Final Temperature Research Articles

Preparation of reversible temperature sensitive acrylamide terpolymer hydrogel for cascade drug loadings

As a drug delivery system with vast potential applications, hydrogels have garnered significant attention due to their unique drug loading mechanisms and effectiveness. In this paper, a novel reversible thermosensitive hydrogel polymer, synthesized through copolymerization of mono-6-allyl-β-cyclodextrin, N-isopropylacrylamide, and acrylamide, is introduced. This hydrogel polymer formed a three-dimensional network structure in water, featuring β-cyclodextrin hydrophobic cavities. The encapsulated drug molecules could be slowly and progressively released from both the three-dimensional network and the β-cyclodextrin hydrophobic cavities. IR and XRD analysis confirmed the successful encapsulation of the target drug molecules, sodium salicylate and naproxen sodium, within the β-cyclodextrin cavity of the hydrogel polymer and its three-dimensional network space. Specifically, when the mass ratio of N-isopropylacrylamide/acrylamide/mono-6-allyl-β-cyclodextrin was 9.8/0.2/0.5, the polymer hydrogel demonstrated an initial gelation temperature of 34.9 °C and a final gelation temperature of 37 °C. The expansion rate of the blank hydrogel was slightly higher than that of the drug-loaded hydrogel. Both drugs undergo sustained release through the hydrogel, adhering to Fick’s diffusion law, ensuring consistent drug release within 8 h and maintaining this release for over 24 h, regardless of the drug loading rate. Within 30 days, the degradation rate of the drug-loaded hydrogels in PBS exceeded 15%, while the degradation rate in the presence of lysozyme was more than 40%. These properties render the hydrogel a versatile candidate for targeted drug delivery and biomedical applications, offering novel strategies for treating chronic diseases and other conditions.

Microstructure and Thermal Cyclic Behavior of FeNiCoAlTaB High-Entropy Alloy.

This study investigates the grain morphology, microstructure, magnetic properties and shape memory properties of an Fe41.265Ni28.2Co17Al11Ta2.5B0.04 (at%) high-entropy alloy (HEA) cold-rolled to 98%. The EBSD results show that the texture intensities of the samples annealed at 1300 °C for 0.5 or 1 h are 2.45 and 2.82, respectively. This indicates that both samples were formed without any strong texture. The grain morphology results show that the grain size increased from 356.8 to 504.6 μm when the annealing time was increased from 0.5 to 1 h. The large grain size improved the recoverable strain due to a reduction in the grain constraint. As a result, annealing was carried out at 1300 °C/1 h for the remainder of the study. The hardness decreased at 24 h, then increased again at 48 h; this phenomenon was related to the austenite finish temperature. Thermo-magnetic analysis revealed that the austenite finish temperature increased when the samples were aged at 600 °C for between 12 and 24 h. When the aging time was prolonged to 48 h, the austenite finish temperature value decreased. X-ray diffraction (XRD) demonstrated that the peak of the precipitates emerged and intensified when the aging time was increased from 12 to 24 h at 600 °C. From the three-point bending shape memory test, the samples aged at 600 °C for 12 and 24 h had maximum recoverable strains of 2% and 3.6%, respectively. The stress-temperature slopes of the austenite finish temperature were 10.3 MPa/°C for 12 h and 6 MPa/°C for 24 h, respectively. Higher slope values correspond to lower recoverable strains.

Molecular dynamic simulation study on the influence of heating rate on the thermal decomposition process of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB).

To clarify the effect of heating rate on the thermal decomposition process of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), this study employs molecular dynamic simulations to investigate the thermal decomposition of TATB at heating rates of 20, 40, 60, and 80K/ps. The initial temperature is uniformly set to 300K, while the final temperature is set to 3000K. Results indicate that within the temperature range of 300-3000K, the thermal decomposition rate of TATB decreases with increasing heating rate, whereas the initial decomposition temperature of TATB increases, consistent with the experimental pattern. Within the studied temperature range, a lower heating rate results in a higher number of decomposition fragments, leading to more effective collision between active fragments, facilitating more effective collisions between active species, and leading to the formation of more stable products such as H₂O, CO₂, and N₂. Conversely, higher heating rates reduce the quantities of these stable products. This study enhances the understanding of TATB's thermal decomposition mechanism, providing valuable insights for its safe handling and application. METHODS: The Gaussian09 software was used to calculate the BDEs of TATB molecules, while the MD simulation using the ReaxFF-lg force field was performed by the LAMMPS package. Visualization and postprocessing were conducted using the OVITO software, and a custom script was developed to analyze the reaction products and frequencies.

