Discrete Vortex Cylinders Method for Calculating the Helicopter Rotor-Induced Velocity

A new vortex model of a helicopter rotor with an infinite number of blades is proposed, based on Shaidakov’s linear disk theory for calculating inductive speeds at any point in space in the helicopter area. It is proposed to consider the helicopter rotor and the behind vortex column as a system of discrete vortex cylinders. This allows building a matrix of the influence of the vortex system under consideration on any set of points, for example, the calculated points on the rotor itself, on the tail rotor, etc. The model allows calculating inductive velocities at any point near the helicopter using matrix multiplication operation. It is shown that the classical results for the momentum theory remain constant even in the discrete simulation of the helicopter rotor vortex system. The structure of the air flow behind the rotor and the simulation results obtained by the proposed method is compared with the structure of the tip vortices and the results of the blade vortex theory. In addition, the experimental data were compared with the simulation results to verify the correctness of the model under real operating conditions by the helicopter trimming

TG study of the Li[0.4]Fe[2.4]Zn[0.2]O[4] ferrite synthesis

In this paper, the kinetic analysis of Li-Zn ferrite synthesis was studied using thermogravimetry (TG) method through the simultaneous application of non-linear regression to several measurements run at different heating rates (multivariate non-linear regression). Using TG-curves obtained for the four heating rates and Netzsch Thermokinetics software package, the kinetic models with minimal adjustable parameters were selected to quantitatively describe the reaction of Li-Zn ferrite synthesis. It was shown that the experimental TG-curves clearly suggest a two-step process for the ferrite synthesis and therefore a model-fitting kinetic analysis based on multivariate non-linear regressions was conducted. The complex reaction was described by a two-step reaction scheme consisting of sequential reaction steps. It is established that the best results were obtained using the Yander three-dimensional diffusion model at the first stage and Ginstling-Bronstein model at the second step. The kinetic parameters for lithium-zinc ferrite synthesis reaction were found and discussed

Investigation of heating rate effect on solid-phase interaction in Li[2]CO[3]-Fe[2]O[3] reaction mixture

The influence of heating rate on solid-phase interaction in Li[2]CO[3]-Fe[2]O[3] reaction mixture was investigated by thermal analysis method. The powder mixture components were in the ratio corresponding to LiFe[5]O[8] ferrite. The ferrite synthesis was performed by thermal heating of mixture reagents in thermal analyzer up to 800 °С in air at various heating rates in the ranges (5-50) °С/min. The results showed that the heating rate affects the solid-phase interaction in Li[2]CO[3] - Fe[2]O[3] reaction mixture. The reaction phase formation is accompanied by heat endothermic effect, which was observed in the DSC curve in the form of a complex broad peak. For all samples, this complex peaks were decomposed into simpler peaks, and thereby, the enthalpies of the individual phase transitions were determined. It was shown that the heating rate affects the values of enthalpy and temperatures of heat endothermic effects, so that the high heating rate shifts the proceeding of reaction to higher temperatures

Investigation of oxidation process of mechanically activated ultrafine iron powders

The oxidation of mechanically activated ultrafine iron powders was studied using X-ray powder diffraction and thermogravimetric analyzes. The powders with average particles size of 100 nm were made by the electric explosion of wire, and were subjected to mechanical activation in planetary ball mill for 15 and 40 minutes. It was shown that a certain amount of FeO phase is formed during mechanical activation of ultrafine iron powders. According to thermogravimetric analysis, the oxidation process of non-milled ultrafine iron powders is a complex process and occurs in three stages. The preliminary mechanical activation of powders considerably changes the nature of the iron powders oxidation, leads to increasing in the temperature of oxidation onset and shifts the reaction to higher temperatures. For the milled powders, the oxidation is more simple process and occurs in a single step

