Gas-air Mixture Research Articles

Experimental Evaluation of CNG Substitution Ratio on Exhaust Gas Emissions of Diesel/CNG Dual Fuel Combustion

The addition of Compressed natural gas as a complement to diesel in compression ignition engines in dual-fuel combustion mode is a viable technology for increasing efficiency and lowering emissions. This work investigates the impact of a dual-fuel operating mode on the engine exhaust pollutant emissions of a diesel engine using compressed natural gas as the principal fuel and neat diesel as the pilot fuel. Compressed natural gas was injected into an intake manifold of a single-cylinder diesel test engine under different engine operating parameters, and up to 80% substitution was attained. And diesel fuel was injected after the compressed natural gas air mixture was compressed. The tests were carried out at five different compression ratios ranging from 13:1 to 15:1 in steps of 0.5:1. The experiment study revealed that injecting CNG into diesel engines via dual fuel combustion significantly impacted exhaust gas emissions compared to pure diesel combustion. The Carbon monoxide (CO) and hydrocarbon (HC) emissions were increased, while carbon dioxide (CO2), nitrogen oxide (NOX) and smoke opacity were decreased in dual fuel combustion compared to single diesel fuel.

The first experience in the treatment of large penetrating wounds of the sclera using expanded primary microsurgical treatment

BACKGROUND: According to the literature, the absence of pattern vision in the outcome of open wounds of the eyeball is observed in 2530% of cases, and in the presence of large wounds with multiple injuries of intraocular structures, it is 6180%.
 AIM: to present the results of expanded microsurgical treatment of large penetrating corneoscleral and scleral wounds involving the zone III, to evaluate the results of the given algorithm for severe penetrating injury care.
 MATERIALS AND METHODS: Presented are the results of treatment of 24 patients with large penetrating corneoscleral and scleral wounds, massive hemophthalmos, and other injuries. All patients underwent primary microsurgical treatment according to a modified, expanded algorithm, which, in addition to suturing the fibrous capsule of the eye, included subtotal vitrectomy, primary treatment of retinal and choroidal wounds, the use of autologous conditioned plasma (P-PRP) , tamponade with silicone oil or a gas-air mixture.
 RESULTS: Evaluation of treatment results was carried out on day 3, after 1 and 6 months. Special attention was paid to the identification of signs of proliferative vitreoretinopathy as most important in terms of prognosis. After 6 months, visual acuity above 0.1 was noted in 10 patients, 0.020.09 in 12, absence of pattern vision in 2. Signs of development and progression of PVR during 6 months were noted in 7 patients (29.2%), of which repeated surgeries were performed in 5 cases.
 CONCLUSIONS: The new advanced algorithm of primary microsurgical treatment allows to improve functional results in severe cases of penetrating eye injury.

Experimental and reaction kinetics studies on deflagration characteristics of liquefied petroleum gas-air mixture with different compositions in confined space

To assess the hazardous impact of liquefied petroleum gas (LPG), this study investigated its macro–micro deflagration characteristics under various compositions and equivalence ratios using a 20 L spherical experimental apparatus and CHEMKIN-Pro kinetic software. The findings are as follows: when the equivalence ratio was 1.2, the LPG exhibited peak values for the maximum explosion pressure (pmax), maximum explosion pressure rise rate ((dp/dt)max), deflagration index (KG), and average flame propagation velocity (v). Furthermore, the (dp/dt)max, KG, and v increased with increasing the proportion of C3H8. In the LPG chain reaction, the most influential steps in terms of promotion and inhibition were R1: H + O2 = O + OH and R104: 2CH3(+M) = C2H6(+M), respectively. C2H4 gradually accumulated during the chain initiation phase and rapidly depleted as the temperature sharply increased. Hence, to effectively inhibit LPG explosion, it is recommended to develop inhibitors capable of eliminating reactive radicals (such as H*, O*, and OH*) and targeted inhibitors that specifically inhibit the reaction involving C2H4. Additionally, augmenting the C3H8 proportion in LPG can mitigate the emission of toxic and harmful gases, such as CO and CO2. This study has significant theoretical and practical implications for the safe, environmentally friendly, and efficient use of LPG.

