Search

Within the framework of the traditional scope of investigations in the field of acoustic measurements, we consider an autoregressive model of the vocal tract, which is a key link in the speech apparatus of human beings. We mention the existence of an urgent problem of guaranteeing the stability of the autoregressive model in systems with adaptation of their parameters to the observed speech signals of short duration. To overcome this difficulty, we pose the problem of testing the stability of the autoregressive model and adjustment of its parameters according to the results of testing. The required investigations are based on the original authors' technique of the formant analysis of vowel sounds of speech via the synthesis of a recursive shaping filter in the mode of free oscillations. For the solution of the posed problem, we propose a procedure aimed at testing the stability of the autoregressive model of vocal tract and adjustment of its parameters. The method is based on a two-stage algorithm of transformation of the autoregressive model of vocal tract. In the first stage of transformation, the stability of the autoregressive model is checked according to the impulse response of the shaping filter. In the second stage, if the stability of the autoregressive model is violated, its impulse response is modified as a result of the element-by-element multiplication by a variable exponential quantity asymptotically convergent to zero. We develop a regular algorithm for recalculating a modified impulse response into the adjusted vector of autoregressive parameters in the second stage of transformation. According to the results of experimental verification of the proposed method, we make a conclusion that the guaranteed stability of the autoregressive model of the vocal tract is attained with minimal distortions in the frequency domain. The obtained results can be useful for the development and improvement of the systems of automatic speech recognition, digital speech communications, artificial intelligence, and other information systems based on the use of data compression and speech encoding according to the autoregressive model of the vocal tract in the course of automatic processing of speech signals. [ABSTRACT FROM AUTHOR]

The article reveals the problem of mitigating an insider threat by creating a timebalanced security system in an organization. Based on Markov chain, the authors propose a basic model of interaction in an "organization - insider" system. The article analytically defines a ratio between the time of an insider attack and the time during which the organization's security system can neutralize it. The authors propose a concept of a multi-level system of organization protection, which takes into account the involved resources and practical skills of employees, as well as security services. At the end of the article, it is concluded that the proposed concept of the organization's protection system will be effective against potential insider attacks. [ABSTRACT FROM AUTHOR]

This research relates to the field of speech technologies, where the key issue is the optimization of speech signal processing under conditions of a prior uncertainty of its fine structure. The problem of automatic (objective) analysis of the speaker's voice timbre using a speech signal of finite duration is considered. It is proposed to use a universal information-theoretic approach to solve it. Based on the Kullback-Leibler divergence, an expression was obtained to describe the asymptotically optimal decision statistic for differentiating speech signals by the voice timbre. The author highlights a serious obstacle during practical implementation of such statistics, namely: synchronization of the sequence of observations with the pitch of speech signals. To overcome the described obstacle, an objective measure of timbre-based differences in speech signals is proposed in terms of the acoustic theory of speech production and its "acoustic tube" type model of the speaker's vocal tract. The possibilities of practical implementation of a new measure based on an adaptive recursive filter are considered. A full-scale experiment was set up and carried out. The experimental results confirmed two main properties of the proposed measure: high sensitivity to differences in speech signals in terms of voice timbre and invariance with respect to the fundamental pitch frequency. The obtained results can be used when designing and studying digital speech processing systems tuned to the speaker's voice, for example, digital voice communication systems, biometric and biomedical systems, etc. [ABSTRACT FROM AUTHOR]

The problem statement is given and the algorithm for solving problems of plasticity for axisymmetric bodies made of isotropic materials with properties depending on a stress mode and plastic loosening is described. The constitutive equations of the theory of deformation processes along the trajectories of small curvature containing two nonlinear dependences are used. One of them implements the relationship between the first invariants of stress and strain tensors, and the other one implements the relationship between the second invariants of the corresponding deviators. The effect of the dependence of deformation curves on the stress mode and the plastic change in the bulk strain on the results of calculating the stress-strain state of the shell is studied. [ABSTRACT FROM AUTHOR]