Tow-parameter quasi-boundary value method for a backward abstract time-degenerate fractional parabolic problem

Abstract In this article, for a time-degenerate fractional parabolic equation, we study an inverse problem for restoration of the initial condition from the information of the final temperature profile. We show that the considered problem is ill-posed in the sense of Hadamard, i.e., small errors in the measurement data may lead to indefinitely large errors in the solutions. This ill-posed problem is regularized using a modified quasi-boundary value method, and some convergence estimates for the regularized solution are obtained using a priori and posteriori parameter choice rules. Finally, several numerical experiments are presented to demonstrate the accuracy and efficiency of the regularization method.

Development of the structure of a cyberphysical control system for the process of tailored induction heating of a steel billet

The article is devoted to the development of the structure of a cyberphysical control system for the process of zone induction heating, widely used in modern industrial production during the heat treatment of metal products for various purposes. An analysis of the range of products manufactured using induction heat treatment and the advantages of using induction heating systems has shown a wide range of applications of this method of heat treatment in modern production and great opportunities for automation and optimization of processes associated with induction heating of products. This fact indicates the relevance of the development of various kinds of intelligent control systems in relation to the processes of industrial induction heating of metal blanks and semi-finished products. The article describes the induction method of zone heat treatment of metals, its advantages over flame heat treatment methods and the range of products manufactured using it. A description of the billet-inductor system is presented, for which the structure of a cyberphysical control system for the process of zone induction heating has been developed. The technological requirement for the final temperature distribution on the surface of the workpiece and the factors influencing the deviation of the temperature distribution from that required in the process of zone induction heating are considered. A list of possible disturbing influences is given, requirements for the technological process are formulated, control principles are described and, based on this, the structure of the zone induction heating process control system, which belongs to the class of cyberphysical process control systems, is developed.

Microwave and Steam Processing: A Novel Approach to Modifying the Characteristics of Reconstituted Whole Wheat Flour and Dough.

To reduce the adverse effects of bran on whole wheat flour products. In this study, seven reconstituted whole wheat flours were prepared and used to determine the effects of microwave and steam treatment on bran. We aimed to understand the effect of modification treatment on the properties of reconstituted whole wheat flour and dough. Treatment with whole wheat flour had a significant impact on the color, solubility, and swelling. As the cooking time increased, the initial temperature (To), peak temperature (Tp), and final temperature (Tc) of pasting and enthalpy (Hp) decreased. The combination of microwave and steam modification increased water absorption and stabilization time, leading to improved fermentation performance and cooking stability of the dough. The modified whole wheat flour and dough exhibited a significant decrease in crystallinity, possibly due to the degradation of the crystalline and amorphous regions of the starch granules during heat treatment. Upon modification treatment, the spiral β-turn structure was transformed into an irregular curled and β-sheet structure, and the β-sheet ratio increased significantly (p < 0.05). The modification of bran through microwave treatment (700 W for 30 s) followed by steam treatment (10 min) enhanced the processing performance of reconstituted whole wheat flour, offering substantial potential for the development of novel products and the optimization of industrial production efficiency.