Structure of the Device and Experimental Research of Verifying the Functionality of Elements of Easy-Dropped Construction

This article analyzes the current state of explosion protection in the world. As a result of the analysis, it was determined that the main modern method of explosion protection is the use of easy-dropped construction (hereinafter - EDC). There are various methods for calculating the required area of the EDC, but to confirm the reliability of the calculations, the selection of the material that performs the function of the EDC, geometrical parameters and excess pressure of operation, it is necessary to conduct experimental research. The existing experimental devices for testing EDC for excess explosion pressure are given. The designs and drawbacks of these devices are considered. The design features of the constructed unit for checking the functionality of elements of easy-dropped construction (hereinafter referred to as the unit) and the main advantages compared to other experimental units are described. A scheme of the device and its structure is given. The required amount of propane-butane was calculated to obtain an excess explosion pressure of 5 kPa. Based on the results of the tests, a graph of the change in the excess pressure of the explosion over time is plotted and the value of the excess pressure of the explosion in a closed volume depending on the concentration of the gas mixture of propane-butane with air, which is formed in the closed volume, and the change in the excess pressure of the explosion after the activation of the EDC were investigated. A graph of the influence of the concentration of the gas-air mixture on the excess pressure acting on the EDC is plotted. The design parameters of the device and its location, the limit values of the excess pressure of the explosion, the minimum amount of gas to create the required excess pressure of the explosion are substantiated. The considered device provides an experimental determination of the values of the overpressure of the operation of EDC of typical sizes and allows conducting experimental research of the operation of the EDC under the influence of various values of the overpressure of the explosion with the required accuracy.

A new approach to producing a prospective energy resource based on coalmine methane

The paper describes topical issues of a prospective method for coalmine methane utilization for obtaining an additional valuable energy resource for the regional development of coal-mining areas. It is noted that the development of the extraction of methane resources is very urgent and is of great economic importance for ensuring the energy independence of Ukraine. The experience and technologies of using methane and coalmine gas by global coal-mining companies are analyzed. Modern prospects and opportunities for using coal gas are studied. There is a need to transform the coalmine methane removal system and directions for maximizing the use of its resources in a wide range of concentrations in the composition of gas-air mixtures based on the development of innovative technologies to improve the efficiency and cost-effectiveness of functioning coal-mining enterprises. Attention is focused on the advantages of using gas hydrate technologies for obtaining additional energy resource under conditions of changing coalmine methane concentrations. The specifics of the process of mixed gas hydrate formation from gas mixtures of various geneses have been studied. It has been revealed that it is the coalmine gas-methane composition that determines and forms the basic condition for hydrate formation. The thermobaric conditions for the hydrate formation process at different methane concentrations in gas mixtures of degassing systems have been experimentally determined. The results obtained are the basis for further research on efficiency of creating gas hydrates from coalmine methane and determining its minimum permissible concentration in the gas mixture of degassing systems according to the technological and economic criteria of hydrate formation.

RESULTS OF INDUSTRIAL TESTS OF A CONDENSING VAPOR RECOVERY UNIT AT AN OFFSHORE OIL TERMINAL

An effective method of reducing vapor emissions of liquid hydrocarbons, creating safe operating conditions for facilities for loading oil products into vehicles is the use of vapor recovery units (VRU). Among the available types of VRU, condensing installations are distinguished, the operation of which is based on the difference in the condensation temperatures of air and petroleum product vapors. To the advantages of condensing VRU developers refer: 1) safety; 2) low hydraulic resistance; 3) production of condensate of high commercial quality; 4) the possibility of accounting for the captured product; 5) the absence of secondary contaminated waste; 6) the practical absence of the need to purchase and dispose of consumables.
 The article presents the results of tests of the condensing VRU, called the «Condensation and Dispersion Complex», during the gasoline shipment at one of the offshore oil terminals in the spring and summer period.
 During the condensating VRU tests, the average degree of purification efficiency of the gas-air mixture (GAM) from gasoline vapors is established, which is significantly lower than the suppliers of condensing VRU declare and is
 completely insufficient to solve environmental problems. The content of hydrocarbons in the GAM at the output of the VRU turned out to be several times higher than was stated by the developer.
 The reason for this negative result is insufficient deep cooling of the gas-air mixture. It has been initially chosen incorrectly, because it does not take into account the accumulated experience in the world of using condensating URPs. The lowest achieved GAM temperature is several degrees higher than the coolant temperature in the condenser heat exchangers, which indicates an incorrect choice of condensation criteria.
 The amount of gasoline that was captured during the loading of one tanker was determined, as well as the amount of hydrate inhibitor required for this and the electricity consumption. It is established that the consumption of consumables during the operation of the condensing URP, called the «Condensation and Dispersion Complex», is rather high. Therefore, the developers' statement about the absence of consumption by the installation of consumables is a marketing technique.