The task of comparison testing of time series power spectrum parametric estimates is considered. It is shown that an urgent problem that arises in solving it is the optimization of the parameters of spectral estimates under conditions of small samples of observations. To overcome this problem, it is proposed to use the system-wide concept of analysis through time series synthesis. Based on this concept, a regular method was developed for comparison testing of parametric estimates of the power spectrum that are obtained from a time series of finite duration. Within the method, solutions are accepted based on the results of testing statistical hypotheses about the homogeneity of two samples: the finite empirical one, compiled based on the results of observations, and an infinite virtual one, mathematically synthesized according to each individual parametric estimate in the series of spectral alternatives being examined. The principle of minimum informational divergence between samples according to the Kullback–Leibler criterion. An example of the practical application of the developed method is presented in the problem of discrete spectral modeling of speech signals. The ability of the method to identify patterns of unstable parametric estimates of the autoregressive type has been shown. The results obtained are intended for use in the field of speech acoustics, as well as technical and medical diagnostics, where parametric methods of spectral analysis are increasingly used in practice. [ABSTRACT FROM AUTHOR]

A technique to improve the convergence of the process of successive approximations in boundary-value problems of thermoviscoplasticity is proposed. The constitutive equations of the theory of simple processes and the theory of processes of deformation along small-curvature paths are used. It is assumed that the specific works of deformation of elementary volumes of the specimen and the body at certain values of the intensity of tangential stresses and shear strains are equal. A number of approximations in test problems of the shell theory and in a spatial problem under nonaxisymmetric loading are considered. It is shown that the proposed modification of the process of successive approximations halves their number. [ABSTRACT FROM AUTHOR]

The task of measuring the spectral density of power of a speech signal in sliding observation window mode is examined. A parametric approach to solving this task using an autoregressive data model is studied. The problem of optimizing the order of an autoregressive model under the conditions of small samples is studied. It is proposed to solve the problem using a hybrid method of spectral analysis based on sequential enumeration of a finite number of variants. The optimization criterion is formulated in terms of an inverse problem: from the speech signal to the voice source. It uses the scale-invariant measure of the spectral distance as the objective function, and the Schuster periodogram as the reference sample. The effectiveness of the hybrid method has been experimentally evaluated on the basis of the author's software. It is shown that with the duration of the observation window no greater than 10 ms, the use of the hybrid method increases the accuracy of spectral analysis by more than 30%, compared to the well-known Berg method, the order of which is established according to the Akaike information criterion. [ABSTRACT FROM AUTHOR]

The article covers topical issues of organizing intensive training of artillery cadets in wartime based on the remote use of 3D simulators. In such an educational process, there is a need to coordinate dynamically the speed of developing detailed 3D models with the speed of information perception by cadets. The authors describe the process of information exchange in training system and they propose a mathematical model of information transmission. In addition, they offer a mathematical model of information perception by cadet and conduct a pedagogical experiment. Finally, they draw conclusions regarding the implementation of the developed models within the educational process. The results of the pedagogical experiment confirm theoretical formulations and make it possible to synchronize the speed of 3D models development with the speed of their study, considering the intensity of perception by cadets of a huge information volume within a short time. [ABSTRACT FROM AUTHOR]

The problem of the spectral analysis of speech signals in automatic speech recognition systems is considered within the framework of a dynamically developed direction of investigations in the field of acoustic measurements. We indicate that efficiency of the analyzed systems under unfavorable conditions of speech production (noise and insufficient intelligibility of speech sounds) is low as compared with human perception of oral speech. To improve the efficiency of automatic speech recognition systems, we propose to use a two-stage algorithm of spectral analysis of the speech signals. The first stage of processing of speech signals is their parametric spectral analysis performed by using an autoregressive model of the vocal tract of a conventional speaker. The second stage of processing is the transformation (modification) of the obtained spectral estimate according to the principle of frequency-selective amplification of the amplitude of main formants of the intraperiod power spectrum. The software implementation of the proposed algorithm is described on the basis of the computational procedure of fast Fourier transform. By using the software developed by the authors, we performed full-scale experiments and studied an additive mixture of vowel sounds in the speech of a control speaker with white Gaussian noise. The obtained experimental results enable us to conclude that the amplitudes of the main formants of speech signals are amplified by 10–20 dB and, hence, the intelligibility of speech sounds substantially improves. The developed algorithm can be used in the automatic speech recognition systems based on processing of the speech signals in the frequency domain, including the use of artificial neural networks. [ABSTRACT FROM AUTHOR]

