SCIENCE & EDUCATION

The paper purpose is to study and find the ways to improve the reliability of onboard laser ranging system (LRS) used to control the rendezvous and the descent of spacecraft. It analysizes the key factors influencing the reliability LRS. The basic assumption is that the number of pulses of pumping diodes determines the solid state laser resource. The paper investigates a reliability function of LRS affected by the pulse repetition frequency, that depends on the measurement error of approach velocity and distance between the spacecrafts. The paper gives a quantitative evaluation of increasing the reliability function owing to the developed methods to detect a passive spacecraft using LRS with no optical-mechanical scanner.

The article studies a neural network approach to obtain the statistical characteristics of the input vector signal and noise implementations at ill-conditioned matrices of correlation moments to solve the problems to select and reduce the vector dimensions of informative features at detection and recognition of signals and noise on the basis of regression methods. It considers a problem concerning the matrix condition of the correlation moment of informative signal features and a possibility to apply the neural networks in theoretical studies. Neural network algorithms are used to obtain the necessary statistical data for ill-conditioned matrices of correlation moments of informative features. It is shown that the weights obtained at training the neural network with no zero weights are the regression coefficients of the initial parameters of informative features input.

The paper presents the research and development results concerning the universal algorithm for automated synthesis of centered optical systems of double conjugation in the paraxial region. The initial axial thicknesses for the initial scheme have been taken from the system designed by Hopkins. With a lack of appropriate solution the spacing is changed by some value. As a result of using the universal automated algorithm two different systems have been obtained. Both systems have two pairs of conjugate planes with changeable magnification. The kinematics of components movement has been calculated for both cases.

The paper presents a comparative analysis of the sounding range of wind correlation lidar in ultraviolet, visible, and near infrared spectral bands. It shows that a visible spectral band is the most advanced one to provide a maximum sounding range of wind correlation lidar in earth atmosphere. If there are specific requirements for wind correlation lidar, for example, a requirement is that a wind correlation lidar should operate at the eye-safe laser sounding wavelength then the efficient work of wind correlation lidar may be maintained in ultraviolet and near infrared spectral bands with the sounding range reduced a little bit.

The article describes a principle that may become a regular basis to use the noninvasive methods to measure parameters of steady-state heat transfer in living tissues, excluding the influence of unknown parameters such as biological heat sources and blood temperature. It presents a theoretical analysis and examples to implement the set out principle and proves technically a possibility to use this principle to determine the heat conductivity and perfusion of blood in human dermal epithelium. Furthermore, the article shows that the noninvasive determination of other parameters of biological tissue that influence on the steady-state heat transfer is possible.

The article described a technique for calibrating accelerometers unit on special test stands. The developed method allows to the determining the bias accelerometers unit, errors of scale factors accelerometers unit and angles of non-orthogonal accelerometers unit without presenting stringent requirements for high-precision testing equipment. Obtained by measuring the provisions of a test bed to which you want to set a block of accelerometers to obtain estimates of the instrumental errors of the block accelerometers. However, that requires precise measurement outputs of the accelerometers.

The article presents a method to form the non-periodic selection functions in the short-range coherent pulse Doppler radar information systems with random signal phase-shift keying (manipulation) in transmitting and heterodyne channels. It studies statistical characteristics of Doppler signals received when reflecting from the point object that is located inside the first and arbitrary remote strobes at synchronized random carrier phase-shift keying in transmitting and heterodyne channels. The article shows an expansion of the relative bandwidth of energy spectrum of a Doppler signal received after reflecting from the point object from an arbitrary remote strobe, except for the first one. To form a non-periodic selection function is possible via the recognition method for the Doppler signal implementations using the relative bandwidth of energy spectrum and via the application of a regression tract to process intervals between zeroes of implementations.

Current systems for monitoring leaks from petrol pipes can detect large leaks only, and their sensitivity limit is about 1% of the whole petrol pipe’s capacity. In this paper, a problem of remote detection of small leaks (less than 1%) from petrol pipes was considered. One of possible variations of such a system is a monitoring system of oil pollution at the earth surface along the petrol pipe. In this paper experimentally obtained data such as fluorescence spectra of oil products (crude oil, light-end oil products, heavy oil products), various earth surfaces (soil, vegetation, water, asphalt) and oil products spilled over various earth's surface were used for the excitation wavelength of 266 nm. It was shown that use of the laser method based on detection of fluorescence radiation within three narrow spectral bands and a neural network algorithm of measured data processing allowed one to detect oil pollution on the earth surface with a probability of correct classification close to 1 and low probability of false alarm.

This article considers a possibility of using a mathematical apparatus of direct-current fields for modeling distribution of the magnetic field vector during calculation of quasi-static fields of eddy current conversion units produced by an alternating current. Equivalence of field patterns was proved; it was also shown that there is no influence of the frequency of an alternating current which powers the eddy current conversion unit on the filed pattern for attachable parametric transducers of an arbitrary shape in free space. Theoretical justification was given for various frequencies along with experimental verification.

This article describes full-scale tests of a prototype of a IR Fourier spectral-radiometer for remote atmospheric sounding. The article presents an experimental procedure, which would allow one to determine the efficiency of the device and its metrological characteristics. Additionally, the article presents results of tests with the use of test objects such as films made of different polymer compounds (polyester, Teflon, polyethylene, polystyrene) with known thickness, as well as vapor of ammonia (NH3) and sulfur hexafluoride (SF6) in gaseous phase. The spectra of test objects were registered against various background objects - a clear sky, a cloudy sky, a model of a black body with a known temperature.

