bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and photocatalytic degradation of rhodamine B using ternary zeolite/WO3/Fe3O4 composite
Authors: Rubab Maham , Bhatti Ijaz Ahmad , Nadeem Nimra , Shah Syed Ali Raza , Yaseen Muhammad , Naz Muhammad Yasin , Zahid Muhammad 
Published: May 2021

Abstract
Demand for freshwater increases day by day as impurity increases due to the industrial, domestic and municipal waste in the water. Inappropriate disposal of coal fly ash (CFA) is not eco-friendly, therefore the need is to convert it into some beneficial material like zeolite. Zeolite-based composites with metal oxides show high cation interchange capacity, fast adsorption, and high efficiency for the removal of wastewater pollutants. In this research work, metal oxide along with zeolite (derived for CFA) was prepared. Metal oxide (WO3) and magnetite (Fe3O4) based zeolite composite was used adsorption enhanced photocatalytic degradation of rhodamine B dye. Ternary composite (zeolite/WO3/Fe3O4) was characterized using a scanning electron microscope, x-ray diffraction, Fourier transform infrared spectroscopy. The bandgap energy of composite was estimated using Tauc plot method from the data obtained after UV–visible spectroscopy. The behavior of composite under acidic and basic conditions was analyzed using pHpzc of the composite. Influencing parameters like pH, dye concentration, contact time, and catalyst dosage was optimized under ultraviolet irradiations (254 nm). The results show that maximum degradation was achieved with zeolite/WO3/Fe3O4 composite under optimized conditions of pH = 7, catalyst dosage = 10 mg/100 ml, RhB concentration 10 ppm, and time 60 min. The first-order kinetic model was best fitted to the experimental data. RSM was used as a statistical tool to analyze the data.
Integrated thermoacoustic and ultrasound imaging based on the combination of a hollow concave transducer array and a linear transducer array
Authors: Wang Xue , Huang Lin , Chi Zihui , Jiang Huabei 
Published: May 2021

Abstract
To integrate the high resolution of ultrasound imaging (UI) and the high tissue specificity of thermoacoustic imaging (TAI) and to achieve an easy and precise co-registration of the two different imaging modalities, we present and demonstrate a hybrid thermoacoustic and ultrasound (TA/US) imaging system based on the combination of a novel hollow concave array and a commercial linear array. This TA/US imaging system can provide enhanced imaging of both tissues’ mechanical and dielectric properties. We verified the effective imaging performance of the hybrid TA/US system using tissue phantom experiments. In vivo TA/US imaging of the wrist and foot in healthy volunteers was also demonstrated using the hybrid system. This hollow concave array provided enhanced imaging performance for TAI because of its wide angular coverage with an optimal center frequency, showing a large effective imaging field of view (FOV) and improved images with high contrast and superior quality. Compared with stand-alone UI or TAI, the hybrid TA/US imaging presented more complete tissue anatomical structures, like skin, muscles, tendons, blood vessels, and bones for possible human disease diagnosis, although the US image quality using the hybrid system was slightly lower because the distance between the tissue and commercial ultrasound array was not ideal. This study suggests that the hybrid TA/US imaging approach has the potential to become a clinical tool for diagnosis of diseases in the wrist and foot.
Superconducting single-photon detector with a system efficiency of 93% operated in a 2.4 K space-application-compatible cryocooler
Authors: Hu Peng , Ma Yuexue , Li Hao , Liu Ziyao , Yu Huiqin , Quan Jia , Xiao You , You Lixing , Liu Yanjie , Liang Jingtao , Wang Zhen 
Published: May 2021

Abstract
We report herein the development of a superconducting nanowire single-photon detector (SNSPD) that uses a hybrid cryocooler compatible with space applications. The hybrid cryocooler incorporates a two-stage high-frequency pulse-tube cryocooler and a Joule–Thomson loop, which produces a minimum temperature of 2.2 K. The SNSPD with the structure of sandwiched nanowires integrated in the cryocooler shows a maximum detection efficiency of 93% at 1550 nm, which makes it promising for deep-space communications and quantum information applications.
Numerical modeling and simulation for laser beam welding of ultrafine-grained aluminium
Authors: Lazov Lyubomir , Teirumnieks Edmunds , Draganov Ivo , Angelov Nikolay 
Published: May 2021