The problem of determining the accuracy of an autoregressive model of a speech signal is considered, and a method for measuring the accuracy index in the sliding observation window mode is proposed. As an indicator of accuracy, we used a modified value of the COSH-distance (hyperbolic cosine) of the autoregressive model relative to the eponymous (single phoneme) Schuster periodogram as a reference spectral sample. To study the possibilities of the proposed method, a full-scale experiment was set up and carried out, in which the object of study was a set of autoregressive models of different orders. These models were obtained by Berg's method for the vowel speech sounds of a test speaker. According to the results of the performed measurements for each vowel, the optimal values of the autoregressive order and the corresponding optimal autoregressive model were found. It is shown that this optimization made it possible to increase the accuracy of the autoregressive model of the speech signal by more than 60%, depending on the sound of the test speaker's speech and the characteristics of his vocal tract. The results obtained are intended for use in automatic processing and digital speech transmission systems with radical data compression based on linear prediction coefficients. [ABSTRACT FROM AUTHOR]

The problem of determining a fundamental tone frequency of a speech signal in the presence of white Gaussian noise is examined. A method for measuring this frequency is proposed which takes into account the periodic structure of the power spectrum of voiced speech frames and is based on the principle of harmonic energy accumulation in the frequency domain. For this purpose a procedure for equalizing the envelope of the power spectrum is introduced in the algorithm for processing a speech signal using a two-level autoregression model of the observations: within the limits of a single period of the fundamental tone and within an interval of several of these periods. Here adaptation of the order of the autoregression of the lower level to the observed frame is planned. An example of the practical realization of the adaptive method based on the Berg method is examined. The basic advantages of the adaptive method compared to the known analogs are high speed and enhanced noise stability, which are confirmed in a full-scale experiment. A gain in threshold signals of 5-10 dB was obtained through use of the adaptive method. [ABSTRACT FROM AUTHOR]

The development of noncatalytic procedures for processing hydrocarbon gases is an important way to increase the efficiency of gas-chemical processes and decrease their power consumption. The paper deals with thermodynamic and kinetic modeling of noncatalytic processes of the partial oxidation and steam and carbon dioxide conversion of methane in the temperature interval 1400–1800 K and with analysis of the process for syngas production by matrix conversion of rich methane–oxygen mixtures. Comparison of the kinetic calculations with the experimental data demonstrated the possibility of applying published models to the description of the matrix conversion of methane. The possibility of developing a highly efficient technology based on noncatalytic partial oxidation of hydrocarbons for the syngas production without СО2 emission into the environment is discussed. [ABSTRACT FROM AUTHOR]

The interaction of two types of modality of a system for processing audiovisual information in the problem of evaluating the emotional state of users of dialogue information systems was studied. In order to enhance the precision of an estimation in real time, it is proposed to use an audio modality for the purpose of detecting speech segments of increased emotionality. As an indicator of the degree of speech emotionality, the intensity of the flow of vowel sounds in a user's speech signal at input to the information system is used. A method has been developed for measuring this indicator from the empirical probability of the occurrence of vowel sounds in the user's a speech signal. An example is presented for practical implementation of the method in soft real time. A full-scale experiment using the authors' software was posed and presented. The advantages of the proposed method are shown: high speed of operation and high sensitivity to the change in the level of speech emotionality of users. Results obtained are intended for developers of advanced information systems with an audiovisual user interface. [ABSTRACT FROM AUTHOR]

Two types of constitutive equations accounting for the stress mode and the loosening of the material during elastoplastic deformation are considered. The constitutive equations of one type include two nonlinear relationships between the first invariants of the stress and strain tensors and between the second invariants of the deviator tensors and include the third invariant of the stress deviator. The constitutive equations of the other type use equivalence stress containing the first and second invariants of the stress tensor. Literature experimental data for tubular isotropic specimens under tension, compression, torsion, and internal pressure are used for assessing the loosening of the material. [ABSTRACT FROM AUTHOR]

The article considers the problem of personal biometric data "aging" over time. A method has been proposed to overcome this problem by automatically updating the specified data in the biometric system storage using the speech signals of registered users obtained during latest requests for their identification and online service. The proposed method uses a scale-invariant indicator of the voice template quality. As a result, it is characterized by guaranteed reliability of the decisions made in the conditions of a wide speech signal dynamic range. It was established that the use of a scale-invariant indicator provides the guaranteed significance level of decisions made by a conventional observer. A full-scale experiment implementing the proposed method has been set up and carried out using an authoring software; practical justification for the effectiveness of the proposed method with real speech data has been given. The results obtained are intended for using in the development of new and modernization of existing systems and technologies for automated quality control and updating of personal biometric data. [ABSTRACT FROM AUTHOR]

