Experimental Samples Research Articles

К вопросу целесообразности использования аквапоники как эффективного ресурса для производства объектов аквакультуры и микрозелени

Modern realities, in particular the need to expand import substitution, contribute to the development of new or alternative ways to ensure food security in the Russian Federation. In this regard, the expediency of using aquaponic systems for the cultivation of hydrobionts and various types of micro-plants is being considered. The results of monitoring the hydrochemical regime indicate a decrease in the concentration of ammonia-ammonium, nitrate nitrites relative to the content of the same forms of nitrogen in fish tanks without the use of aquaponics by 1.9; 2.2 and 1.6 times, respectively, which had a beneficial effect on the size and weight indicators of farmed fish. The average mass of tilapia Nile specimens cultivated in the aquaponic system, as well as the absolute growth rate of individuals, exceeded similar indicators of the control group by 1.5 and 1.7 times, respectively. The fish belonging to the experimental group were also characterized by the largest body length relative to the specimens of the control population. The duration of the growing season of microgreens, depending on the culture, ranged from 13 to 25 days. Various types and hybrid forms of basil were characterized by the highest green mass, number of leaves, height, development of the root system and a shorter growing cycle relative to other experimental plant samples (arugula and watercress). The conducted research indicates a high adaptation of this crop to existence in aquaponics conditions, therefore it must be considered as one of the key ones for this type of cultivation. The results obtained allow us to recommend the use of joint cultivation of microgreens and aquatic organisms as a resource for increasing the economic efficiency of industrial systems of aquaculture farms.

In Situ, High-Resolution Quantification of CO2 Uptake Rates via Automated Off-Gas Analysis Illuminates Carbon Uptake Dynamics in Cyanobacterial Cultures.

Quantification of cyanobacterial CO2 fixation rates is vital to determining their potential as industrial strains in a circular bioeconomy. Currently, however, CO2 fixation rates are most often determined through indirect and/or low-resolution methods, resulting in an incomplete picture of both dynamic behaviors and total carbon fixation potential. To address this, we developed the "Automated Carbon and CO2 Experimental Sampling System" (ACCESS); a low-cost system for in situ off-gas analysis that supports the automated acquisition of high-resolution volumetric CO2 uptake rates from multiple cyanobacterial cultures in parallel. Carbon fixation data obtained via ACCESS were first independently validated by elemental analysis of cultivated biomass. Using ACCESS, we then demonstrate how the volumetric CO2 uptake rate of two model cyanobacteria, Synechococcus sp. PCC 7002 and Synechocystis sp. PCC 6803, accelerates linearly to a maximum before then decaying monotonically to cessation by stationary phase. Furthermore, consistent with the expected stoichiometry, strong correlations were also found to exist between cell growth and carbon fixation, both in terms of rates as well as total levels. The novel insights made possible via ACCESS will aid other cyanobacterial researchers in diverse fundamental and applied research efforts.

Experimental, Numerical and Analytical Evaluation of Load-Bearing Capacity of Cold-Formed S-Beam with Sectional Transverse Strengthening

The article provides information about strengthening cold-formed thin-walled steel beams made of the sigma profile. An innovative concept for sectional transverse strengthening of thin-walled beams subjected to concentrated forces was investigated. The proposed solution’s novelty lies in attaching the sectional transverse strengthening to the beam’s cross-section, employing a point crimping technique. This technique requires a specific modification of the cross-section edges, necessitating double-lipped flanges. This strengthening method is innovative, as it has not been previously applied to cold-formed structures. Typically, strengthening is achieved using other cold-formed elements or materials, such as timber, lightweight concrete, or CFRP tapes. The laboratory experimentally validated the proposed method using short- and medium-length beams. The experimental results were then compared with the results of the numerical analyses and the conventional design approach described in EC3. The results demonstrated the feasibility of implementing this type of strengthening, its reliability under load, and the confirmation of an increase in the load-bearing capacity of the experimental samples by 11–24%.