Nitinol Reactive Oxygen Assist Gas Laser Micromachining: Demystifying the Implications Imposed Upon Pseudoelasticity and the Shape Memory Effect for Nickel-Titanium Alloys

Herein, a novel investigation examines a long-pulse microsecond laser cutting process with an oxygen assist gas and the subsequent effects on martensitic phase transformations for binary nickel-titanium alloys. To establish a comprehensive comparative analysis, a reactive oxygen assist gas process, a standard inert argon assist gas process, and athermal femtosecond laser micromachining are studied in order to form a complete analytical assessment of how laser processing can inflict implications upon pseudoelasticity and shape memory. In-situ thermography reveals an approximate 1.5-times increase in thermal area for an argon assist gas when compared to oxygen. In conjunction with thermal analysis, electron backscatter diffraction and optical microscopy demonstrates 1.7 to 25 μm of epitaxial grain recrystallization associated with the elevated level of thermal propagation. Low cycle fatigue testing of pseudoelastic performance realizes a 12.7 % decrease in the achievable upper plateau stress when comparing long-pulse cutting to femtosecond cutting. Furthermore, when the laser power exceeds 30 W, the ultimate tensile strength suffers notable reductions of 25 % and 40 % for the oxygen and argon processes respectively when compared to femtosecond micromachining. Bend and free recovery testing provides insights into shape memory performance of the endothermic phase transformation from B19’ martensite to B2 austenite, revealing marginal ∼1.5 ˚C reductions in the active austenite finish (Af) temperature as laser power was increased from 10 W to 60 W. Lastly, long-pulse laser processing results in notable ∼15 ˚C shifts in the austenite start (As) temperature during the reverse martensite phase transformation from B19’→R→B2.

Tribological Behavior of Gas-Nitrided 42CrMo4 Steel at Elevated Temperatures

Nitriding is a well-known thermochemical treatment improving the surface hardness and the wear resistance of steel. The phase composition and growth kinetics of the nitrided layer can be controlled using a gas nitriding with changeable nitriding potential. In this work, such a gas nitriding was used to produce, on 42CrMo4 steel, the two nitrided layers differing in the thickness of compound zone and diffusion zone. The microstructure and nanohardness of these layers were studied. For the first time, the tribological behavior of gas nitrided layers at elevated temperatures (from 23 to 400 °C) was investigated. The compound zone consisted of ε + (ε + γ’) iron nitrides and, in the diffusion zone, the nitric sorbite with γ’ precipitates was observed. The highest nanohardness was measured in the ε + γ’ zone. The lowest values of friction coefficients were obtained if the contact surface of the friction pair entered the ε + γ’ zone. After the wear process, at a final temperature of 400 °C, worn surfaces showed only intensive abrasive wear, evidenced by shallow grooves. The increased oxygen content at the edges of wear tracks indicated possible oxidative wear.

Impact of Soil Type and Moisture Content on Microwave-Assisted Remediation of Hydrocarbon-Contaminated Soil

Volatile and semi-volatile compounds, such as petroleum hydrocarbons and equipment lubricating oils, often contaminate soil due to accidents, posing significant ecological and health risks. Traditional soil remediation methods, such as thermal desorption and bioremediation, are time-consuming and resource-intensive, prompting researchers to explore more efficient alternatives. This study investigates the effectiveness of an in situ reactor for microwave-assisted soil remediation, specifically focusing on the impact of soil type and moisture content on pollutant removal efficiency. The reactor, designed to operate within a modified household microwave oven, provides direct microwave irradiation to the soil surface, enabling precise control of heating conditions. Experiments were conducted using soil samples of varying particle sizes and moisture levels under standardized conditions (1000 W microwave power, 2.45 GHz frequency). The results show that moisture content plays a critical role in pollutant removal efficiency, with an optimal moisture content of 10 wt % enhancing microwave absorption and energy transfer, thus improving pollutant recovery. In comparison with traditional resistive heating, microwave heating achieved a faster temperature rise and higher final temperatures, significantly improving pollutant removal efficiency in a shorter time frame. This study highlights the advantages of microwave heating, including its superior energy efficiency, faster pollutant volatilization, and the potential for optimized soil remediation in real-world applications. These findings provide valuable insights for the development of more sustainable and efficient soil remediation technologies.