Influence of initiation conditions of methane-air mixture on the explosion parameters in the degasation pipeline

Purpose. Increasing the safety of personnel at underground works in case of the threat of gas explosions, including explosion of degassing pipelines by taking into account the influence of the place of initiation of the explosion and the mode of combustion when calculating the parameters of the explosion. Mathematical modeling of the process of ignition and combustion of the methane-air mixture in the degassing pipeline. Research methods. nalysis and generalization of theoretical studies, numerical simulation of gas-dynamic detonation combustion of a gas-air mixture, including a model of chemical combustion kinetics, which, on the whole, allows one to trace the dynamics of formation of shock air waves in conditions of mine workings. Mathematic processing of the results of the experiment by the method of least squares. When solving the nonlinear regression equations, linearization was used by the method of logarithm. Results. It is established that the combustion dynamics of the gas-air mixture has a decisive influence on the formation of UVB: in the deflagration combustion mode of the gas-air mixture, with the initiation at the edge of the cloud, the length of the blast wave is increased 3.6 times in the direction opposite to combustion, and the wave amplitude by 10% spread of flame. In the detonation mode, the effect of a directed explosion is observed, in which the amplitude of the shock air wave is opposite to the motion of the detonation wave 5 times less than in the direct shock air wave. The model of an instantaneous volumetric explosion, in comparison with combustion models, yields an underestimated amplitude value. Scientific novelty. As a result of numerical modeling of the ignition and combustion of the sealed section of the mine atmosphere, regularities in the formation and propagation of shock air waves, the dependence of their parameters on the combustion regime and the location of the initiation of the gas-air mixture were obtained. Practical value. The conducted research allows to improve the method of calculating the resistance of degassing pipelines and their elements to explosive load.

Toxicological and hygienic assessment of modern thermo-insulating polymer materials during thermal exposure

Introduction. Polyethylene and synthetic foam caoutchouc are used for thermal insulation of communications, at temperatures not exceeding 90 °C and 105 °C, respectively. Data on how these materials will behave in the appropriate temperature conditions was not be found. 
 The purpose of the study was to conduct a toxicological and hygienic assessment of products made of polyethylene foam and synthetic foam rubber under thermal exposure.
 Materials and methods. The thermal effect on the studied samples was modelled in a climate chamber. The time interval during the mass loss of the samples was determined, a sanitary and chemical study of the gas-air mixture in the climatic chamber was carried out. To conduct a toxicological and hygienic study in animals, a swim-escape conditioned active avoidance response was developed.
 Results. Under thermal (90 °C) exposure for 72 hours to polyethylene tube, a loss of 0.77% of the initial mass of the sample occurs. Thermal exposure (105 °C) to synthetic foam caoutchouc resulted in a loss of 15.3% of the initial mass of the sample for 108 hours, while pronounced changes in the appearance of the samples were determined. When conducting a sanitary and chemical study in the climate chamber, an increase in the concentration of carbon monoxide was determined after 12, 24, and 72 hours and hydrogen chloride after 12 and 24 hours following the onset of thermal exposure compared with the values of their average daily maximum permissible concentration. Thermal exposure to the sample and synthetic foam caoutchouc led to an increase in the concentration of ammonia, carbon monoxide and hydrogen chloride 12 and 24 hours after the start of exposure compared with the average daily maximum permissible concentration. During the toxicological and hygienic study, animals exposed to thermal degradation products of the materials under study were revealed to show learning disabilities.
 Limitations. They are conditioned by the methodology of the study. A quantitative analysis of some gaseous thermal degradation products released into the climate chamber was performed, without taking into account the aerosols formed.
 Conclusion. Thermal insulation materials made of synthetic foam rubber and polyethylene foam lose their structural properties when they are operated in the maximum permissible temperature conditions (105 °C and 90 °C, respectively). When they are used in appropriate temperature conditions, the formation of toxic products occurs, the inhalation effect of which leads to a disturbances of the learning ability in laboratory animals.

