Experimental Temperature Research Articles

Diurnal temperature variation in surface soils: an underappreciated control on microbial processes

Large diurnal temperature changes (ΔT) (or the diurnal temperature range (DTR)) in surface soils, ranging from 5°C to often greater than 20°C, are generally acknowledged to occur yet largely disregarded in studies that seek to understand how temperature affects microbially-mediated carbon and nitrogen cycling processes. The soil DTR is globally significant at depths of 30 cm or less, occurring from spring through summer in temperate biomes, during summer periods in the arctic, and year-round in the tropics. Thus, although temperature has long been considered an important factor in controlling microbial processes, our understanding of its effects remains incomplete when considering natural soil temperature cycles. Here we show: (1) documented impacts of diurnal temperature changes on microbial respiration rates; (2) documented observations of surface soils with large DTR (>5°C) that affect soil microbial mineralization rates and redox potentials of important biogeochemical reactions; and (3) direct evidence that the constant temperature regime typically used in laboratory soil incubation studies may therefore lead to mischaracterization of in situ temperature controls on microbially influenced processes in the environment. The overall effect is that the DTR yields process rates that are often higher than what has been observed under experimental mean temperature incubation. We suggest that overlooked genetic mechanisms, such as the presence of a circadian clock or thermophilic activity during summer months, are likely contributing to the observed effects of the DTR. To improve our understanding of climate change effects on soil greenhouse gas emissions, nutrient cycling, and other biogeochemical soil processes, we propose a paradigm shift in approach to temperature-inclusive process modeling and laboratory incubation studies that accounts for the important role of natural diurnal temperature fluctuations.

Quasi-Classical Models of Nonlinear Relaxation Polarization and Conductivity in Electric, Optoelectric, and Fiber Optic Elements Based on Materials with Ionic–Molecular Chemical Bonds

A generalized scientific review with elements of additions and clarifications has been carried out on the methods of theoretical research on the electrophysical properties of crystals with ionic–molecular chemical bonds (CIMBs). The main theoretical tools adopted are the methods of quasi-classical kinetic theory as applied to ionic subsystems relaxing in layered dielectrics (natural silicates, crystal hydrates, various types of ceramics, and perovskites) in an electric field. A universal (applicable for any CIMBs class crystals) nonlinear quasi-classical kinetic equation of theoretical and practical importance has been constructed. This equation describes, in complex with the Poisson equation, the mechanism of ion-relaxation polarization and conductivity in a wide range of polarizing field parameters (0.1–1000 MV/m) and temperatures (1–1550 K). The physical model is based on a system of non-interacting ions (due to the low concentration in the crystal) moving in a one-dimensional, spatially periodic crystalline potential field, perturbed by an external electric field. The energy spectrum of ions is assumed to be continuous. Elements of quantum mechanical theory in a quasi-classical model are used to mathematically describe the influence of tunnel transitions of hydrogen ions (protons) during the interaction of proton and anion subsystems in hydrogen-bonded crystals (HBC) on the polarization of the dielectric in the region of nitrogen (50–100 K) and helium (1–10 K) temperatures. The mathematical model is based on the solution of a system of nonlinear Fokker-Planck and Poisson equations, solved by perturbation theory methods (via expanding solutions into infinite power series in a small dimensionless parameter). Theoretical frequency and temperature spectra of the dielectric loss tangent were constructed and analyzed, the molecular parameters of relaxers were calculated, and the physical nature of the maxima of the experimental temperature spectra of dielectric losses for a number of HBC crystals was discovered. The low-temperature maximum, which is caused by the quantum tunneling of protons and is absent in the experimental spectra, was theoretically calculated and investigated. The most effective areas of scientific and technical application of the theoretical results obtained were identified. The application of the equations and recurrent formulas of the constructed model to the study of nonlinear optical effects in elements of laser technologies and nonlinear radio wave effects in elements of microwave signal control systems is of the greatest interest.