Влияние на СО2 емисия от птицеферма върху микроелементния състав на отглеждана в оранжерия маруля (Lactuca sativa)

The aim of the present study was to evaluate the effect of increased CO2 l evels a s a c ompound of mixed emissions from a poultry housing (transported by an air duct into a greenhouse), on lettuce’ trace elements content. The experiment was carried out at the experimental poultry farm of the Institute of Animal Science - Kostinbrod in May and June, 2019, for 40 days. During the experiment the following parameters were controlled and measured both in control and experimental greenhouses (lettuce groups): average level of CO2, indoor air temperature and relative humidity, - three times a week during irrigation at noon by handset IAQ Monitor SM-2100; Average level of ammonia (NH3) - three times a week during irrigation at noon by handset Aeroqual Series 200 Monitor. At the end of the experiment, soil and plants samples from both groups were taken and tested for the content of 15 microelements - Vanadium (V), Chromium (Cr), Manganese (Mn), Cobalt (Co), Nickel (Ni), Copper (Cu) , Zinc (Zn), Arsenic (As), Selenium (Se), Molybdenum (Mo), Silver (Ag), Cadmium (Cd), Tin (Sn), Mercury (Hg) and Lead (Pb) by mass spectrometry with inductively coupled plasma (ICP-MS). The obtained results show that the triple increase in the cobalt concentration in the experimental group (P <0.001) can definitely be associated with the increased photosynthesis and the expected Vit. B12 levels. Of interest are also the levels of the elements vanadium and chromium – respectively, 3.3 and 10.7 times higher in the experimental group compared to the control group (P <0.001). The content of copper and selenium in the plants corresponds to their high level in the soil, but in copper the accumulation in the experimental group is suppressed (P <0.01), while for selenium we can assume that CO2 stimulates to some extent its accumulation (P <0.05).

Исследование гидрофильности поверхности металлических материалов, модифицированных ультрафиолетовым лазерным излучением

Introduction. Surface modification using laser radiation is a promising direction in the field of creating new technologies for treatment metal materials, including those for medical purposes. The ability of lasers to change the surface characteristics of a material and, consequently, its interaction with the environment has attracted great interest among researchers. Despite numerous recommendations for the use of laser surface treatment, there is still lack of systematic and detailed studies on the influence of parameters on the structural-phase state and properties of the modified surface, especially concerning ultraviolet laser exposure. The purpose of this work is to study the hydrophilicity of the surface of TiNi alloy and stainless steel after UV laser treatment. Materials and methods of the study: experimental samples made of TiNi (TN-10) alloy and 12KH18N9T (AISI 321) stainless steel were locally (beam diameter 0.5 cm) exposed to a solid-state Nd:YAG laser at the wavelength of 266 nm, with a pulse duration of ~ 5 ns, and pulse repetition rate of 10 Hz. The material was exposed to a constant output radiation energy density of 0.1 J/cm2, with a change in the exposure duration from 10 to 600 s. Before and after UV laser treatment, the wettability of the material surface and free surface energy were determined. The structure, elemental and phase composition, and surface topography of TiNi and steel were studied using scanning electron microscopy with the determination of the elemental composition by energy-dispersive spectroscopy, X-ray phase analysis, and profilometry. Results and discussion. Ultraviolet laser treatment of the surface of TiNi alloy and steel samples leads to an increase in their hydrophilicity. In the initial state, the contact angle of wetting is ≈75° for both materials, and after ultraviolet laser treatment it decreases to ≈11-13° for TiNi and to ≈22° for steel. The phase composition of steel does not change during laser treatment, and phases belonging to oxides are recorded on the surface of TiNi after 420 seconds of treatment. Ultraviolet laser treatment of TiNi alloy and steel leads to an increase in free surface energy, a change in the ratio of its components (a decrease in the dispersed component and a significant increase in the polar component), an increase in the oxygen content on the surface of both materials. With long laser exposure times (more than 300 seconds), microcracking occurs on the surface of the processed material, leading to an increase in roughness. The change in the surface topography (roughness) of TiNi alloy does not have a noticeable effect on the wettability of the surface of metal materials, and for steel samples, there is an insignificant tendency to reduce the contact wetting angle with increasing roughness. The degree of hydrophilicity of metal materials, characterized by the contact wetting angle, increases with an increase in the duration of laser exposure due to saturation of the surface with free oxygen and an increase in free surface energy (its polar component). Based on the studies, it can be concluded that ultraviolet laser treatment is an effective way to change the wettability of metal materials.