Analysis of a Commercial Red Wine Fermentation Dataset with a Wine Kinetic Model

The adoption of sensors to monitor wine fermentation enables the collection of large datasets that relate the initial juice chemistry, density and temperature patterns during fermentation to fermentation outcomes. Wine kinetic models are now being applied to commercial fermentations in real time to identify abnormal or sluggish fermentations. In this work, 222 red wine fermentations from five harvests at two commercial wineries were evaluated by a wine fermentation model. The model parameters, initial juice chemistries and fermentation outcomes were analyzed for trends and relationships between them. While the fermentations with higher initial assimilable nitrogen concentrations had higher maximum fermentation rates, this did not guarantee successful fermentation outcomes in the tailing stage of the fermentation. Neither the initial, final, minimum and maximum temperatures, nor the initial pH, titratable acidity, measured yeast-assimilable nitrogen and primary amino nitrogen concentrations had any significant correlation with the maximum fermentation rate or successful completion of the fermentation. These results suggest that the initial juice-assimilable nitrogen measurements for these juices are of limited use in predicting slower and incomplete fermentation outcomes.

Effect of intracanal cryotherapy on post-operative pain in single-visit endodontic retreatment: a randomized clinical trial

BackgroundThis randomized clinical trial aimed to evaluate the effect of intracanal cryotherapy with 2–4 °C normal saline irrigation on post-operative pain after single-visit non-surgical root canal retreatment.MethodsForty-six single-rooted, single-canal teeth requiring non-surgical root canal retreatment were randomly assigned to two groups (n = 23): a cryotherapy group and a control group. All the treatments were completed during a single visit. A combination of nickel-titanium and stainless-steel files was used for the removal of gutta-percha and root canal preparation, and irrigation was performed using 5.25% NaOCl and 17% EDTA. The cryotherapy group had a final irrigation temperature of 2–4 °C for 5 min before root canal obturation, whereas the control group received irrigation at room temperature. Post-operative pain levels were assessed via the Numerical Rating Scale at 6, 18, 24, 48, 72, and 168 h (up to 7 days). The number of analgesics consumed at the same intervals was also recorded. Statistical analysis was performed using the Chi-Square test, Mann-Whitney test, and Independent Samples test, with the significance level set at 0.05.ResultsThere was a statistically significant difference in post-operative pain between the cryotherapy group and the control group at 6 h after treatment (P < 0.05). However, post-operative pain levels were not significantly different at 18, 24, 48, 72, or 168 h after treatment (P > 0.05). Additionally, there was no statistically significant difference between the groups in terms of analgesic intake (P > 0.05).ConclusionIntracanal cryotherapy can effectively reduce short-term post-operative pain, but it has no effect on long-term pain or the need for analgesics.

Mechanical Response and Failure Analysis of Stainless-Steel Beams Exposed to Elevated Temperatures

This research investigates the structural behaviour of stainless-steel beams (SSBs) when subjected to extreme temperatures, specifically in the context of fire-induced deformations. High temperatures, typical of fire occurrences, exert large thermal loads on SSBs, leading in material property changes that make the metal more brittle, stiffer, and brittle. The objective of this study is to investigate extensively the behaviour of SSBs under the combined impact of heat transfer and applied loads, with a focus on substantial deflections. To completely assess the performance of SSBs, we undertake parametric investigations and systematic research efforts. The initial phase comprises a thorough review of relevant data about the behaviour of SSBs at increased temperatures. Afterwards, a parametric study of the web section is conducted to determine the performance of the SSBs under exposure to fire and applied stresses. In order to ease the numerical research, the finite element (FE) program ABAQUS CAE is used to simulate stainless steel I-section beams of varying diameters subjected to realistic fire conditions according to the ISO 834 standard fire curve. The average discrepancy between numerical forecasts and experimental data for six separate models about the final temperature readings is 2.74 percent. Prior to actual collapse, the axial displacement of the SSBs decreases by around 7.5%, showing significant temperature influences on their strength. In addition, the axial deformation of the SSBs exhibits greater displacements in the web portion than in the flange section following fire exposure and loading. This discovery highlights the need to take into account the unique thermal expansion and stiffness characteristics of the web and flange components during fire occurrences. Utilising the finite element approach in ABAQUS reveals the resistance of SSBs to increased temperatures. The findings highlight the potential advantages of using stronger SSBs to maximise the structural response under fire conditions. This study gives useful insights into the thermal behaviour of SSBs and has important implications for building fire-resistant structures, boosting the fire safety of constructions, and enhancing their resistance against fire risks.