Effects of Different Temperature and Humidity Regimes on Reproduction and Development of Lucilia sericata (Meigen,1826) Female Populations

Aim to study: The development of animals such as Lucilia sericata (Diptera: Calliphoridae) that cannot metabolically regulate body temperature and maintain body temperature by absorbing heat from the surrounding environment (i.e., poikilotherms) has been extensively described using the temperature collection model (Grassberger & Reiter, 2002). This study aimed to investigate oviposition tendency and oviposition development times and ideal temperature and humidity values for mass rearing of the green bottle fly Lucilia sericata, which was studied in the laboratory at three different constant temperatures (25°C, 30°C, 35°C) and three different constant humidities (35% R.H., 50% R.H., and 65% R.H.). Material and methods: The humidity was fixed at each experimental temperature to determine the maximum egg-laying and development time at different temperatures, and the number of days and degrees required to complete each stage was determined. The temperature was fixed in the different humidity experiments, and the insectarium was examined under controlled conditions in a 12:12 (L:D) photoperiod cycle. Results: A significant difference was obtained between the number of Lucilia sericata eggs laying at different temperature values (χ2=21.143, P < 0.05). A significant difference was found between the number of Lucilia sericata eggs laying at different humidity values (χ2=17.913, P < 0.05). However, there is no significant difference between the number of egg-laying larvae at 50% and 65% humidity values (P > 0.05). Conclusion: For the egg-laying tendency of Lucilia sericata flies in a specific insectarium under laboratory conditions, a temperature of 35°C and a humidity of 50% is ideal.

Finite Element Simulation and Experimental Analysis of the Thermo-Mechanical Properties of Dissimilar S275 and 316L Austenite Stainless Steels using the RFW Process

This research examines the effect of thermomechanical and microstructural constituents on welding of AISI 316L (austenite stainless steel) and S275 steel. A Finite Element Model (FEM) was constructed using ANSYS 19.1, and an experimental study was conducted using the Rotary Friction Welding (RFW) process. It was determined that there is a genuine correlation between the simulation FEM and the experimental procedure with regard to the thermal profile and ultimate yield strength, particularly when a welding speed of 2,000 rev/min is employed. At that speed, the higher temperature recorded and calculated was 1,450 oC. The discrepancy between the numerical FEM and the experimental temperature profile for the peak temperature calculation was determined to be 2.78%. The mechanical analysis was conducted through tensile force calculations and experiments, the results of which indicated an estimated error of 12%. The calculated error for the ultimate yield strength of the various samples is less than 6% for tensile strength. Upon tensile testing, failure occurred in the S275 sample. The microstructure exhibited increases in Cr and Ni of 1.2% and 1.01%, respectively, in comparison to the base metal of 316L stainless steel.

Fuel mobility dynamics and their influence on applied smouldering systems

Many recent environmentally beneficial applications of smouldering treat hazardous organic liquid fuels in inert porous media. In these applications, organic liquid mobilization can affect the treatment process, and the dynamics are poorly understood. Organic liquid mobilization is therefore a key knowledge gap that hinders the optimization of applied smouldering. This is especially the case in large scales where mobilization appears to be more significant. Liquid mobilization inside a porous medium cannot be easily measured directly, therefore numerical modelling is essential to understand the fundamental processes and to clarify the effects and dynamics of the fuel mobilization on the smouldering reaction. Contrasting numerical models with experimental temperature measurements have revealed many aspects of smouldering that cannot be measured. In this study, a previously developed 1D smouldering model was equipped with multiphase flow equations and compared against laboratory column experiments. The combination of model and experiments has served to quantify the dynamics of organic liquid fuel mobility by simulating high (i.e., non-mobile) and low (i.e., mobile) viscous fuels. The findings from this study shed light on the complicated interplay between multiphase flow, heat and mass transfer, and smoulder chemistry common to many applied smouldering systems. Numerical results confirmed that increasing the viscosity results in fuel remaining in the reaction zone and led to an increase in the peak temperature and smouldering front velocities. Lower viscosity fuels mobilized away from the reaction zone, thereby accumulating fuel in the pre-heating zone of the reactor. The fundamental understanding generated from this research will improve the design, implementation, and optimization of smouldering-based technologies for environmentally beneficial applications worldwide.