Decoding Age-Related Changes in Emotional Reactivity: The Importance of Distinguishing Positive and Negative Sensations

This study investigated age-related variations in emotional reactivity, focusing on the differentiation between positive and negative emotional sensations. Grounded in Socioemotional Selectivity Theory (SST), we hypothesized that older vs. younger adults would exhibit heightened valence and intensity in their emotional sensations, alongside increased co-occurrence of positive and negative sensations. We presented 100 negative, 100 neutral, and 100 positive images to 67 young adults and 72 older adults. Utilizing unipolar scales enabled a nuanced analysis of emotional reactivity. Our findings revealed that older vs. younger adults overall report: 1) more positive and negative sensations, with a predominance for positive sensations, particularly when faced with positive images; 2) more intense sensations, regardless of the valence of the images; 3) more complex emotional sensations, particularly when faced with negative images. Thus, our findings validated the key principles of SST and can be seen as a manifestation of an adaptive strategy developed in older adults to promote richer, more positive emotional experiences. However, the study’s broader implications are moderated by certain limitations. The experimental sample shows a gender imbalance, with a predominance of females and a lack of racial, ethnic and socio-economic diversity in older adults. In addition, the low- to medium-intensity emotional stimuli reflect only a narrow spectrum of everyday experiences. These constraints underscore the need for future research to encompass greater demographic inclusion and a wider range of emotional stimuli to ensure the applicability of our findings to more complex populations and emotional landscapes.

THE ROLE OF ORGANIC COMPLEXES OF MINERAL ELEMENTS IN THE METABOLISM OF RUMINANT RUMEN

Introduction. Trace elements are elements necessary for the body in negligible amounts, in particular for ruminants from 0.10 to 50.0 mg per kg of dry matter in the diet. All these trace elements are necessary for the biochemical processes of the body, which maintain the normal state of metabolism in the body, contribute to maintaining health and increasing productivity. Ensuring sufficient minerals is a particularly difficult task, since the needs for most minerals are not constant, but depend on physiological factors, including genetics, age, gender, type of production and level of production, and also depends on the composition and quality of the diet. The aim – this article examines the effect of organic forms of mineral additives on metabolism and the degree of digestibility of the dry matter of the feed substrate in the rumen. Material and methods. To implement the tasks set, 4 samples were formed – a control and 3 experimental (I, II, III). All samples were presented with wheat bran, however, before incubation, mineral complexes were introduced into the working tanks where the experimental samples were located: I – Co + Fe; II – Se+Zn; III – Cu. As mineral preparations, the following were used: copper bioplex – 10 mg/kg CB  (manufacturer: Alltech, Serbia), zinc bioplex – 140 mg/kg CB (manufacturer: Alltech, 54 Ltd, Ireland); selenium-plex – 0.1 mg/kg CB (manufacturer: Alltech flanders BVBA, Belgium); cobalt chloride – 0.1 mg/kg CB (manufacturer: NPK Ascont+ LLC, Moscow region, Russia); iron chelate – 50 mg/kg SV (manufacturer GLS PHARMACEUTICALS, Moscow, Russia). Studies of the digestibility of the studied feed substrate were carried out by the in vitro method according to a specialized technique. The level of volatile fatty acids (VFA) in the contents of the scar was determined by gas chromatography on a gas chromatograph "Crystallux-4000M", determination of nitrogen forms according to GOST 26180-84. Results. The use of Cu, Co+Fe, Se+Zn contributes to an increase in the digestibility of the CB feed substrate by 1.0–2.4% (p < 0.05), an increase in the concentration of nitrogen in the scar fluid and maintenance of pH at the level of 6.7–6.8. Conclusion. The use of various mineral complexes in the feeding of ruminants contributes to a change in the course of metabolic processes in the rumen.