Synthesis and Evaluation of an Innovative Biochar Nanocomposite Adsorbent Derived from Cycas Revoluta Seeds, with Potential Applications in the Removal of Cationic Dyes

In this study, novel and functional adsorbents were synthesized by using Cycas revoluta seed (CS) biomass. The biomass was subjected to a slow pyrolysis process at a final temperature of 500°C with a heating rate of 10°C/min to synthesize Cycas revoluta seed biochar (CSB). After the thermochemical conversion of biomass into biochar, the nanocomposite structure (ZrO2NP@CSB) was synthesized by adding 5% zirconium oxide (ZrO2) nanoparticles into biochar to increase the adsorption capacity. The synthesized adsorbents (CS, CSB, and ZrO2NP@CSB) were characterized by XRD, FTIR, SEM, and EDX. The adsorption efficiency of these three adsorbents was investigated to remove Malachite Green (MG) and Methylene Blue (MB) dye from an aqueous solution. According to the results obtained from the adsorption experiments of the nanocomposite structure, solution pH had a significant effect on the process and the highest adsorption efficiencies were achieved at pH 9. The optimum adsorbent dose was 0.5 g/L. The process reached an equilibrium after 45 minutes and 90 minutes for MG and MB, respectively. The relevant data were in good agreement with the pseudo-second-order kinetic model. The maximum adsorbent capacities were 129.87 and 117.93 mg/g for MG and MB, respectively. The adsorption mechanism follows a monolayer Langmuir isotherm model. Experiments were carried out at different temperatures (25, 35, 45°C) to determine the effect of temperature on adsorption, and dye removal efficiency slightly increased with temperature. When repeated batch adsorption experiments were compared for raw biomass, biochar, and biochar nanocomposite adsorbents, it was observed that the raw adsorbent had a lower adsorption capacity than the biochar adsorbent. It was found that the biochar nanocomposite had the highest adsorption capacity among these three adsorbents. The findings suggest that ZrO2NP@CSB composite is a promising, cost-effective, and functional material for water treatment and can be employed as an alternative adsorbent for removing dyes.

Metabolic rearrangement enables adaptation of microbial growth rate to temperature shifts.

Temperature is a key determinant of microbial behaviour and survival in the environment and within hosts. At intermediate temperatures, growth rate varies according to the Arrhenius law of thermodynamics, which describes the effect of temperature on the rate of a chemical reaction. However, the mechanistic basis for this behaviour remains unclear. Here we use single-cell microscopy to show that Escherichia coli exhibits a gradual response to temperature upshifts with a timescale of ~1.5 doublings at the higher temperature. The response was largely independent of initial or final temperature and nutrient source. Proteomic and genomic approaches demonstrated that adaptation to temperature is independent of transcriptional, translational or membrane fluidity changes. Instead, an autocatalytic enzyme network model incorporating temperature-sensitive Michaelis-Menten kinetics recapitulates all temperature-shift dynamics through metabolome rearrangement, resulting in a transient temperature memory. The model successfully predicts alterations in the temperature response across nutrient conditions, diverse E. coli strains from hosts with different body temperatures, soil-dwelling Bacillus subtilis and fission yeast. In sum, our model provides a mechanistic framework for Arrhenius-dependent growth.

Study of aerodynamic parameters of air distributors during interaction of round non-coaxial jets