A technique of numerical analysis of the elastoplastic axisymmetric stress–strain state of thin isotropic shells with different tensile and compressive properties under mechanical loading is described. The technique is based on constitutive equations of plasticity that include either the third invariant or mixed invariants of the stress deviator. To specify the constitutive equations, experimental data known from the literature and obtained in testing tubular iron specimens in tension, compression, and torsion are used. Numerical results are analyzed. [ABSTRACT FROM AUTHOR]

A method for the numerical analysis of the elastic and plastic stress–strain state of layered bodies of revolution made of isotropic and orthotropic materials is proposed. For isotropic materials, modified thermoradiation plasticity equations of deformation along trajectories of small curvature are used. The equations of elasticity are used to study the deformation of orthotropic materials. The dependence of the physical and mechanical properties of materials on temperature and radiation is taken into account. For the convenience of developing the algorithm, the relations between the components of the stress and strain tensors in an arbitrary element of the body are written in the form of a generalized Hooke's law for an orthotropic material with additional terms. The loading process is divided into a number of small stages. The components of the stress–strain state are determined at each stage using the method of successive approximations. As an example, the stress–strain state of a thin layered shell under thermomechanical loading and radiation exposure is considered. [ABSTRACT FROM AUTHOR]

Various options for designing the direct oxidation of natural gas to methanol are considered: flow-through, with a distributed supply of the oxidizer along the length of the reactor, and circulation. For each of the considered options for designing the process, the methanol yield was calculated, as well as the parameters at which the resulting blow-off gas can be used as a fuel. The optimal recycling rate in the circulation process has been determined. [ABSTRACT FROM AUTHOR]

The present paper discusses the problem of distortions in speech signals transmitted over a communication channel to a biometric system during voice-based remote identification. A possible rectification approach involves a preliminary correction of the frequency spectrum of the received signal based on the pre-distortion principle. Taking into account a priori uncertainty, a new information indicator of speech signal distortions is proposed, along with a method for its measurement under conditions of small observation samples. An example of fast practical implementation of the method based on a parametric spectral analysis algorithm is considered. Results of an experimental test of the proposed approach are provided for three different communication channel instantiations. It is shown that the proposed method facilitates the transformation of an initially distorted speech signal into compliance with a registered voice template using an acceptable algorithmic information discrimination criterion. The described approach may be used in existing biometric systems and speaker identification technologies. [ABSTRACT FROM AUTHOR]

Refactoring is an integral part of the modern software development process. Often, the refactoring must be performed at the global level with modifications in a large number of files. Making these modifications is a long and painstaking work. However, users rarely employ automated tools for this purpose because they consider them unreliable and difficult to use. In this paper, a new tool for transforming the source code is described. It is based on the intuitively clear specification of transformation rules in the form of short code fragments in C or C++. These rules describe the code before and after the transformation. We believe that, due to the absence of additional abstractions (such as domain-specific languages), this approach can be easily used in practice. Even though the tool uses source code templates, it operates on the level of the abstract syntax tree. This enables the tool to better analyze the code and verify the validity of transformations. [ABSTRACT FROM AUTHOR]

The article continues our previous work [V. V. Savchenko and A. V. Savchenko, Izmeritel'naya Tekhnika, No. 12, 46–52 (2019)]. We study the problem of automatic control of the quality of voice samples recorded and stored in the Unified Biometric System. We propose a solution of the problem of timely updates of the collected samples required because their consumer qualities are lost in the course of time. A new indicator of the acoustic quality of voice samples in the Kullback–Leibler information metric is investigated and a new procedure is proposed for measuring this indicator at the times of contact of the users with the system with service requests. An example of practical implementation of the proposed method in the real-time mode is demonstrated. By using software specially developed by the authors, we performed a full-scale experiment and obtained quantitative estimates of the period of updating of voice samples. Some recommendations concerning their practical application are given. The accumulated results can be used for the purposes of development of new systems and technologies (and upgrading of the existing systems) of automatic quality control and adaptive renewal of the biometric personal data samples. [ABSTRACT FROM AUTHOR]