Biodegradation and Thermomechanical Behavior of 3D-Printed PLA Scaffolds Under Static and Stirring Biomimetic Conditions

3D-printed biomedical polylactic acid (PLA) scaffolds were developed, and their biodegradation, as well as their thermomechanical behavior, were studied in a relevant in vitro environment. The scaffold’s biodegradability profile has been monitored after immersion in a cell culture medium that contains components of blood and body fluids. Two types of biodegradation experiments were performed—a standard static one and an adapted stirring one, mimicking the body fluids’ flow, respectively—to achieve a comparative investigation. The biodegradation experiment’s duration was one month. The measurements were performed between days 1 and 28. The scaffold microstructure was analyzed with scanning electron microscopy (SEM). The weight loss of the scaffolds has been monitored. Differential scanning calorimetry (DSC) has been used to evaluate the glass transition temperature (Tg) of the scaffolds and to draw useful conclusions about their thermal behavior. Finally, dynamic mechanical analysis (DMA) was applied to investigate the viscoelastic behavior of the samples. The SEM analysis demonstrated that the samples in a static experiment are more damaged, while those in the stirring experiment are more brittle. The maximum Tg value of the material measured by DSC is around 65 °C. This value is reached after 5 days of immersion in static conditions and after 14 days of immersion after stirring, indicating that some processes take place faster in the static experiment. The variation of the Tg vs. immersion time, as derived from DSC vs. DMA measurements, gives similar results for both static and fluid absorption conditions, demonstrating the reproducibility of the results.

Detection and Pathogenicity Features of Pseudomonas Aeruginosa in Patients with Skin Infection

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen often concerning studies in bacterial resistance and pathogenicity. Nosocomial infections from burns and surgical site infections are often caused by destruction of the natural defenses of the skin, exposed matrix proteins and inflammatory factors being compromised making it easier for P. aeruginosa to colonize the area leading to infection. For this experiment, 113 wound and burn samples collected from hospitalized immunocompromised patients. 26 isolates tested positive for P. aeruginosa with associated virulence factors. Identification of bacteria concluded biochemical assays, antibiotics susceptibility, and the ability of biofilm formation and the presence of P.aeruginosa in different skin samples. The study showed 66.53% of the isolates were resistant to antibiotics including (AK, GN, IPM, LEV, CIP, ATM, PRL and TZP), while prevalence of sensitivity was to Meropenem (65.38%) and Cefepime (19.23%). Biofilm formation assay showed all P.aeruginosa isolates formed biofilms at different levels (65.3%) weak (27%) moderate and (7.7%) strong biofilm formation. Following the study's conclusion, consider specific strategies for managing and shielding future generations against P.aeruginosa bacterial infections.

DEVELOPMENT OF REFRACTORY CONCRETE USING GLASS GRINDING WASTE SAND

This study investigates the utilization of glass grinding waste sand as an alternative fine aggregate in the formation of refractory concrete. Experimental refractory-concrete samples were subjected to sintering at 1200 °C, followed by a comprehensive evaluation of their physical and mechanical properties. The parameters assessed included flexural strength, volume density, shrinkage/expansion behavior upon drying and firing, thermal shock resistance, and thermal conductivity, following Vietnamese standards. Additionally, the mineral composition was determined using X-ray diffraction, while the microstructural characteristics were analyzed via scanning electron microscopy. Experimental findings indicate that incorporating 5 wt.% of glass grinding waste sand enhances the degree of sintering in refractory concrete at elevated temperatures while maintaining its essential refractory properties. The XRD analysis revealed the presence of α-Al2O3 and γ-Al2O3 phases, contributing to the refractory concrete’s improved heat resistance and thermal shock resistance. The SEM analysis corroborated these findings by illustrating the microstructural modifications imparted by the glass grinding waste sand. Incorporating glass grinding waste sand at an optimal concentration of 5 w/% promotes sintering at high temperatures and preserves the critical refractory characteristics of concrete. This study underscores the potential of glass grinding waste sand as a viable alternative fine aggregate for refractory concrete, contributing to material sustainability and performance improvement.