Purpose of reseach. The aim of the work is to determine the parameters of the resulting flow in the interaction of counter-misaligned air flows to ensure an intensive decrease in air velocity in production and technological premises of small volume. To achieve this goal, it is necessary to solve such tasks as analyzing existing theoretical provisions and methods for calculating air distribution systems for small production and technological premises; development of a mathematical model of the process of interaction of oncoming incompatible flows and to determine the parameters of the resulting air flow depending on the geometric characteristics of the device. The object of the study is the supply ventilation systems in industrial and technological premises of small volume with insignificant thermal loads. The subject of the study is the processes of formation of the resulting air flow created by the interaction of countermisaligned air flows.Methods. Methods of mathematical modeling of air flow motion based on the equations of aerodynamics.Results. The aerodynamic characteristics of the resulting jet are obtained – the Boussinesq coefficient and the velocity field coefficient.Conclusion. In the ambiguities, between two-meter-long-range extravehicular jets and two-meter-long-range converging streams in the inner regions, a spatial vortex zone is formed with a maximum extravehicular gradient velocity. At the boundary of the jet stream there is an intense interaction with the surrounding air, the vector of the propeller is directed by the opposite direction, and the quantity of the speed of the plane depends on the speed of the jet, which changes the nature of the swirling movements. The results show that the actual level of overshoot during a load surge is determined in the first approximation by the increment value multiplied by the difference in the values of thermal conductivity, winding-oil at the initial and final temperatures of the oils in the channels of the cooled windings, and this difference itself depends on the magnitude of the incremental damage. Optimal factor intervals for the values of the maximum value of the functions are obtained: t – from 40 to 120; ρ – from 800 to 900; c – from 1.4 to 2.3.

SYNTHESIS AND RESEARCH OF THE CATALYTIC SYSTEM xAlPO4 . yCu3(PO4)2

Individual orthophosphate catalysts AlPO4 and Cu3(PO4)2 were synthesized. A new synthesis technique was developed and a new complex aluminum-copper (II) orthophosphate catalytic system of the type xAlPO4·yCu3(PO4)2 was obtained based on them (К-1–К-7), which has the predicted physical and chemical properties. The content of both orthophosphates in the catalyst structure varies in the range of 0.5 - 99.5 wt. %. At the final heat treatment temperature (700oC), all synthesized complex catalysts K-1–K-7 are X-ray crystalline. The process of thermal treatment of catalysts contributes to their gradual dehydration and release of water from the structure of the samples, as well as the occurrence of characteristic endothermic effects at the appropriate temperatures. At high temperatures of heat treatment (about 500 oC), the processes of crystallization of the structures are observed on the synthesized samples K-1–K-7. Heating of all samples of a complex catalytic orthophosphate system of the type xAlPO4.yCu3(PO4)2 at temperatures above 700 oC leads to their complete dehydration and the formation of anhydrous salts. It can be predicted that the synthesized new complex oxide catalytic heterogeneous systems of the type xAlPO4.yCu3(PO4)2 have been will show improved both acidic surface properties and catalytic parameters: activity and selectivity in reactions of partial oxidation of n-alkanes to valuable products.

Molecular dynamic simulations of adiabatic self-reaction in Al@Ni core-shell nanoparticles

Abstract Al@Ni core-shell nanoparticles are attracting significant attentions for using as a promising material. In this paper, the self-reaction thermochemical behavior of Al@Ni nanoparticles was studied by molecular-dynamics (MD) simulations to characterize the final reaction temperature and self-heating rate. The analysis was carried out in canonical-constant temperature (NVT) and microcanonical-constant energy (NVE) ensembles using an embedded atom method. The ignition temperature was in the range of 700 K ∼ 1300 K, the core-shell thickness ratio of 1:1 ∼ 7:1 and the nanoparticle radius of 2 nm ∼ 8 nm were considered. When the ignition temperature was 1100 K, the nanoparticle radius was 8 nm, the core-shell thickness ratio was 3:1, the final reaction temperature was highest of 1955 K. As the ignition temperature was 1100 K, the nanoparticle radius was 4 nm, the core-shell thickness ratio was 3:1, the self-heating rate was highest of 3.04×1012K/s. These results obtained from the MD simulations of Al@Ni nanoparticles are helpful to understand the energy release mechanism.