The problem of automated quality control of audio recordings containing voice samples of individuals is considered. It is shown that in solving this problem the most acute impediment is the problem of small samples of observations. To overcome the problem, a new, high-speed method of acoustic measurements is proposed, based on the principle of relative stability of the frequency of the fundamental tone of a speech signal within a voice sample of short duration. An example of practical implementation of the developed method according to a scheme with inter-period signal accumulation is considered. Using proprietary software, a full-scale experiment was conducted in which statistical estimates of the effectiveness of the method in noise conditions were obtained. It is shown that when using the proposed method, if the signal-to-noise ratio is lower than 15 dB, an audio recording is rejected with a probability of 0.95 or more as unsuitable for biometric identification of a person. The results obtained are intended for use in the development of new systems and modernization of existing systems and technologies for collection and automated quality control of biometric personal data. The article is intended for a wide circle of specialists in the field of acoustic measurements and digital processing of speech signals, as well as for practitioners who organize the work of authorized organizations in preparing samples of biometric personal data for registration with the unified biometric system (UBS). [ABSTRACT FROM AUTHOR]

We consider the problem of determination of the intelligibility of speech of a speaker according to a finite fragment of the speech signal. It is shown that the main difficulties in the solution of this problem are connected with the necessity of analysis of small samples. To overcome the problem of small samples, we proposed a new high-speed method for measuring the intelligibility of speech signals on the sonic level of its perception. The proposed method is based on the information indicator of speech intelligibility in the Kullback-Leibler metric. We consider an example of practical realization of the new method with the use of a self-regression model of minimum sound units from the speech flow of a speaker. The characteristics of efficiency of the new method are analyzed. It is shown that, under certain conditions, the application of the information indicator enables us to realize the general systems principle of guaranteed result. On the basis of the software developed by the authors, we designed and performed full-scale experiments and established quantitative estimates for the speed of this method. It is shown that, with the help of this method, quite accurate and reliable estimates of the information indicator are obtained for short (2–3 min) segments of speech signals. The accumulated results and the conclusions made on their basis are intended for applications in the development of new systems and improvement of the existing systems of automatic speech processing and recognition intended for the operation in the real-time mode. [ABSTRACT FROM AUTHOR]

A method for numerical analysis of the thermoelastoplastic axisymmetric stress–strain state of thin isotropic shells undergoing mechanical loading and radiation exposure is outlined. The modified constitutive equations of thermoplasticity describing inelastic deformation along small-curvature paths are employed. The thermoelastoplastic state of a shell in the form of a spherical segment is analyzed numerically with allowance for the effect of radiation. [ABSTRACT FROM AUTHOR]

The nonaxisymmetric elastoplastic stress–strain state of bodies of revolution under nonisothermal combined loading is analyzed with allowance for secondary plastic strains. The study is based on the use of the constitutive equations of the theory of small-curvature processes and finite-element method. The model of elastic unloading of a material with perfect Bauschinger effect and isotropic hardening is employed. Numerical examples illustrate how the choice of an unloading model affects the results obtained. [ABSTRACT FROM AUTHOR]

We developed a new method for measuring the pitch frequency of speech signals with elevated noise immunity. The problem of protection against intense background noise is solved in this method by the frequency selection of vocalized segments of speech signals according to a scheme with comb filter of interperiodic accumulation. The efficiency of the method is analyzed both theoretically and experimentally with the help of a multichannel frequency meter intended for the acoustic speech analysis. It is shown that, for a signal-to-noise ratio of 10 dB and higher, the error of the method does not exceed 2%. [ABSTRACT FROM AUTHOR]

Equilibrium distribution of oxidation products was calculated for the system СН4 + ψО2 → products at 0.5 < ψ < 1.0 and temperature of 900-1700 K, with the existence of phase transitions in the system taken into account. Two regions are conditionally distinguished: I, at ψ > 0.6 and temperatures higher than 1000-1200 K (depending on ψ), when there is no Csolid in the system; and II, if this component is present in the system. The range of working temperatures and values of ψ, at which the matrix conversion process occurs, falls within region I. A nearly 100% conversion of oxygen and methane is reached within this region; there is no Csolid; and CO, H2, CO2, and H2O are products of the partial oxidation of methane in equilibrium. The temperature limits within which the system passes into region II and the formation of the synthesis gas is accompanied by the appearance of soot were determined. Formulas describing the dependence of the yield of oxidation products per mole of converted methane at various ratios between the methane and oxygen concentrations were derived. An expression was obtained on the basis of experimental data, which can be used to approximately calculate to within <6% the most important technological parameter of the matrix conversion process, [H2]/[CO] ratio. [ABSTRACT FROM AUTHOR]

A technique of describing the damage of deformable inelastic isotropic and elastic orthotropic materials in studying the thermoelastoplastic stress-strain state of compound bodies of revolution under nonaxisymmetrical loading and heating is proposed. The numerical results are plotted and analyzed. [ABSTRACT FROM AUTHOR]

