analyze a wide class of the achiral and chiral liquid crystal media of various types: smectics, nematics, and cholesterics with tilted or hybrid boundary conditions.
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