Nanocatalyst for carbon monoxide oxidation based on palladium(II), copper(II) salts, and carbon fiber material

The phase composition, textural, and activity of catalysts for the carbon monoxide low-temperature oxidation based on two series of non-woven carbon fiber material samples CFM-I and CFM-II, and K2PdCl4, Cu(NO3)2, KBr basic components were studied in this work. Catalysts and CFMs were studied by XRD, nitrogen and water vapor adsorption/desorption, and atomic absorption spectrophotometry methods. It has been found that the basic components K2PdCl4 and Cu(NO3)2 deposited on a microporous carbon surface undergo changes and form an X-ray amorphous Pd0 phase and a paratacamite—Cu2(OH)3Cl nanocrystalline phase. The catalysts were tested at carbon monoxide initial concentrations of 300 mg/m3 with an effective contact time of the catalyst with the gas–air mixture from 0.12 to 0.50 s. Catalysts provide air purification from CO to concentrations below MPCCO (20 mg/m3) and can be used in respiratory devices. The maximum catalytic activity is observed when the content of palladium in the catalyst is 1.70⋅10−4 mol/g and the content of copper (ІІ) is 4.68⋅10−4 mol/g.

Effects of Various Types of Vacuum Cold Plasma Treatment on the Chemical and Functional Properties of Whey Protein Isolate with a Focus on Interfacial Properties

Vacuum cold plasma (VCP), a novel non-thermal processing technology used to modify the physicochemical properties and functionalities of food materials, was applied to whey protein isolate (WPI). The treatment affects the protein chemistry and, as a result, leads to differences in the behavior in solution and at interfaces. To minimize the undesirable effects of high oxidation and to increase the effectiveness of reactive species, the VCP treatment was applied at low pressure using different types of gases (air, combination of argon and air, and sulfur hexafluoride (SF6)). The treatment led to a decrease in the sulfur content and an increase in the carbonyl content, evidenced by oxidation reactions and enhanced disulfide bond formation, as well as cross-linking of protein molecules. Fluorescence-based indicators suggest that the hydrophobicity of the proteins as well as their aggregation increase after VCP treatment with an argon–air gas mixture; however, it decreases after VCP treatments with air and SF6. The chemical modifications further lead to changes in the pH of aqueous WPI solutions, as well as the average size and ζ-potential of WPI aggregates. Moreover, the dynamic surface tension, surface dilational elasticity, and the thickness of the WPI adsorption layers at the air/water interface depend on the VCP type. SF6 plasma treatment leads to a significant decrease in pH and an increase in the ζ-potential, and consequently to a significant increase in the aggregate size. The dynamic surface tension as well as the adsorption rates increase after SF6VCP treatment, but decrease after air–VCP and argon–air–VCP treatments. The adsorbed WPI aggregates form strong viscoelastic interfacial layers, the thickness of which depends on the type of VCP treatment.

High-frequency measurement of concentration in an isothermal methane–air gas mixture using spontaneous Raman spectroscopy

A high-frequency (1.5 kHz) spontaneous Raman spectroscopy measurement technique is developed and applied to measure external fluctuations generated in the local concentration of an isothermal binary gas mixture of methane and air. Raman excitation is provided by a high-frequency laser at 527 nm in dual-pulsed mode. The Stokes Raman signal is collected using an EMCCD camera coupled to a high-frequency intensifier as a shutter. The emitted signal is collected over the 596–627 nm wavelength range, which allows for the simultaneous tracking of methane and nitrogen Stokes Q-branch mode signals. Calibration curves are initially obtained for each species ({text{CH}}_{4} and {mathrm{N}}_{2}) based on steady-state concentrations, and further corrected during use to detect local unsteady mixture fluctuations at gas pulsation frequencies up to 250 Hz. The main novelty is the demonstration of Raman spectroscopy for the simultaneous multispecies measurement of unsteady concentrations of gas-phase methane and air mixtures using a laser beam with a high-repetition rate, low energy per pulse, combined with a high-frequency intensifier and a single camera.