Условия для самовоспламенения при смешении продуктов горения с топливно-воздушной смесью

To date, the possibility of self-ignition of systems obtained due to mixing a cold air-fuel mixture with hot combustion products has been established. The topic of potential generation of such mixtures, however, is understudied. The article attempts to determine the conditions under which self-igniting systems are generated in the case considered. For the studies, a model of an ideal mixing reactor with increasing mass and temperature in the system under condition of constant pressure and mass flow of combustion products inflowing to the system has been applied. The cold air-fuel mixture is initially contained in the system. The mass flow and final mixing temperature are preset. The preset mixing temperature is determined without considering chemical reactions whereas the induction period considers the chemical reactions during mixing. Flaming must not be initiated in the system, otherwise mixing does not occur. This condition complies with the high-intensity turbulence requirement for an energetic cold air-fuel mixture. Less strict requirements are applied to the mixing of highly diluted or non-combustible air-fuel mixtures. The study has adopted the requirement of either the Damkeller number, Da &lt; 1 or the Karlowitz number Ka &gt; 100. As a result of that, requirements for the intensity and scale of turbulence, the velocity and transverse size of the jet, and mixing combustion product are derived. On the other hand, the hot flow parameters are restricted by the condition to ensure the required flow so that the temperature in the system could reach the preset value during a specific period that cannot exceed the induction period by more than 10 times. The latter requirement is the consequence of the adopted scenario of ideal mixing with monotonously increasing temperature in the system. The global quenching condition is met for highly diluted mixtures and even for non-combustible mixtures. These conditions are represented in the plane «elocity — transverse size of the jet» as areas restricted with straight lines that meet the imposed requirements.

Pyrolysis kinetics and reaction mechanism of waste medical masks by sectional heating process

The COVID-19 epidemic has led to a significant upsurge in the accumulation of waste medical masks. This work focuses on the detailed examination of waste medical masks’ pyrolysis kinetic and reaction mechanism, employing a sectional heating process. The degradation properties were analyzed via thermal gravimetric analysis and pyrolysis reactor. The comprehensive kinetic process was studied using model-free and model-fitting methods, which determined the apparent activation energy and pre-exponential factor. The calculated average value for these parameters was 221.32 kJ/mol and 2.6 × 1014 min−1, respectively. The pyrolysis process was carried out at three distinct temperatures: 380, 470, and 490 ℃, corresponding to the initial peak degradation rate and final degradation temperatures determined by TGA results. The total yield of oil, gas and tar was 88.6 %, 11.3 % and 0.1 %, respectively. The identification and quantification of pyrolysis products were achieved through GC–MS and FTIR. It was observed that higher pyrolysis temperature facilitated the generation of alkanes and hydrocarbons with lower carbon chain lengths in oil products and propylene monomers in gas products. The dominant pyrolysis products in oil under 380 ℃, 470 ℃ and 490 ℃ were C20, C20 and C12 with the yield of 36.17 %, 48.96 % and 43.35 %, respectively. And the corresponding dominant products in gas all were propylene with the yield of 34.74 %, 53.02 % and 54.55 %, respectively. Furthermore, a reaction mechanism was postulated to elucidate the pyrolysis process under varying temperature conditions.

Influence of half open coil structures on overall continuous induction heating of variable cross section pipe before quenching

Resistance heating of variable cross-section pipes before quenching can cause austenite grain coarsening, leading to inferior properties in thin-wall segments. This method also suffers from low heating efficiency, high energy consumption, and is time-consuming. This study compared the effects of variable cross section (VCS) and equal cross section (ECS) coil structures on overall continuous induction heating, aiming to investigate rapid and uniform heating solutions for this type of pipe. The results showed that the workpiece could be heated to the quenching temperature of 890 °C within 30 min using both coils. The ECS coil demonstrated superior heating efficiency, while the VCS coil exhibited better heating quality along the axial direction. Optimizations in VCS coil, including dynamic power control and insulation measures significantly improved the heating quality, with the final temperature distribution of the workpiece basically meeting the quenching requirements. Furthermore, an induction heating experiment was conducted to validate the reliability of the analysis model, showing good alignment with the simulated results. Overall, the application of half-open coil induction heating for variable cross-section pipes is feasible, offering a high efficiency and qualified heating quality. However, this technology is better suited for large-scale manufacturing, as each coil structure can only match one product specification; otherwise, it could significantly increase equipment costs. Additionally, for heating large workpieces, the workshop should have sufficient electrical load capacity to meet the power supply requirements.