Abstract
Laser beam welding of aluminium offers huge potential for a wide variety of welding of different thickness parts with the method of thermal conductivity due to the relatively high difference between melting temperature and evaporation. However, due to the high melting temperature and good thermal conductivity of this light metal, the temperature gradients during the welding process are usually high, causing residual stresses in the weld, which can lead to undesirable deterioration of the weld pool properties and the quality of the process. Physical modelling and simulations of the laser welding process are powerful tools for gaining a fundamental understanding of the technological process. They are also a suitable tool for preliminary assessment of the intervals in which the real preliminary experiments for process optimization should take place. This work is devoted to the numerical modelling of the process of welding ultrafine-grained aluminium using a fibre laser. A three-dimensional model of the welding process was created, using the finite element method implemented in the program ABAQUS. The temperature fields at depth z and on the surface x, y in the welded samples is determined. The temperature change as a function of time for different coordinates of the weld is also analysed. During numerical calculations, the power, machining speed and diameter of the workplace are variable. The obtained results are compared with real experiments conducted in the laboratory by other researchers.
Multicolor optomechanically induced transparency in a distant nano-electro-optomechanical system assisted by two-level atomic ensemble
Authors: Pan Guixia , Xiao Ruijie , Chen Huajun , Gao Juan 
Published: May 2021

Abstract
We investigate the multicolor optomechanically induced transparency (OMIT) of a nano-electro-optomechanical system with two-level atomic ensemble. The system consists of two distant cavities and two charged mechanical resonators coupled via the Coulomb interaction. The focus of our study is on the number of the OMIT windows, which can be manipulated by the coupling strength between the system components. Also, the four transparency windows can be observed from the output probe field. When some coupling strengths disappear, the number of transparent windows decreases. Furthermore, the number and the width of the transparent windows can be controlled by the coherent interactions between the optical mode and the mechanical mode, or between the optical mode and the atoms, or between the two optical modes, or controlled by the Coulomb coupling between the two charged mechanical modes. Our approach is feasible for phonon storage, which will have the great potential applications for quantum information processing.
The binding of bovine serum albumin with dye molecules at different pH values. Fluorescence lifetime studies
Authors: Gorodnichev E S , Kuleshova A A , Volkova O I , Saletsky A M 
Published: May 2021

Abstract
The spectral and kinetic characteristics of the fluorescence of the solutions of bovine serum albumin (BSA) and the dyes (N-(p-carboxyphenyl) imide of 4-(dimethylamino) naphthalic acid (CAPIDAN) and Bengal Rose (BR)) in BSA solutions were studied at 3.5 < pH < 8.0. It was discovered that the attenuation of CAPIDAN fluorescence at the studied pH region is described by the sum of three components (with the values of time constants: 6.0 ns < τ
1 < 8.5 ns, 1.8 ns < τ
2 < 2.2 ns, 0.4 ns < τ
3 < 0.6 ns), while it is described by two components for BR (0.33 ns < τ
1 < 0.4 ns, 2.0 ns < τ
2 < 3.1 ns). It is shown that the mechanisms of the binding of dye and protein molecules are different for CAPIDAN and BR. The binding process of CAPIDAN and BSA is regulated by the conformation of the binding center. The interaction between the BR and BSA molecules is electrostatic, the magnitude of this interaction is determined by the ratio of the charges of the dye and protein molecules. The dependence of the wavelength of the maximum of the spectra, the intensity of the glow and the efficiency of quenching of the fluorescence of the molecules of the studied dyes on the pH is analyzed. The parameters dμ, which characterizes the change in the dipole moment of the fluorophore during its excitation, and η, which characterizes the change in the intensity at the maximum of the fluorescence spectrum at different pH solutions, were also determined for BR. The following ratios were determined at the studied pH range:

d
μ
>
1

and η < 1. The changes of the characteristics of the stationary fluorescence of the studied dyes at different pH of BSA solutions confirm the mechanisms of the binding between CAPIDAN or BR molecules and protein molecules.
Design of the cryogenic system of the wideband phased array feed for QTT
Authors: Ma Jun , Wu Yang , Xiao Song , Niu Sheng-Pu , Wang Kai 
Published: May 2021

