The study of melting process of the new plugging material at thermomechanical isolation technology of permeable horizons of mine opening

The article presents the results of experimental and theoretical studies, the purpose of which was to substantiate the technology of drilling wells isolation using new thermoplastic composite material. The basis of the proposed material is gravel, and secondary polyethylene terephthalate acts as a binding material. The use of the proposed insulation material avoids a number of disadvantages specific for traditional grouting mortars. The technology of material application provides its melting in a well by thermomechanical drilling. The article deals with the issues, related to the substantiation of the optimal formulation of a thermoplastic composite material based on secondary polyethylene terephthalate, and the determination of rational operating parameters of thermomechanical drilling, which allow to melt effectively the material at the bottom of a well. The possibility of material application for the insulation of absorbing horizons in borehole conditions has been proved. Based on the analysis of the heat balance at the bottom of a well, the calculation procedure has been proposed and the dependences of the velocity and time of thermomechanical melting of the grouting thermoplastic composite material on the operating parameters of drilling, thermal properties and geometric characteristics of the drill bit, have been determined

Design of wearable EEG device for seizures early detection

This paper presents the design of a wearable electroencephalography device and signal processing algorithm for early detection and forecasting of the epileptiform activity. The availability of the examination of functional brain activity for a prolonged period, outside of the hospital facilities, can provide new advantages in early diagnosis and intervention systems. In this study, the low-cost five-channel device is presented. The system consists of two main parts: the data acquisition and transmission units and processing algorithms. In order to create the robust epileptiform pattern recognition approach the application of statistical sampling and signal processing techniques are performed. The discrete wavelet and Hilbert-Huang transforms with principal component analysis are used in order to extract and select a low-dimension feature vector

Spiral wave chimeras for coupled oscillators with inertia

We report the appearance and the metamorphoses of spiral wave chimera states in coupled phase oscillators with inertia. First, when the coupling strength is small enough, the system behavior resembles classical two-dimensional (2D) Kuramoto-Shima spiral chimeras with bell-shape frequency characteristic of the incoherent cores. As the coupling increases, the cores acquire concentric regions of constant time-averaged frequencies, the chimera becomes quasiperiodic. Eventually, with a subsequent increase in the coupling strength, only one such region is left, i.e., the whole core becomes frequency-coherent. An essential modification of the system behavior occurs, when the parameter point enters the so-called solitary} region. Then, isolated oscillators are normally present on the spiral core background of the chimera states. These solitary oscillators do not participate in the common spiraling around the cores; instead, they start to oscillate with different time-averaged frequencies (Poincar\'e winding numbers). The number and the disposition of solitary oscillators can be any, given by the initial conditions. At a further increase in the coupling, the spiraling disappears, and the system behavior passes to a sort of spatiotemporal chaos.Comment: 13 pages, 9 figure

Stationary patterns of coherence and incoherence in two-dimensional arrays of non-locally coupled phase oscillators

Recently it has been shown that large arrays of identical oscillators with non-local coupling can have a remarkable type of solutions that display a stationary macroscopic pattern of coexisting regions with coherent and incoherent motion, often caled chimera states. We present here a detailed numerical study of the appearance of such solutions in two-dimensional arrays of coupled phase oscillators. We discover a variety of stationary patterns, including circular spots, stripe patterns, and patterns of multiple spirals. Here, the stationarity means that for increasing system size the locally averaged phase distributions tend to the stationary profile given by the corresponding thermodynamic limit equation

Cascades of Multi-headed Chimera States for Coupled Phase Oscillators

Chimera state is a recently discovered dynamical phenomenon in arrays of nonlocally coupled oscillators, that displays a self-organized spatial pattern of co-existing coherence and incoherence. We discuss the appearance of the chimera states in networks of phase oscillators with attractive and with repulsive interactions, i.e. when the coupling respectively favors synchronization or works against it. By systematically analyzing the dependence of the spatiotemporal dynamics on the level of coupling attractivity/repulsivity and the range of coupling, we uncover that different types of chimera states exist in wide domains of the parameter space as cascades of the states with increasing number of intervals of irregularity, so-called chimera's heads. We report three scenarios for the chimera birth: 1) via saddle-node bifurcation on a resonant invariant circle, also known as SNIC or SNIPER, 2) via blue-sky catastrophe, when two periodic orbits, stable and saddle, approach each other creating a saddle-node periodic orbit, and 3) via homoclinic transition with complex multistable dynamics including an "eight-like" limit cycle resulting eventually in a chimera state.Comment: 13 pages, 14 figure