A new method is proposed for measurements of an index of acoustic voice quality using the Kulbaka-Leybler information metric. The primary benefit of this method consists in its high-level dynamic properties, as calculated by eliminating the problem of a small number of observational samples. A theoretical study of the method’s efficiency was conducted, and its conclusions were confirmed experimentally. It has been established that, in order to provide a sufficiently precise assessment of the voice quality of the speaker, a speech signal of duration 2-3 minutes is required. [ABSTRACT FROM AUTHOR]

A method for numerical analysis of the elastoplastic axisymmetric stress-strain state of thin shells undergoing nonisothermal deformation along paths of small curvature with allowance for secondary plastic strains and the third invariant of stress deviator is elaborated. The stress-strain state of a shell during heating and cooling is analyzed numerically. [ABSTRACT FROM AUTHOR]

An algorithm for numerical analysis of the elastoplastic stress-strain state of thin shells that deform along small-curvature paths under axisymmetric nonisothermal loading is developed. Repeated plastic strains are taken into account. The stress-strain state of a shell during heating and cooling is numerically analyzed. [ABSTRACT FROM AUTHOR]

During the first observing run of LIGO, two gravitational wave events and one lower-significance trigger (LVT151012) were reported by the LIGO/Virgo collaboration. At the time of LVT151012, the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) was pointing at a region of the sky coincident with the high localization probability area of the event and thus permitted us to search for its electromagnetic counterpart (both prompt and afterglow emission). The imaging instruments on board INTEGRAL (IBIS/ISGRI, IBIS/PICsIT, SPI, and the two JEM-X modules) have been exploited to attempt the detection of any electromagnetic emission associated with LVT151012 over three decades in energy (from 3 keV to 8 MeV). The omni-directional instruments on board the satellite, i.e., the SPI-ACS and the IBIS/Veto, complemented the capabilities of the IBIS/ISGRI and IBIS/PICsIT for detections outside their imaging field of view in order to provide an efficient monitoring of the entire LVT151012 localization region at energies above 75 keV. We did not find any significant transient source that was spatially and/or temporally coincident with LVT151012, obtaining tight upper limits on the associated hard X-ray and γ-ray radiation. For typical spectral models, the upper limits on the fluence of the emission from any 1 s counterpart of LVT151012 ranges from Fγ = 3.5 × 10-8 erg cm-2 (20–200 keV), within the field of view of the imaging instruments, to Fγ = 7.1 × 10-7 erg cm-2 (75–2000 keV), considering the least favorable location of the counterpart for a detection by the omni-directional instruments. These results can be interpreted as a tight constraint on the ratio of the isotropic equivalent energy released in the electromagnetic emission to the total energy of the gravitational waves: E75−2000 keV/EGW< 4.4 × 10-5. Finally, we provide an exhaustive summary of the capabilities of all instruments on board INTEGRAL to hunt for γ-ray counterparts of gravitational wave events, exploiting both serendipitous and pointed follow-up observations. This will serve as a reference for all future searches. [ABSTRACT FROM AUTHOR]

A method for numerical analysis of the thermal elastoplastic axisymmetric stress-strain state of thin layered shells made of isotropic and transversely isotropic materials subject to thermal and mechanical loading and radiation exposure is proposed. The constitutive equations of isotropic thermoplasticity and transversely isotropic elasticity are used. The elastoplastic state of a two-layer plate subject to radiation exposure is determined and analyzed. [ABSTRACT FROM AUTHOR]

Graphs of the normalized power spectrum estimation (5) of the speech sound signal "a" at the output of the flattening filter (4) with order I p i = 32 of the autoregression model. The equation should read 3 HT ht Graph The caption for Fig. [Extracted from the article]

The matrix conversion of natural gas into synthesis gas, in which the autothermal oxidation occurs in the surface combustion mode in a cavity of a closed three-dimensional matrix made of a gas-permeable material, was studied experimentally. The specific volumetric productivity of such converters considerably exceeds that of traditional types of converters and allows conversion of hydrocarbon gases of virtually any composition into synthesis gas. Prospects for practical use of the new type of converters are discussed. [ABSTRACT FROM AUTHOR]