Экспериментальное определение устойчивости сборных металлических конструкций к взрывным нагрузкам

Introduction. Emergency gas explosions occur at industrial facilities as well as in residential buildings. An analysis of normative documents in the field of explosion resistance of buildings and structures subject to an accidental gas explosion has been carried out which revealed a lack of requirements for their explosion resistance and methods of testing their resistance to a deflagration accidental explosion. Objective. A team from the Institute of Comprehensive Construction Safety at the National Research Moscow State University of Civil Engineering (NRU MGSU) developed a test procedure for determining the resistance of prefabricated metal structures to a deflagration explosion of an air-gas mixture and conducted a study including two experiments and analysis of the results to determine the application of building envelopes in the field of explosion protection of buildings and structures against excessive pressure deflagration Materials and methods. The researches have been carried out with the use of a test bench for light-load-bearing constructions according to GOST R 56289. Fabricated metal structures, consisting of 200-mm-thick wall sandwich -panels and metal frame of two steel pipes of 100-mm section were used as test specimens. In the course of the investigations, the failure of the locking joint of the panels and the complete failure of the enclosing structure were monitored. Result s and discussion. Studies have shown that with an overpressure of 17–18 kPa and the exposure time of blast load of at least 250 ms, a significant deformation of the structure with a residual deflection was observed. Complete destruction of the structure occurred at the intensity of the dynamic impact in a 45–47 kPa blast wave and the exposure time of the blast load about 400 ms. Co nclusions. It has been established that the prefabricated metal structure consisting of wall sandwich panels and a metal frame can be used as an explosion-proof protective fence at production facilities in the calculation of blast loads. Several variants of increasing resistance of the structure to deflagration explosion have been proposed.

Simulation of Multi-Phase Flow to Test the Effectiveness of the Casting Yard Aspiration System

The metallurgical industry is in second place among all other industries in terms of emissions into the atmosphere, and air pollution is the main cause of environmental problems arising from the activities of metallurgical enterprises. In some existing systems for localization, in the trapping and removal of dust emissions from tapholes and cast-iron gutters of foundries, air flow parameters may differ from the optimal ones for solving aspiration problems. The largest emissions are observed in the area of the taphole (40–60%) and from the ladles during their filling (35–50%). In this paper, it is proposed to consider a variant of the blast furnace aspiration system with the simultaneous supply of a dust–gas–air mixture from two-side smoke exhausters and two upper hoods with two simultaneously operating tapholes, that is, when the blast furnace operates in the maximum emissions mode. This article proposes an assessment of the effectiveness of the modernized blast furnace aspiration system using computer CFD modeling, where its main parameters are given. It is shown that the efficiency of dust collection in the proposed system is more than 90%, and the speed of the gas–dust mixture is no lower than 20 m/s, which prevents gravitational settling on the walls. The distribution fields of temperatures and velocities are obtained for further engineering analysis and the possible improvement of aspiration systems.

Experimental identification of the electrical discharge on a surface gap spark plug

The main objective of the research is to assess the influence of the spark plug electrodes geometry on the structure of the electric arc. This issue is increasingly important in modern gas-fueled engines with lean and stratified air-gas mixtures. To explain the influence of electrode geometry on selected spark discharge indicators, optical tests were conducted, and the parameters of the test history, together with the movies of the discharging process, were recorded and analyzed. The tests were carried out comparatively for two types of spark plugs on the test stand: conventional spark plug and spark plug with a flat ground electrode. It has been found that using flat plug electrodes allows a larger spark area covered by the electric arc without losing the intensity of radiation. More, using an unconventional spark plug results in a shorter discharge time relative to the conventional spark plug, while the geometry of the conventional spark plug allows for maintaining a stable electric arc with a minimum tendency for creeping.

OPERATION FEATURES OF ENVIRONMENTALLY EFFICIENT BOILER PLANTS OF MUNICIPAL THERMAL POWER ENGINEERING

The work is devoted to research on the improvement of thermal energy production technologies in gas-consuming heating boiler installations while improving their environmental performance and increasing the operation reliability. The work purpose is to study the heat and humidity modes of the air-supply ducts of boiler plants with exhaust gases recirculation systems into the blown air. The main objectives of the study are: to determine the thermal parameters of a heating boiler with a 2 MW heating capacity with a exhaust gases recirculation system mixed with blown air into its furnace space under conditions of using heat recovery technologies and without them; determination and analysis the heat and humidity parameters of this mixture in different operating modes of boiler plants. Known thermal calculation methods of boiler plants and data from our own experimental studies of heat transfer during deep cooling of boiler plant exhaust gases were used. The thermal calculation results of the heating boiler with a system for exhaust gas recirculation into its furnace space mixed with blown air are presented. The regularities of changes in the adiabatic combustion temperature and heat-humidity characteristics of the above mixture depending on the boiler heat load in different its operation modes during the heating period and the share of flue gas recirculation from 10 to 20 % were established. The research results show that the introduction of recirculation gases leads to a decrease by 150 – 250 °С of the adiabatic combustion temperature tad due to the need to consume fuel heat for heating the introduced ballast and the greater of the recirculation share s the lower the level of the indicated temperature. The research results also showed that gas recirculation causes insignificant (in the range of 0.5 – 4.7 °С) changes in the temperature of the boiler exhaust gases. Based on the data obtained, the change regularities in the heat-humidity characteristics (temperature and dew point) of the mixture of recirculated gases and air in different boiler operating modes during the heating period and under the studied recirculation shares were established. It is shown that recirculation causes condensate formation on the surfaces of air ducts in all operating modes of boiler and in some modes their icing is possible. To prevent these negative phenomena, it is necessary to apply measures to increase the temperature of the gas-air mixture by a value not less than Δtsum = 15 – 35 °С.