Abstract
Phased array feeds (PAFs), which illuminate the dish with digitally synthesized beams instead of separated horns, provide the capability for wider and continuous field-of-view surveys. As a promising technology for next generation radio telescopes, PAFs will provide the Qi Tai Telescope (QTT), which will be next world-class fully steerable radio telescope, an opportunity of reaching several cutting-edge science goals. This paper presents a brief introduction of the wideband PAF for QTT, and the detailed design and simulation of the cryogenic system. Based on this design, a scaled prototype of the spherical vacuum window, which is the key part of the cryogenic system, has been built and the performance is verified.
Precision of the Chinese Space Station Telescope (CSST) stellar radial velocities
Authors: Sun Yang , Deng Ding-Shan , Yuan Hai-Bo 
Published: May 2021

Abstract
The Chinese Space Station Telescope (CSST) spectroscopic survey plans to deliver high-quality low-resolution (R > 200) slitless spectra for hundreds of millions of targets down to a limiting magnitude of about 21 mag, covering a large survey area (17 500 deg2) and a wide wavelength range (255–1000 nm by three bands GU, GV, and GI). In this work, we use empirical spectra of the Next Generation Spectral Library to simulate the CSST stellar spectra at R = 250, and investigate their capabilities in measuring radial velocities. We find that velocity uncertainties depend strongly on effective temperature, weakly on metallicity for only FGK stars, and hardly on surface gravity. It is possible to deliver stellar radial velocities to a precision of about 3 km s−1 for AFGKM stars, and about 10 km s−1 for OB stars, at signal-to-noise ratio (SNR) of 100. Velocity uncertainties using single GU/GV/GI band spectra are also explored. Given the same SNR, the GU band performs best, the GV band the second best, and then the GI band. The effects of spectral normalization and the imperfect template on velocity measurements are investigated and found to be very weak. The uncertainties caused by wavelength calibration are considered and found to be moderate. Given the possible precision of radial velocities, the CSST spectroscopic survey can enable interesting science such as searching for hyper-velocity stars. Limitations of our results are also discussed.
Proactive Management of Information Processes in the Industrial Internet
Authors: Sokolov B.V. , Potryasaev S.A. , Yusupov R.M. 
Published: May 2021

Abstract
The paper presents the scientific and practical foundations of the developed applied theory of proactive control of information processes in the industrial Internet based on cloud and fog computing. The main scientific contribution of the research results is that modern informatics, thanks to the developed theory, is enriched with the methodology and methodological support developed in classical cybernetics and neocybernetics. The paper shows the main elements of this theory, analyzes the possible ways of its development and practical use.
Optimal Estimation Using Deep Neural Networks Applied to Navigation and Motion Control
Authors: Amosov O.S. , Amosova S.G. 
Published: May 2021

Abstract
The critical analysis is given concerning the current state of using deep neural networks with convolutional and recurrent layers, a recurrent network of Long Short-Term Memory, Gated Recurrent Units for estimation tasks in relation to navigation and motion control. A comparison of neural network and traditional methods is given for understanding and explaining their functioning. The differences, advantages and disadvantages of deep neural networks in relation to solving estimation problems are revealed. The possibility of machine training with reinforcement is analyzed for estimation tasks in navigation and motion control in real time. The prospects of using neural networks in the processing of navigation data, as well as for the tasks of adaptive estimation and trajectory tracking, are formulated.
State observers as a means for estimating derivatives of deterministic signals
Authors: Kokunko Yu.G. , Antipov A.S. , Krasnova S.A. 
Published: May 2021