Methods and results of studying the three-dimensional viscoplastic stress-strain state of engineering structures under thermomechanical loading are presented. The following classes of thermoviscoelastic problems are considered: axisymmetric problems, nonaxisymmetric problems for bodies of revolution, three-dimensional problems for arbitrarily shaped bodies, three-dimensional problems for isotropic and anisotropic bodies of revolution [ABSTRACT FROM AUTHOR]

Reducing carbon dioxide emissions during production is one of the main trends in modern oil and gas chemistry. One of the most realistic possibilities for achieving this is to involve carbon dioxide generated in technological processes as a feedstock for producing gas chemical products. The maximum effect can be achieved in the production of large-scale chemicals, such as syngas, hydrogen, and methanol. We consider such possibilities and present a new combined autothermal process for the joint production of hydrogen and methanol based on non-catalytic matrix conversion of natural gas into syngas, which allows one to almost avoid CO2 emissions. [ABSTRACT FROM AUTHOR]

We consider the issue of small observation samples in the problem of spectral analysis of the random time series. It is proposed to solve the considered problem using the information-theoretic approach and a new algorithm based on the principle of minimum divergence of the cognominal spectral estimates yielded by the results of several independent observations in the Kullback-Leibler information metric. An example of a practical realization of the algorithm is considered and its asymptotic properties are studied. [ABSTRACT FROM AUTHOR]

Magnetic transitions and Bose-Einstein condensation (BEC) are studied in a self-consistent field model, analogous to the model of a molecular field in the theory of ferromagnetism. It is shown that the present model is internally consistent and suitable for description at any value of a dimensionless parameter characterizing the system. Different possible types of phase transitions, at which magnetization and BEC density emerge either continuously or discontinuously, are considered. Critical values of the phenomenological parameter, at which the character of phase transitions changes, are calculated. The phase diagram in temperature-particle number density coordinates is plotted. [ABSTRACT FROM AUTHOR]

We have analyzed experimental kinetic data for nitro compound consumption, for the formation of the corresponding amino product, and for the accumulation of intermediate products and by-products in the hydrogenation of chlorine-containing aromatic nitro compounds. The reaction has been carried out under static conditions over a platinum catalyst on a porous support in the presence of pyridine. The effect of the admixture on different hydrogenation steps of a chlorine-containing aromatic nitro compound has been quantitatively interpreted. [ABSTRACT FROM AUTHOR]

A model for the cooperation of autonomous agents of a multiagent system based on self-coordination is developed. A method is proposed to set up controls for each agent based on Kirchhoff matrices, sets of mutual-position vectors, and combined attraction-repulsion potential functions. The proposed approach was modeled for the formation of a multiagent system structure with desired topology. [ABSTRACT FROM AUTHOR]

Aims. We study timing properties of a large sample of gamma-ray bursts (GRB) detected by the anti-coincidence shield (ACS) of the SPI spectrometer of INTEGRAL telescope. Methods. We identify GRB-like events in the SPI-ACS data. The data set under investigation is the history of count rate of the SPI-ACS detector recorded with a binning of 50 ms over the time span of ∼10 yr. In spite of the fact that SPI-ACS does not have imaging capability, it provides high statistics signal for each GRB event, because of its large effective area. Results. We classify all isolated excesses in the SPI-ACS count rate into three types: short spikes produced by cosmic rays, GRBs and Solar flare induced events. We find some ∼1500 GRB-like events in the 10 yr exposure. A significant fraction of the GRB-like events identified in SPI-ACS occur in coincidence with triggers of other gamma-ray telescopes and could be considered as confirmed GRBs. We study the distribution of durations of the GRBs detected by SPI-ACS and find that the peak of the distribution of long GRBs is at ≃20 s, i.e. somewhat shorter than for the long GRBs detected by BATSE. Contrary to the BATSE observation, the population of short GRBs does not have any characteristic timescale. Instead, the distribution of durations extends as a powerlaw to the shortest timescale accessible for SPI-ACS, ≤50 ms. We also find that a large fraction of long GRBs has a characteristic variability timescale of the order of 1 s. We discuss the possible origin of this timescale. [ABSTRACT FROM AUTHOR]

The technique for determination of zero-strength temperature, Tz.s, and zeroductility temperature, Tz.d, is developed and tested with the goal of evaluation of processes, which take place in dispersion-strengthened nickel alloys and in the welded joints of these alloys at temperatures close to the melting temperature point TL. Analysis of changes in tensile strength, σB, at temperatures close to TL shows the presence of an inflection on the strength curve for alloys with both monocrystalline and polycrystalline structures. The temperature of this inflection coincides with the temperature of the sharp fali of relative reduction in area, ψ, to almost zero which indicates the start of melting of cast metal. These suppositions are confirmed by fractographic and metallographic investigations of the structure and fracture surface. [ABSTRACT FROM AUTHOR]