Effects of Adding Ethanol to Natural Gas-Air Mixture on Combustion and Emissions of Natural Gas-Diesel Dual Fuel Engine Based on GT-Power

ABSTRACT To resolve power reduction and engine knock, we investigate the influence of adding ethanol to the natural gas (NG)-air mixture on the combustion and emissions of NG-diesel dual-fuel (NDDF) engines by numerical analysis. The baseline engine is a 4-cylinder diesel engine. NG and ethanol fuels are injected into the intake port, while diesel fuel is injected directly into the cylinder. The simulation is performed using GT-Power software, and the results are validated using experimental data. The engine speeds are set at 1000, 1800, and 2800 rpm. The engine loads are set at 50% and 75%. The diesel injection ratios are 10% and 20%. The ethanol substitution rate (ESR) varies from 0% to 60% with an interval of 10%. The results indicate that combustion and emissions are improved with the increase in ESR. First, the engine knock is reduced since the maximum pressure rise rate (MPRR) decreases. Second, the power performance and economy performance of the NDDF engine is improved because the indicated thermal efficiency (ITE) and brake mean effective pressure (BMEP) increase. In addition, although the emissions of the NG-ethanol-diesel ternary-fuel engine are higher than that of NDDF engines, some emissions, such as nitrogen oxide (NOx) emissions and carbon monoxide (CO) emissions, are lower than that of pure diesel engines. This suggests that the addition of ethanol can improve the power and economic performance of NDDF engines.

Способ малоинвазивной транслокации организовавшегося субфовеального кровоизлияния

Purpose. To present a method of minimally invasive surgery, including two-port 27G surgery with controlled administration of a solution of recombinant prourokinase in a patient with organized submacular hemorrhage (SMH). Material and methods. A patient with SMH lasting for 30 days underwent a procedure developed on the basis of the N.I. Pirogov National Medical Surgical Center. It's a minimally invasive technique that includes a two-port 27G access without vitrectomy with controlled administration of a solution of recombinant prourokinase 500 ME through a 38G cannula subretinally, followed by tamponade of the vitreal cavity with a 20 % gasair mixture of hexafluoroethane C2F6. A standard ophthalmological examination was performed before the start of treatment, on the 1st day, 2 weeks later, 6 months after vitreoretinal intervention. Results. Visual acuity was 0.1 at the initial examination and 0.05 upon admission to the surgical hospital. Follow-up showed an increase in visual function to 0.3 at 1 month and to 0.5 at 6 months with antivasoproliferative therapy. According to optical coherence tomography at the initial examination, the central retinal thickness (CRT) was 642 µm, followed by a depression of up to 451 µm by the time of hospitalization. On the 14th day, the decrease in CRT reached 267 µm with complete translocation of the hemorrhage and 243 µm after 6 months. The height of detachment of the retinal pigment epithelium at the initial examination showed a value of 167 µm, and at subsequent observation it was 45 µm, 38 µm and 12 µm on the 1st, 14th day and after 6 months, respectively. Against the background of anatomical results, there was a decrease in the zone of absolute scotoma from 25 loci at the time of admission to 3 loci after 6 months, and an increase in total photosensitivity from 4.5 dB to 15.6 dB, respectively. Conclusion. The use of a minimally invasive method for the treatment of SMH, including subretinal administration of tissue plasminogen activator without vitrectomy with gas-air tamponade, improves morphological and functional prognosis. However, further study of the proposed technique on long-term hemorrhages is required. Keywords: submacular hemorrhage, tissue plasminogen activator, pneumodislocation

