No abstract

Echo-dynamography (EDG) is a method for visualizing left ventricular (LV) blood flow based on cardiac Doppler measurement in which blood flow component perpendicular to the ultrasonic beam is deduced by applying fluid dynamics theories to two-dimensional (2D) distribution of blood flow component along the ultrasonic beam. EDG has been validated by numerical simulation and particle image velocimetry of model circulation. However, these validations were too simple to reproduce unstable and asymmetrical flow in a beating heart. In the present study, EDG is compared with three-directional (3D) blood flow distribution on the same plane obtained with phase contrast magnetic resonance angiography (PCMRA) for clinical validation. Moreover, the location and vorticity of the vortex flow in LV are measured quantitatively and the relation to echocardiographic parameters of systolic and diastolic functions is discussed. 3D components of blood flow on a plane were obtained with triple scans of the same plane with ECG trigger and breath holding; 1) phase encode (x-axis), 2) read out (y-axis) and 3) slice selection (z-axis). After the acquisition of MRA dataset, color Doppler dataset of the same plane was acquired and 2D velocity distribution was obtained with EDG in MATLAB programs. EDG and PCMRA showed similar velocity vector distribution and formation of LV vortex flow. The vortex at mid diastolic phase was strongly affected by early diastolic filling while the vortex at isometric contraction was affected by atrial filling. EDG gained a new insight on systolic-diastolic coupling from the view point of LV blood flow such as LV vortex formation.

The article presents a mathematical model of coal self-heating in the stack in which the heat exchange and gas exchange processes are described by a system of two non-linear differential equations of the second order with respect to the temperature t of coal self-heating and the volume fraction C of oxygen in the voids of the stack with boundary and initial conditions. The differential equations took into account that self-heating of coal in the stack and appearance of spontaneous combustion are observed in a relatively small layer adjacent to the surface of its contact with the air and called the zone of oxygen influence. In the mathematical model, the influence on the process of coal self-heating of parameter F- specific heat release power was taken into account, which in addition characterises the stability of coal during storage. When compiling the differential equations, such physical parameters as thermal conductivity, diffusion coefficient, specific heat capacity of coal in the stack, bulk density, thermal effect of oxidation, stack voidness, temperature coefficient of exponential growth of heat release power were also used. For numerical implementation of the mathematical model, dimensionless variables and criteria were introduced, which allowed us to apply the net method. Analysis of the obtained results allowed to get: change in the stack temperature profiles with time; change in the stack oxygen concentration profiles with time; influence on the stack temperature profile of the specific heat release power; influence on the stack temperature profile of the parameter characterizing exponential growth of heat release intensity with temperature increase. It has been determined that the dynamics of coal self-heating in the stack is mostly influenced by the Lykov criterion, proportional to the diffusion coefficient, and the Nusselt criterion related to the effective thermal conductivity and to the effective thermal diffusivity of coal. The obtained results suggest that self-heating in the stack is due on the one hand to intensive penetration of air oxygen and on the other hand to a weakened heat transfer. Self-heating and the transition of self-heating into ignition are associated with the occurrence of turbulent diffusion in the stack, arising from increased thermal blowing, whose impact can be enhanced by directing it perpendicular to the surface of the stack.

To prevent emergency situations during the flood period, a set of measures to monitor the dam status of the Sherubay-Nurinsk reservoir was carried out. The investigation included a total station survey of the cross-section contour at 100 meters along the characteristic points of the dam. The method of georadar scanning was also used. According to the data obtained, the dam stability was calculated in the software Slider 7.0. The selection of sites for static and filtration stability calcula-tions was carried out on the basis of the available geodetic survey of the actual state of the reservoir dam. Analysis of the results of the calculation of the stability of the dam slopes showed that the structure is in a stable state, as the resulting safety factors vary from 1.874 to 2.729, which is much higher than the standard level, which is equal to the value of 1.26 for the II class of construction.

Целью исследования является изучение инженерногеологических условий грунтов основания и тела дамбы хвостохранилища с дальнейшим расчетом параметров устойчивости дамбы для выбора мероприятий, направленных на оценку возможности эксплуатации хвостохранилища с последующей его консервацией (ликвидацией) при достижении расчетных значений. Разработаны рекомендации и мероприятия по выводу из эксплуатации и переводу хвостохранилища на консервацию с последующей его ликвидацией при обеспечении промышленной и экологической безопасности для окружающей среды. С учетом физико-механических свойств грунтов и пород основания, погодно-климатических условий, результатов моделирования обоснована методика расчета для проведения инженерно-строительных работ, направленных на обеспечение устойчивости внешних откосов дамбы.