We study time-resolved spectra of the prompt emission of Swiftγ-ray bursts (GRB). Our goal is to see if previous BATSE claims of the existence of a large amount of spectra with the low-energy photon indices harder than 2/3 are consistent with Swift data. We perform a systematic search of the episodes of the spectral hardening down to the photon indices in the prompt emission spectra of Swift GRBs. We show that the data of the Burst Alert Telescope (BAT) instrument on board of Swift are consistent with BATSE data, if one takes into account differences between the two instruments. Much lower statistics of the very hard spectra in Swift GRBs are explained by the smaller field of view and narrower energy band of the BAT telescope. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel simple method, based on an implementation of space mapping technique, for improvement of the quality of tetrahedral and hexahedral meshes. The same approach is used for surface meshes where geometry of the initial surface mesh is preserved by a local mesh improvement such that new positions of the interior nodes of the mesh remain on the original discrete surface. The proposed method can be used in the pre-processing stage for subsequent studies (finite element analysis, computer graphics, etc.) by providing better input parameters for these processes. Experimental results are included to demonstrate the functionality of our method. [ABSTRACT FROM AUTHOR]

Causes of fracture of the martensitic-ferritic steel blades of the variable inlet guide vane for an axial-flow compressor of the gas pumping unit GTK-25I have been studied. There are several stages of blade fracture: corrosion, fatigue, and fracture. At the initial state, corrosion damage occurs at the martensite-ferrite interface, which is followed by intragranular corrosion damage along martensite needles and fatigue failure within the grain bodies. [ABSTRACT FROM AUTHOR]

The paper proposes a method to allow for the stress mode in analyzing the thermoelastoplastic stress-strain state of compound bodies of revolution under asymmetric loading and heating. Use is made of a semianalytic finite-element method and the method of successive approximations. Some numerical results are presented [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the diagnostic interest of Hector Battifora mesothelial antigen-1 (HBME-1), thyroid peroxidase (TPO), and dipeptidyl aminopeptidase IV (DPP4) in thyroid fine-needle aspirates obtained from 200 resected thyroid lesions (55 colloid nodules, 54 follicular adenomas, 59 papillary cancers, and 32 follicular carcinomas). Hector Battifora mesothelial antigen-1 or TPO expression (% positive cells) and DPP4 staining score (12-point scale) were evaluated. Receiver operating characteristic (ROC) curves were plotted and optimal cutoff values for diagnosing malignancy were determined. The TPO ROC curve was consistently higher than the HBME-1 ROC curve. The TPO curve was also higher than the DPP4 curve with regard to sensitivity, but dipped below the DPP4 curve with regard to specificity. Using a cutoff value of <80% positive cells for TPO, >10% positive cells for HBME-1, and staining score > or =1 for DPP4, sensitivity to specificity ratios were 98-83% for TPO, 90-60% for HBME-1, and 88-80% for DPP4. Two particularly interesting findings of this study were the low negative likelihood ratio of TPO (0.02) allowing highly reliable exclusion of malignancy and the 100% specificity of DPP4 staining scores=12. Due to poor performance on follicular lesions, HBME-1 showed no advantage over TPO or DPP4. [ABSTRACT FROM AUTHOR]

A technique is proposed to allow for damages and different tensile and compressive moduli of orthotropic materials in stress-strain analysis of compound bodies of revolution under nonaxisymmetric loading and heating. The technique combines the semi-analytic finite-element method and the method of successive approximations [ABSTRACT FROM AUTHOR]

The formation of LaSrNiO4-and LaSrScO4-based solid solutions with the general stoichiometry LaSrNi1 − x ScxO4 (0 < x < 1) has been studied in air at temperatures from 700 to 1300°C. According to x-ray diffraction results, the former solid solutions exist in the composition range 0 < x ≤ 0.2. Their lattice parameters have been determined, and their resistivity and thermoelectric power have been measured as functions of temperature. Oxygen release and absorption measurements at temperatures from 20 to 1000°C and oxygen partial pressures from 2 to 330 Pa suggest that the presence of scandium has a stabilizing effect on the oxygen sublattice of the solid solutions. The possible mechanisms of this effect are discussed. [ABSTRACT FROM AUTHOR]