Способ проветривания добычных участков калийных рудников Верхнекамья, обеспечивающий безопасность при возникновении аварийной ситуации

The potash mines of the Verkhnekamsk potassium-magnesium salt deposit have low aerodynamic resistance, and therefore many factors influence the air distribution between the mine workings of the mining sites. Some of such significant factors are: the magnitude and direction of the natural draft that occurs between the mine workings due to the difference in air densities in them. The density of air also changes when the temperature changes and when it is mixed with other gases of a different density. When the air is heated, which can be caused by the operation of mining equipment, as well as when an air-gas mixture enters the air (methane is the most common gas in the potash mines of the Verkhnekamsk potassium-magnesium salt deposit), it becomes lighter. In this regard, in the inclined workings, it tends to rise up. In the existing ventilation methods, such a phenomenon has a positive effect in blocks and panels located along the rise of the formation, and a negative effect, when natural drafts prevent ventilation in the production areas located along the dip of the formation. In this regard, it was proposed to change the method of ventilation of mining areas located along the dip of the formation. In the event of a fire in a conveyor mine working, which is the most common fire hazard emergency, due to air heating, natural draughts will begin to play a dominant role in the distribution of air and the spread of flue gases. The article presents the proposed method of ventilation of the mining area of the Verkhnekamsk potassium-magnesium salt deposit of the potash mine, which will allow to efficiently carry out ventilation in the normal mode and prevent the ingress of flue gases into the working area in the event of a fire in the conveyor mine working. This effect is achieved through the positive use of emerging natural drafts and insulating devices (quickly assembled ventilation stoppings). The calculation presented in the article, performed in the «Aeroset» software package, confirmed the assumptions about the efficiency of the proposed solutions.

Отдаленные результаты применения вискодиссекции с контрастированием в хирургии пролиферативной диабетической ретинопатии

Purpose. To evaluate long-term results of surgery for proliferative diabetic retinopathy using contrast-enhanced viscodissection. Material and methods.The study involved 30 patients with type 1 diabetes mellitus (DM) and PDR with traction retinal detachment (TRD). All patients were divided into two groups. In the main group, viscodissection with contrast was performed; in the control group, segmentation and membrane removal were performed using a vitreotome and endovitreal forceps. The observation period was 12 months. Results. During dynamic observation, all patients showed a positive dynamics of morphofunctional parameters. In patients of the control group, in the vast majority of cases, it was necessary to resort to tamponade with silicone oil (60%) or gasair mixture (33%), while in the main group, the main postoperative media were sterile BSS solution (73%) and gas-air mixture (27%). 60% of patients in the control group required a reoperation to remove silicone oil. In patients of the control group in the late postoperative period, IOP values were significantly higher (main group 14.3 ± 1.1; control group 18.7 ± 1.5; p < 0.05), and late postoperative vitreous hemorrhage developed more often (2.3 ± 0.5 in the main group, 4.1 ± 0.6 in the control group; p < 0.05). Conclusion. In the long-term follow-up, the use of this method reduces the need for repeated endovitreal intervention, reduces the risk of developing late postoperative vitreous hemorrhage, and has a positive effect on IOP by reducing the need for endotamponade with silicone oil. Keywords: diabetes mellitus, proliferative diabetic retinopathy, vitreoretinal surgery, contrastenhanced viscodissection

Sensing Characterization of Metal Oxide Semiconductor-Based Sensor Arrays for Gas Mixtures in Air

Micro-electronic gas sensor devices were developed for the detection of carbon monoxide (CO), nitrogen oxides (NOx), ammonia (NH3), and formaldehyde (HCHO), as well as binary mixed-gas systems. Four gas sensing materials for different target gases, Pd-SnO2 for CO, In2O3 for NOx, Ru-WO3 for NH3, and SnO2-ZnO for HCHO, were synthesized using a sol-gel method, and sensor devices were then fabricated using a micro sensor platform. The gas sensing behavior and sensor response to the gas mixture were examined for six mixed gas systems using the experimental data in MEMS gas sensor arrays in sole gases and their mixtures. The gas sensing behavior with the mixed gas system suggests that specific adsorption and selective activation of the adsorption sites might occur in gas mixtures, and allow selectivity for the adsorption of a particular gas. The careful pattern recognition of sensing data obtained by the sensor array made it possible to distinguish a gas species from a gas mixture and to measure its concentration.