Study on the thermal hazards of anionic surfactant AES on lignite via experiments and calculations

Spray dust reduction is a commonly used dust reduction method in coal mines and has been widely adopted. However, the thermal stability of coal dust after being wetted by dust suppressants remains unknown. The work aimed to investigate the potential environmental hazards posed by the secondary dust dispersion resulting from the cracking of lump coal dust after being wetted by surfactants and subsequently air-dried. Lignite and AES were used as experimental samples. Use thermodynamic equations to analyze, calculate, and compare the changes in the average apparent activation energy of lignite before and after AES solution wetting. Compared with lignite before AES solution wetting, the combustion characteristic index of lignite decreased by 1.93 % after wetting, and before and after AES solution wetting, the average apparent activation energy of lignite calculated by reaction kinetics methods decreased by 7.6 %, 6.7 %, and 17.1 % respectively. FTIR analysis shows the proportion of aliphatic hydrocarbons in lignite after AES solution wetting has decreased compared with before wetting, and the proportion of oxygen-containing functional groups has shown an upward trend. The work elucidated the complex microscopic mechanisms underlying hazards caused by secondary dust dispersion, providing new scientific evidence for preventing and controlling coal dust explosion accidents.

Evaluation of the qualitative performance indicators of the experimental OVX-600 sprayer with a pneumatic disk system

Abstract The article presents the results of field experiments to determine the quality of cotton processing with an experimental OVX-600 sprayer with a pneumatic disk sprayer in the mode of a low-volume spraying method with a working fluid consumption of 50-100 l/ha. During the field research, a nomogram was compiled to determine the flow rate of working fluid for low-volume spraying, regardless of the type of tractor and at various speed modes of the unit. The results of high-quality processing of cotton with an experimental OVX-600 sprayer with a pneumatic disk sprayer were obtained, which showed that with a capture width of up to 21.6 meters, the deposition of the drug, both in the width of the capture (45.9%) and in the height of the bush (68.1%) of cotton meets agrotechnical requirements. The conducted field experiments have shown that by the density of the coating of the surface of the cotton leaves, and by the dispersion of droplets (80-120 microns), the experimental sample of the OVX-600 sprayer with a pneumatic disk sprayer is quite suitable for use in the mode of low-volume spraying of cotton.

Manifestarea comportamentului în trafic în raport cu experiența de șofat

Aggression in traffic is a widely researched topic with numerous factors identified as contributors to aggressive behavior. The purpose of the research is to highlight the manifestation of risk-taking, aggressiveness and the need for thrills in relation to the drivers’ driving experience. The experimental sample consisted of 149 male and female drivers aged 18-60. The results indicate that the predisposition to risk is more pronounced among drivers with longer driving experience (5-10 years; 10-15 years). The manifestation of physical aggression and the use of the vehicle to express aggression at an average level, is characteristic for the groups of drivers with longer driving experience (5-15 years) than for the novice group, up to 5 years. Beginner car drivers adopt a high level of manifestation of the constructive expression of aggression, adopting cognitive and behavioral strategies to avoid conflict situations in traffic.

Potential therapeutic and ameliorative effects of ramipril alone and in combination with methylprednisolone for the cytokine releasing syndrome in mice: An in vivo study.

Cytokine-releasing syndrome (CRS) is a special form of systemic inflammatory response syndrome provoked by factors like viral infections and certain immunomodulatory drugs like monoclonal antibodies and adoptive T therapy. To elucidate the potential role of ramipril (RM) and its combination with methylprednisolone (MP) against the development and progression of CRS in mice. This experiment consists of two parts: protective and therapeutic interventions. The protective experiment: in the induction group, mice received an intraperitoneal injection (IP) of 5mg/kg lipopolysaccharide (LPS) without intervention. The other groups received various drugs before the induction by three days, then observed for an additional two days (50 mg/kg MP, 3 mg/kg RM, and a combination of 1.5 mg/kg RM with 25 mg/kg MP). The second part of the study involves the therapeutic potential; all groups received similar doses of drugs in the prevention groups, except LPS induction was given first, and after one hour, the mice received daily doses of the drugs for five days. At the end of the experiment, blood and tissue samples were obtained. Mice treated with RM and its combination with MP showed improved serum TNF-α, IL-6, IL-8, IL-1β, INF-γ, MDA, and GSH in both prevention and therapeutic groups. Histopathologically, mice treated with ramipril and its combination with MP ameliorate the tissue damage in both lung and liver tissues following LPS induction. Ramipril showed protective and therapeutic effects in LPS-induced cytokine storms in mice through anti-inflammatory and antioxidant mechanisms.

