Construction of mathematical modelling of a population of microalgae

This article devoted to the development of the mathematic model of the technological process of the chlorella cultivation process, its features and solving of this mathematic model. The Exponential growth of microalgae population under conditions of unlimited nutrient resources and population space proceeds at a rate proportional to the number of species of predominant cells and is described by the differential equation. In the presence of several inhibitors, specific velocity equations with the number of inhibitors can be used, but, as a rule, there are practically no elements acting as inhibitors in the cultivation of Chlorella microalgae. The modeling of this particular class of objects did not take into account the effect of inhibitors on the growth of microalgae. The consumption of nutrients to support the life of microalgae is described by the differential equation. In the course of this work, the processes of cultivation of microalgae were brought together into a system of equations. As a result, a system of differential equations of the technological process of Chlorella cultivation was obtained. Thus, the obtained system of equations describes the process of cultivation of microalgae and its technological process, implemented in a periodic mode.

Efficiency of electron beam extraction to the atmosphere in an accelerator based on ion-electron emission

The use of a modern element base makes it possible to create power supplies with a transition from a direct mode of generation of an auxiliary discharge to a pulse-periodic mode with a pulse repetition rate at the level of several tens of kHz. This allows for a more flexible adjustment of the discharge parameters, keeping the average value of its current, but changing its amplitude with a corresponding change in the pulse duty cycle. In this work, using an electron accelerator based on ion-electron emission, generating a wide-aperture electron beam, we research the effect of auxiliary discharge generation mode (direct and pulse-periodic) on the efficiency of electron beam extraction into the ambient atmosphere. It is shown that, in a direct mode of electron beam generation at an accelerating voltage of 150 kV, the beam extraction coefficient does not exceed 0.25. The possibility of increasing the extraction coefficient to K = 0.55 at the same accelerating voltage of 150 kV was demonstrated without making changes to the design of the accelerator, but switching to a pulsed-periodic mode of emission plasma generation.

Dynamics of Quality of Life Indicators in Patients with Chronic Synovitis of the Knee Joint after Arthroscopic Laser Double-mode Synovectomy

Background: The treatment of patients with chronic synovitis of the knee joint is a challenge faced by many doctors all around the world. Treatment of this pathology is often a difficult task. Aim. The aim of the study was improving the results of treatment of patients with chronic synovitis of the knee joint by applying two wavelengths of radiation. Material and methods. The treatment results of 50 patients with chronic synovitis of the knee joint aged 23 to 67 years with stage II-IV osteoarthritis according to the Kellgren-Lawrence classification were analyzed. All patients underwent arthroscopic sanation, partial laser synovectomy using LSP-IRE-Polus apparatus, wavelength 0,97 microns in pulse-periodic mode (pulse 100 ms, pause 50 ms) with power 5 W and wavelength 1,56 microns in continuous mode with power 5 W. Morphological examination of the synovial membrane and capsule was performed. Preoperative, 3, 6 and 12 month postoperative questionnaires were administered using the following scales and questionnaires: VAS, Leken index, WOMAC and KOOS. Results. Mean age (M) was 45.32±131, BMI 28.63±4.72kg/m2, duration of synovitis 2.26±1.91 years. A statistically significant improvement on the VAS, WOMAC, Leken, KOOS scales was noted by the 3rd month of postoperative follow-up. By the 6th month postoperatively, the results had further improved. The achieved results were preserved up to 12 months after surgery (P <0.05). Conclusion. The results suggest that the proposed technique may be introduced into clinical practice.

On the Existence of a Periodic Mode in a Nonlinear System

We consider a nonlinear control system with a bang-bang hysteresis control, which is a simplified model of a thermal energy harvester. We obtain conditions on the controller and the system parameters guaranteeing the existence of a periodic mode in the system.

Optimization of VFD Operations for Transporting Equipment of Packages

This study is focused on the efficiency of automated transferring system of packages equipped by variable-frequency drive (VFD) and servo drive motor. It was found that rotation frequency of induction motors and linear speed of servo drive decisively affected the unit efficiency that operates in the periodic mode. The system duty cycle was divided in two separate parts taking into account time spans needed to complete the specific tasks by each separate equipment of the system. In order to reduce the power usage of the system, the duration of each part of cycle was extended. Lowered electricity consumption leads to the extension of each cycle’s stage operating times. Frequencies of motors and linear speed of servo drive motors were optimized depending on cycle stages duration. Optimized frequency and linear speed values were calculated and loaded into motors controllers, and the efficiency of each separate equipment was measured, as well as total efficiency of the system. Experimental system debugging using optimized parameters proved that system efficiency increases up to 60 %, and that is closely matched with calculated values.

Production of Graphene-Containing Suspensions for Liquid-Phase Shear Exfoliation of Graphite

A method and device for obtaining graphene-containing suspensions by liquid-phase shear exfoliation of graphite in a continuous mode have been developed. The comparison of the intensities of the process of exfoliation of graphite in the periodic and continuous modes was carried out and it was found that the intensity of the exfoliation process in the continuous mode is higher than in the periodic one. The limiting concentration of graphene structures in a suspension is reached 1.5 times faster when using an apparatus operating in a continuous mode than in a periodic mode, and its numerical value is greater (by at least 25 %).

Трансформация отрывного турбулентного течения в конической лунке на стенке узкого канала и снижение гидравлических потерь c увеличением конусности

Based on the solution of the URANS closed with a modified model of turbulence MSST, the separated flow in a narrow channel with a conical dimple on the wall with a coning angle of θ was calculated. It is noted that there is a sharp transition from the periodic mode with two alternately changing vortices in close to cylindrical (θ = 10о-22.5о) dimples to modes with periodic low-frequency oscillations of inclined mono-tornado structures at moderate θ (30о-37.5о) and with steady vortex structures at θ above 45о. Relative hydraulic losses in the irradiated section of the channel with an increase in θ remain at the level of 1.23-1.24 to θ = 45о, and then quickly decrease by almost 1.5 times to 1.16 at θ = 60о.