Abstract
To estimate the derivatives of a deterministic signal arriving in real time, a state observer is introduced, built as a replica of the virtual canonical model with an unknown bounded input. The results of a comparative analysis of observers with linear and piecewise linear corrective actions are presented, which are confirmed by the results of numerical modeling for piecewise differentiable composite function. Its derivatives have jump discontinuity points at the moments when the form of the function changes. It is shown that at these moments the observer variables with linear corrective actions with high gains have large surges, which increase by an order of magnitude with an increase in the order of the estimated derivative. Observers with bounded piecewise linear corrective actions do not have these problems and are recommended for use in practical applications.
Comparing underwater vehicle positioning algorithms using single-beacon navigation
Authors: Toropov A. B. , Loparev A. V. , Pelevin A. E. 
Published: May 2021

Abstract
Comparative analysis of two algorithms for underwater vehicle positioning using measurements of range to a drifting buoy and radial velocity is carried out. The algorithms based on building location contours and polynomial filtering are considered. Invalid data rate and radial RMS position error are analyzed to compare the algorithms. Based on the analysis made, the polynomial filtering algorithm is accepted as preferable.
Delay-compensating visual positioning of the mobile robot
Authors: Sevostyanov R.A. 
Published: May 2021

Abstract
The paper considers the task of the automatic positioning of the mobile robot in front of the external visual marker in the case of the presence of the transport delay in the control channel. As a basic regulator without the delay compensation we use mixed approach based on the visual servoing method and a special multipurpose control structure which is capable of taking into account a set of requirements to the controlled dynamics. To compensate the delay we apply the modification of the basic regulator which keeps the original transfer matrix. We also demonstrate the efficiency of the proposed approach by the results of the experiments with the computer model.
Optimal control in the New Keynesian model with monetary and fiscal policy interactions
Authors: Alexeeva T A , Kuznetsov N V , Mokaev T N , Polshchikova I A 
Published: May 2021

Abstract
Dynamics of the New Keynesian model in continuous time with the Rotemberg pricing mechanism is considered within a framework of an optimal control problem. Various regimes of monetary and fiscal policy (‘active’ and ‘passive’) can lead to unstable dynamics in the economy. Parameters of the Taylor rules for both monetary and fiscal policies determine conditions for local equilibrium determinacy. Mapping out the ranges of the Taylor coefficient values where local determinacy cannot be obtained allows to control the economic system by controlling these parameters.
Asymptotic behavior of second-order multiagent systems with fixed configuration
Authors: Agaev R.P. 
Published: May 2021

Abstract
Second-order protocols for consensus and convergence of agent’s trajectories to a fixed configuration are investigated. It is proved that the asymptotic behavior of the second-order system is uniquely determined by the eigenprojection of the Laplacian matrix of the communication digraph. The presented protocol and the corresponding expression for the asymptotic behavior are generalizations of the protocols for simpler cases.
Optimization of the manned aircraft pitch angle control loop with actuator rate limitation and nonlinear correction
Authors: Zaitceva Iuliia , Andrievsky Boris 
Published: May 2021

Abstract
In the paper a flight control system for a piloted aircraft on the pitch angle is considered, taking into account the rate saturation of the aircraft controlling surface. To prevent occurrence of the non-linear pilot-involved oscillations (PIO), a nonlinear correcting device is introduced into the control loop. On the basis of the pilot’s adaptation to control tasks variations, his/her mathematical model parameters are optimized and the choice of the nonlinear correcting device parameters is proposed. The sensitivity functions of the non-linear system are calculated for harmonic and square-wave reference signals. The results of the optimized system simulations are presented demonstrating good performance of the closed-loop system with nonlinear correction.
The development of Lyapunov direct method in application to synchronization systems
Authors: Smirnova Vera B , Proskurnikov Anton V , Utina Natalia V 
Published: May 2021