Relationships Between Cognitive Impairments and Motor Learning After Stroke: A Scoping Review.

Stroke is one of the leading causes of chronic disability worldwide. Sensorimotor recovery relies on principles of motor learning for the improvement of movement and sensorimotor function after stroke. Motor learning engages several cognitive processes to effectively learn and retain new motor skills. However, cognitive impairments are common and often coexist with motor impairments after stroke. The specific relationships between poststroke cognitive impairments and motor learning have not been determined. To summarize the existing evidence related to cognitive impairments and motor learning after stroke. Specific goals were to determine: (1) how motor learning is studied in individuals with poststroke cognitive impairments; (2) how cognitive impairments are assessed; (3) which cognitive domains impact motor learning. Over 400 studies were screened for specific inclusion criteria and 19 studies that related poststroke cognitive impairments to motor learning were included. Studies used a wide variety of experimental designs, sample sizes, and measures for cognitive evaluation. Cognitive impairments impacting motor improvement and learning capacity after stroke were reported in all but 4 studies. The most common domains impacting motor learning were attention, executive function, and memory. Detailed cognitive assessments, retention testing, and a combination of clinical and kinematic outcomes are recommended for future studies. The presence of specific cognitive impairments measured with sensitive instruments should be considered when designing effective training interventions for patients with stroke to maximize sensorimotor recovery.

АСИНХРОННІ ГЕНЕРАТОРИ В АВТОНОМНИХ ДЖЕРЕЛАХ ЖИВЛЕННЯ ЗВАРЮВАЛЬНОЇ ДУГИ. СТАН І ПЕРСПЕКТИВИ

The article is aimed at generalizing the results of the study of asynchronous generators (AG) of autonomous welding arc power sources (AWPS) obtained in the Department of Electromechanical Systems of the Institute of Electrodynamics of the NASU. The proposed classification of AG of autonomous welding systems is considered, mathematical models are developed, the results of computational and experimental studies of such systems with AG with capacitor excitation and an uncontrolled rectifier, in the DC circuit of which high-frequency inverters, pulse-width regulators or half-bridge inverters are connected, as well as generators with valve and valve-capacitor excitation. The design features and experimental samples of welding arc power sources with AG are considered. The directions of further research are determined. Ref. 42, fig. 5.

Underwater Drag Reduction Failure of Superhydrophobic Surface Caused by Adhering Spherical Air Bubbles

Underwater drag reduction using superhydrophobic surfaces is a promising method due to its simplicity and low energy consumption. However, most attempts to obtain drag reduction using superhydrophobic surfaces have failed. Explanations such as air layer or air bubble vanishment and surface roughness are proposed in the existing works. In this work, the drag increase caused by spherical air bubbles adhering to the superhydrophobic surface is reported, and the drag increase mechanism is revealed by numerical simulation. In the water tunnel and towing tank experiment, we found that the experimental samples exhibited drag increase around a specific velocity, and the recorded optical images showed that the superhydrophobic surfaces were adhered by spherical air bubbles. Through numerical simulation, we found that the spherical air bubbles not only reduced the frictional drag but also introduced pressure drag. The drag increase was produced when the introduced pressure drag exceeded the reduced frictional drag. This work might be helpful for the drag reduction application of the superhydrophobic surface.