The study of the ferroelectric properties of lithium-titanium ferrite

Loop-shaped dependences of the electric polarization on the electric field strength (the dielectric hysteresis) are registered for the first time for polycrystalline Li-Ti ferrite. Temperature evolution of the hysteresis loop parameters is investigated for ferrite samples. A thermal Barkhausen effect is detected during heating and cooling of ferrite specimens prepolarized in an electric field. The results obtained can be interpreted from the viewpoint of the Maxwell-Wagner relaxation polarization or induced ferroelectric-like state in the electric ferrite subsystem

Impact of ozone treatment on dissolved organic matter in land-based recirculating aquaculture systems studied by Fourier transform ion cyclotron resonance mass spectrometry

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Processing line for industrial radiation-thermal synthesis of doped lithium ferrite powders

The paper considers the issues of industrial production of doped lithium ferrite powders by radiation-thermal method. A technological scheme of the processing line is suggested. The radiation-thermal technological scheme enables production of powders with technical characteristics close to the required ones under relatively low temperature annealing conditions without intermediate mixing. The optimal conditions of the radiation-thermal synthesis are achieved isothermally under irradiation by the electron beam with energy of 2.5 MeV in the temperature range of 700-750 °С within~ 120 min

TG, DSC, XRD, and SEM studies of the substituted lithium ferrite formation from milled Sm2O3/Fe2O3/Li2CO3 precursors

Formation of substituted lithium ferrite Li0.5SmxFe2.5–xO4 (where x = 0.06 and 0.2) from Sm2O3/Fe2O3/Li2CO2 precursors was studied by X-ray diffraction analysis, thermogravimetry, differential scanning calorimetry, and scanning electron microscopy. The mixture of powders was subjected to preliminary mechanical activation in a planetary mill. We analyzed samples based on the precursors and synthesized at 900 °C for 4 h in a laboratory furnace. It was found that ball milling of the precursors mixture in a planetary mill increases the powder reactivity. In spite of this, no substituted lithium ferrites were formed. It was shown that a two-phase composite that consists of pure lithium ferrite Li0.5Fe2.5O4 and SmFeO3 is formed during synthesis. An increase in the Sm2O3 content in the initial mixture provides an increase in the amount of the formed SmFeO3 phase. The synthesis of Li0.5Fe2.5O4 ferrite was confirmed by XRD analysis data, the Curie temperature (627–630 °C) measured using TG analysis in a magnetic field, and by the presence of an endothermic peak on the DSC curve corresponding to the order–disorder transition in the Li0.5Fe2.5O4 phase

In vivo non-invasive staining-free visualization of dermal mast cells in healthy, allergy and mastocytosis humans using two-photon fluorescence lifetime imaging

Mast cells (MCs) are multifunctional cells of the immune system and are found in skin and all major tissues of the body. They contribute to the pathology of several diseases including urticaria, psoriasis, atopic dermatitis and mastocytosis where they are increased at lesional sites. Histomorphometric analysis of skin biopsies serves as a routine method for the assessment of MC numbers and their activation status, which comes with major limitations. As of now, non-invasive techniques to study MCs in vivo are not available. Here, we describe a label-free imaging technique to visualize MCs and their activation status in the human papillary dermis in vivo. This technique uses two-photon excited fluorescence lifetime imaging (TPE-FLIM) signatures, which are different for MCs and other dermal components. TPE-FLIM allows for the visualization and quantification of dermal MCs in healthy subjects and patients with skin diseases. Moreover, TPE-FLIM can differentiate between two MC populations in the papillary dermis in vivo—resting and activated MCs with a sensitivity of 0.81 and 0.87 and a specificity of 0.85 and 0.84, respectively. Results obtained on healthy volunteers and allergy and mastocytosis patients indicate the existence of other MC subpopulations within known resting and activated MC populations. The developed method may become an important tool for non-invasive in vivo diagnostics and therapy control in dermatology and immunology, which will help to better understand pathomechanisms involving MC accumulation, activation and degranulation and to characterize the effects of therapies that target MCs