This article presents a possibility of applying optical methods - for instance, a method of infrared diaphanoscopy, to detect inflammation in tissues of a mouth cavity at the stage of primary damage. The authors investigated the main exogenous and endogenous factors of inflammatory diseases of mouth cavity tissues, the mechanism of their emergence and expansion; the behavior of tissues’ optical and physical properties in the mouth cavity at various stages of inflammation was demonstrated; interrelation of those properties with the change in chromophore concentration with the expansion of the inflammatory process was also revealed.

In this paper the authors consider an algorithm for determination of ground objects’ location in the space-based passive radar system under conditions of the input data of low accuracy. Use of a passive radar allows to determine the location of ground objects, in particular, active radiolocation stations by its radiation under conditions of low energy consumption on board of a spacecraft. In this regard, bearing accuracy is quite low at the output of a signal processor. Lack of computing resources, which is typical for embedded systems, must be also taken into account. These features make it difficult to synthesize an effective location algorithm carrying out secondary radar data processing. In this paper theoretical theses of the location algorithm and particularities of its implementation within a space-based embedded computer are presented. In particular, it is subject to bearing accuracy achievable in the algorithm and processing of vast surveillance zone which is challenging due to lack of computing resources.

It was proposed to carry out performance evaluation of active vibration damping in multi-mass dynamic systems of metal structures of excavators and jib cranes when damper’s power body is located between oscillating masses, in comparison with external resistance damping. Results of synthesis of damping effect which provides a specified degree of oscillation decline in metal structures under force excitations and self-oscillations were presented. It was shown that allocation of the active damper’s power body between the working body’s installation unit and metal structures of machines allowed one to improve dynamic properties of the specified machines significantly.

Verification of an interaction model of ultrasonic oscillatory system with biological tissues developed in COMSOL Multiphysics was carried out. It was shown that calculation results in COMSOL Multiphysics obtained with a use of “Finer” grid (the ratio of the grid step to a minimum transversal section area of a model ≤ 0.3 mm^-1) best of all qualitatively and quantitatively corresponded to practical results. The average relative error of obtained results in comparison with the experimental ones didn't exceed 4.0%. Influence of geometrical parameters (the thickness of load) on electrical admittance of ultrasonic oscillatory system interacting with biological tissues was investigated. It was shown that increase in the thickness of load within the range from 0 to 95 mm led to decrease in calculated values of natural resonance frequency of longitudinal fluctuations and electrical admittance from 26,58 to 26,35 kHz and from 0,86 to 0,44 mS.

This article deals with real-world problems of secondary digital processing of radar data in an autonomic survey radar subsystem. Essential aspects and complexities of trajectory processing in such kind of systems were revealed. A review of existent algorithms for locking trajectories as an important stage of secondary processing was presented. An algorithm for locking target trajectories, which takes into account low accuracy of the input data, was developed; this algorithm was considered to be optimal by the maximum likelihood criterion. Mathematical simulation which demonstrates satisfactory performance of the proposed algorithm, including the case of data with an intense noise, was carried out.

In this article the authors propose an investigation method of changing current–voltage characteristic of a resonant tunneling diode influenced by degradation processes in its structure. An investigation of degradation of an AlAs/GaAs resonant tunneling diode structure at the temperature of 300°C was conducted. The findings show that in these conditions change in current–voltage characteristic of the resonant tunneling diode is mainly due to degradation of ohmic contacts. An analytic dependence of the resonant tunneling diode AuGeNi ohmic contact resistance on time and temperature was determined.

The authors analyzed laser-induced fluorescence spectra of healthy vegetation and vegetation under stress at fluorescence excitation within the blue spectral range. It was shown that a use of fluorescence excitation within the blue spectral range and the registration of fluorescent radiation in three narrow spectral ranges with central wavelengths of 680, 690 and 740 nm allowed one to detect reliably whether the vegetation is under stress. Ratios of the intensity of fluorescence radiation at the wavelengths of 680, 740 nm and at the wavelengths of 690, 740 nm were used as the identifying factors of plant stress.

Thermal power loading of a thermoelectric module (TM) in operation was investigated; the weakest elements were revealed. Analysis of thermal deformations arising in the branches of TM was carried out. Influence of various deformation types on the stress-strain state of the TM’s branches was studied. A mathematical model for calculating stresses in the branches of TM was developed. Calculation results obtained with the use of the proposed model were presented. Influence of geometric characteristics of the TM’s branches and manufacturing tolerance on stresses in the branches was also investigated. Recommendations were given on the design of TM on the basis of the obtained results.

The paper presents results of developing an automated complex for determination of the hormonal status of breast cancer using an immunocytochemistry method. The complex performs automated scanning of medication and image capturing by means of an automated computer-driven microscope, as well as automated image analysis which results in estimation of Allred’s scores; the developed complex is capable of visual verification and correction of analysis results if it is necessary. Experimental studies demonstrated high repeatable accuracy of automated analysis results and agreement of automatically drawn conclusions on the hormonal status of breast cancer with the ones obtained by cytologist during visual microscopic examination.

The paper deals with creating a mathematical model of motion of abrasive grains in the abrasive extrusion processing (AEP). This will extend capabilities of this technology. The essence of the AEP is in puncturing (extrusion) of an abrasive paste along the processed surfaces (in most cases through holes) and material removal by abrasive particles contained in the paste which consists of abrasive grains and a binder in a viscous-elastic liquid. Use of existing models cannot explain the essence of the grain’s motion and its impact on the processed surface material. The author substantiates the need for introduction of elastic characteristics of the bonding liquid into the model’s main equation, along with the concentration index of the abrasive grains.