Abstract
The paper is devoted to asymptotic behavior of synchronization systems, i.e. Lur’e–type systems with periodic nonlinearities and infinite sets of equilibrum. This class of systems can not be efficiently investigated by standard Lyapunov functions. That is why for synchronization systems several new methods have been elaborated in the framework of Lyapunov direct method. Two of them: the method of periodic Lyapunov functions and the nonlocal reduction method, proved to be rather efficient. In this paper we combine these two methods and the Kalman-Yakubovich-Popov lemma to obtain new frequency–algebraic criteria ensuring Lagrange stability and the convergence of solutions.
Boundedness Condition for Anisotropic Norm of Linear Discrete Time-invariant Systems with Multiplicative Noise
Authors: Kustov A.Yu. , Timin V.N. , Yurchenkov A.V. 
Published: May 2021

Abstract
In this paper, the anisotropy-based analysis problem for the linear discrete time-invariant system with state-multiplicative noises is considered. The mean anisotropy of stationary input sequence is assumed to be bounded by given nonnegative value. For this setting, the boundedness condition for anisotropic norm of the system is obtained in terms of Riccati equations.
On a Mathematical Model of the Second-Order Measuring Transducer
Authors: Zamyshlyaeva A. A. , Bychkov E. V. , Tsyplenkova O. N. , Sviridyuk G. A. 
Published: May 2021

Abstract
The paper discusses a mathematical model of the second-order measuring transducer, which is based on the Lagrange equation of the second kind. On the basis of the theory of high-order Sobolev-type equations and optimal control of solutions to the Showalter – Sidorov problem, a theorem on the existence of an optimal dynamic measurement is obtained. Second-order sensors such as accelerometers, two-link oscillators and some other systems can be investigated in the framework of this mathematical model.
Optimal measurement problem for semi-linear descriptor system with Showalter–Sidorov condition
Authors: Gavrilova O. V. , Manakova N. A. , Perevozchikova K. V. , Sviridyuk G. A. 
Published: May 2021

Abstract
A semilinear descriptor system with a linear part and a nonlinear term is considered. This system is not resolved with respect to the derivative of the desired vector function. The article describes the optimal measurement problem for the model under study with the Showalter–Sidorov condition. Based on the methods of the theory of dynamic measurements, sufficient conditions for the existence of a solution to the problem of optimal measurement are found.
Convergence of the spline method for solving the optimal dynamic measurement problem
Authors: Keller A.V. , Sagadeeva M.A. 
Published: May 2021

Abstract
The problem of optimal dynamic measurement consists in finding the dynamically distorted input signal by observing the output signal. This problem is solved as an optimal control problem to minimize the difference between the values obtained from the output data and the model values obtained in the course of a computational experiment. It was shown earlier that this problem has a unique solution. For a complex form of the input signal, various numerical methods can be used to find the optimal dynamic measurement. This article suggests to use the spline method in order to solve this problem. Namely, we present the algorithm of this method and show that the solution obtained by the spline method converges to the exact solution of this problem.
Adaptive Control of Rigid Multi-Degree-of-Freedom Nonlinear Mechanical Plants
Authors: Quang Le Hong , Putov V. V. , Sheludko V. N. 
Published: May 2021

Abstract
The paper considers the problems of control synthesis of a rigid multi-degree-of-freedom (multi-DOF) nonlinear mechanical plant under conditions of parametric and functional uncertainty. Developed and investigated adaptive robust control systems are synthesized on the basis of three approaches: based on the method of computed torque, the method of majorizing functions, and also the method of integrator backstepping with modified adaptation algorithms with parametric projection. The results of a comparative study by modeling the designed adaptive systems for the nonlinear mathematical model of a four-degree manipulation arm described by the Lagrange equations are shown.
Extraction of isomorphic subformulas as a tool for logic ontology construction
Authors: Kosovskaya T. 
Published: May 2021

Abstract
A way of constructing a logic ontology for complex structured objects is considered in the paper. The descriptions of such objects are given in the predicate calculus language. An algorithm for extracting subsets of objects with the same properties and establishing their relative position is described. To construct such an ontology, an algorithm for extracting the largest subformula isomorphic to subformulas of all descriptions of objects from the class is used.