The development of the technology of a thick extract for the treatment of cheilitis

Aim. To substantiate the parameters of the technological process for obtaining an aqueous thick extract based on the medicinal plant raw material for the treatment of cheilitis. Materials and methods. The study objects were experimental samples of a phytocomplex (large burdock root: oak bark: pot marigold flower buds 5: 1: 1.5) and an aqueous thick extract obtained on its basis. During the development of the technology for obtaining a thick extract and its standardization, organoleptic, physicochemical and pharmacotechnological research methods were used in accordance with the methods and recommendations given in the SPhU 2.0. The results of the research were statistically processed in accordance with the requirements of monograph 5.3 of the SPhU 2.3. Results. The pharmacotechnological properties of the phytocomplex for the prevention and treatment of cheilitis – large burdock root: oak bark: pot marigold flower buds (5: 1: 1.5, respectively) were experimentally studied. The optimal conditions for extraction of the complex with purified water were determined; they were: temperature – 95-100 ºС; three-stage remaceration method; the total ratio of the raw material: finished extract (1:10). The technological parameters were worked out; the technological flowsheet of the process for obtaining an intermediate product – an aqueous thick extract under the conditional name “Phytol” was developed. Conclusions. Based on the studies conducted, the technological parameters of the extraction process for the phytocomplex proposed have been determined; the technology for obtaining an aqueous thick extract has been substantiated step-by-step, and its technological flowsheet has been drawn up.

Pool boiling on the aluminum alloy, copper and WC-coated copper with micro-finned textures and developed multimodal roughness formed by nanosecond laser radiation

Boiling remains one of the most effective processes allowing heat to be removed from heat-loaded surfaces of technological equipment. Due to the development of technologies for metal surface treatment with laser radiation to form specified near-surface properties, including the type, texture configuration and wetting properties, the task of substantiating the use of heat transfer surfaces modified by laser radiation to intensify the boiling process has become relevant. The pool boiling characteristics in distilled degassed water (before the boiling crisis onset) were compared experimentally on the surfaces of samples made of aluminum alloy, copper, and WC-coated copper. Experimental samples were treated by two different methods, including widely used polishing with abrasive materials and laser radiation. Nanosecond laser treatment was used to make micro-finned and anisotropic (developed hierarchical roughness) textures. Textured samples were then hydrophobized. As part of the experiments on pool boiling, the characteristics of the forming bubbles were recorded on the prepared surfaces, heat transfer coefficients, and critical heat flux values were determined. Experimental results were compared with predicted characteristics using well-known models. The evolution of the functional properties of laser-textured metal surfaces after prolonged exposure to heat flux, which is typical of the operating modes of modern heat-loaded equipment, was assessed.

Study of morphology, phase composition, optical properties, and thermal stability of hydrothermal zirconium dioxide synthesized at low temperatures.

Oxide nanoparticles exhibit unique features such as high surface area, enhanced catalytic activity, and tunable optical and electrical properties, making them valuable to various industry applications as well as for the development of new research projects. Nowadays, ZrO2 nanoparticles are widely used as catalysts and precursors in ceramic technology. Hydrothermal synthesis with metal salts is one of the most common methods for producing stable tetragonal-phase zirconium dioxide nanoparticles. However, hydrothermal synthesis requires relatively high process temperatures (160-200°C) and the use of advanced heat-resistant autoclaves capable of maintaining high pressure. This paper investigates how different precursors (ZrOCl₂·8H₂O and ZrO(NO₃)₂·2H₂O) and synthesis temperatures (110-160°C) affect the phase composition, optical properties, size, and shape of ZrO₂ nanoparticles produced by hydrothermal synthesis without calcination. In addition, the effect of temperature exposure in the range of 100-1000°C on the phase stability of the synthesized nanoparticles was studied. X-ray diffraction and Raman spectroscopy techniques were used to determine the structure and phase composition, while the optical properties were examined through the analysis of transmission and absorption spectra in the visible and UV ranges. It was found that the obtained particles at synthesis temperatures of 110-130°C have predominantly cubic c-ZrO2 phase, which changes to monoclinic phase when heated above 500°C. Analysis of visible and UV spectroscopy data reveals that the experimental samples have pronounced absorption in the middle UV range (200-260nm) and have an energy band gap Eg varying from 4.8 to 5.1eV. The hydrothermal powders synthesized in this study can be used as absorbers in the mid-UV range and as reinforcing additives in the preparation of technical ceramics.