Spiral wave chimeras for coupled oscillators with inertia

We report the appearance and the metamorphoses of spiral wave chimera states in coupled phase oscillators with inertia. First, when the coupling strength is small enough, the system behavior resembles classical two-dimensional (2D) Kuramoto-Shima spiral chimeras with bell-shape frequency characteristic of the incoherent cores [Y. Kuramoto, S.I. Shima, Prog. Theor. Phys. Supp. 150, 115 (2003); S.I. Shima, Y. Kuramoto, Phys. Rev. E. 69, 036213 (2004)]. As the coupling increases, the cores acquire concentric regions of constant time-averaged frequencies, the chimera becomes quasiperiodic. Eventually, with a subsequent increase in the coupling strength, only one such region is left, i.e., the whole core becomes frequency-coherent. An essential modification of the system behavior occurs, when the parameter point enters the so-called solitary region. Then, isolated oscillators are normally present on the spiral core background of the chimera states. These solitary oscillators do not participate in the common spiraling around the cores; instead, they start to oscillate with different time-averaged frequencies (Poincaré winding numbers). The number and the disposition of solitary oscillators can be any, given by the initial conditions. At a further increase in the coupling, the spiraling disappears, and the system behavior passes to a sort of spatiotemporal chaos

Optimized estimation of scattered radiation for X-ray image improvement: Realistic simulation

Image processing algorithms for compensation of the scattered radiation influence in X-ray imaging are proposed, studied and optimized by numerical simulation. These algorithms include the scattering estimation by convolution (superposition) technique, estimation of kernel functions by Monte Carlo (MC) simulation, the determination of the optimal number and shape of kernel functions and image segmentation. The determination of the number and shape of kernel functions was performed by the MC simulation of the realistic Zubal phantom and the clustering analysis of shape features of kernel functions. Testing simulation study of the algorithms for chest images at 75 keV proves that the optimal number of kernel functions is equal to 8. This number provides the three-fold contrast enhancement without using the anti-scatter grids. The achieved contrast is about 95% of the primary image contrast that exceeds contrast enhancements achieved with anti-scatter grids. An increased number of used kernel functions provides a better image contrast and better resolution of scattered radiation image, but estimation errors also increase due to the segmentation and deconvolution errors

The study of melting process of the new plugging material at thermomechanical isolation technology of permeable horizons of mine opening

The article presents the results of experimental and theoretical studies, the purpose of which was to substantiate the technology of drilling wells isolation using new thermoplastic composite material. The basis of the proposed material is gravel, and secondary polyethylene terephthalate acts as a binding material. The use of the proposed insulation material avoids a number of disadvantages specific for traditional grouting mortars. The technology of material application provides its melting in a well by thermomechanical drilling. The article deals with the issues, related to the substantiation of the optimal formulation of a thermoplastic composite material based on secondary polyethylene terephthalate, and the determination of rational operating parameters of thermomechanical drilling, which allow to melt effectively the material at the bottom of a well. The possibility of material application for the insulation of absorbing horizons in borehole conditions has been proved. Based on the analysis of the heat balance at the bottom of a well, the calculation procedure has been proposed and the dependences of the velocity and time of thermomechanical melting of the grouting thermoplastic composite material on the operating parameters of drilling, thermal properties and geometric characteristics of the drill bit, have been determined

Multiple scroll wave chimera states

We report the appearance of three-dimensional (3D) multiheaded chimera states that display cascades of self-organized spatiotemporal patterns of coexisting coherence and incoherence. We demonstrate that the number of incoherent chimera domains can grow additively under appropriate variations of the system parameters generating thereby head-adding cascades of the scroll wave chimeras. The phenomenon is derived for the Kuramoto model of N3 identical phase oscillators placed in the unit 3D cube with periodic boundary conditions, parameters being the coupling radius r and phase lag α. To obtain the multiheaded chimeras, we perform the so-called ‘cloning procedure’ as follows: choose a sample single-headed 3D chimera state, make appropriate scale transformation, and put some number of copies of them into the unit cube. After that, start numerical simulations with slightly perturbed initial conditions and continue them for a sufficiently long time to confirm or reject the state existence and stability. In this way it is found, that multiple scroll wave chimeras including those with incoherent rolls, Hopf links and trefoil knots admit this sort of multiheaded regeneration. On the other hand, multiple 3D chimeras without spiral rotations, like coherent and incoherent balls, tubes, crosses, and layers appear to be unstable and are destroyed rather fast even for arbitrarily small initial perturbations