Experimental and numerical investigations of cavity flame spread in double skin façade

In recent decades, double-skin façades (DSFs) have gained popularity in modern commercial buildings. However, their cavities can potentially accelerate flame spread, raising significant concerns regarding façade fire safety. Given that existing studies focus on the DSF component failures and fire stop measures without modeling validation, this study presents real-scale DSF fire experiments and modeling in accordance with JIS A 1310, conducted without combustibles to clarify fire behaviors within the cavity. The experiments employ HRRs of 600-900 kW and cavity depths of 0.4 and 0.8 m, highlighting that flame attachment to the facing wall is dependent on HRRs rather than cavity depths. Subsequently, Computational Fluid Dynamics (CFD) is utilized to investigate DSF fires, with validation against experimental temperature distribution and flame morphology. Furthermore, the validated CFD modeling is applied to scenarios with extended cavity depths and varied opening shapes, indicating that a cavity depth of ≥0.7 m mitigates flame spread for an opening ratio of n≥1. The Modified-McCaffrey-Yokoi (MMY) model is proposed to characterize façade flame temperatures across varied cavity depths, and its convergence, featured by opening shapes and HRRs, is categorized to distinguish cavity flame behavior.

Study on the change of the oil-paper insulation’s AC conductivity characteristics based on dielectric response in frequency domain

Oil-immersed power equipment (transformers and high voltage bushings) are key components of power systems. Oil-paper insulation has endured complex and harsh operating conditions when used as a primary insulation system, so it is essential to determine the insulation state of oil-paper insulation system to ensure a stable operation for the power grid. The oil-paper insulation’s conductivity behavior can effectively characterize the degree of insulation deterioration. However, the relationship between the alternating current (AC) and direct current (DC) conductivity behavior for oil-paper insulation systems is still unclear in current research, resulting in limitations in the traditional evaluation model’s application. Therefore, this paper uses oil-paper insulation materials under different aging to carry out relevant research about the changing features of the complex AC conductivity under different test temperature environments. The influence of oil-paper insulation aging, test temperature, and excitation frequency on the complex AC conductivity is verified. Considering the correlation between low-frequency AC conductivity and DC conductivity, the frequency range of AC conductivity is extended by means of frequency temperature and conductance double translation. The temperature dependence of the AC conductivity behavior is defined over a wide frequency test range. The relaxation polarization process dominated the AC conductivity variation law is obtained. The impact of experimental temperature and insulation aging on the cumulative characteristic parameters of AC ionic mobility is clarified. This study theoretically corrects the traditional calculation model for AC conductivity of oil-paper insulation. The bias in conductivity calculations caused by only considering a single relaxation polarization process is eliminated. The conductivity model that can characterize multiple relaxation polarization processes in the dielectric is established. This model provides theoretical support for the later assessment of oil-paper insulation state depending on conductance behavior.

Development of an atmospheric boundary layer detection system based on a rotary-wing unmanned aerial vehicle.

To enhance meteorological detection methods, an atmospheric boundary layer detection system based on a rotary-wing unmanned aerial vehicle (UAV) was proposed. Computational fluid dynamics (CFD) was employed to model the surrounding airflow distribution during UAV hovering, thereby determining the optimal positions for sensor installation. A novel radiation shield was designed for the temperature sensor, offering both excellent radiation shielding and superior ventilation. To further improve temperature measurement accuracy, an error correction model based on CFD and neural network algorithms was designed. CFD was used to quantify the temperature measurement errors of the sensor under different environmental conditions. Subsequently, random forest and multilayer perceptron algorithms were employed to train and learn from the simulated temperature errors, resulting in the development of the error correction model. To validate the accuracy of the detection system, comparative experiments were conducted using the measurement values from the 076B temperature observation instrument as a reference. The experimental results indicate that the mean absolute error, root mean square error, and correlation coefficient between the experimental temperature errors and the algorithm-predicted errors are 0.055, 0.066, and 0.971 °C, respectively. The average error of the corrected temperature data is 0.05 °C, which shows substantial agreement with the reference temperature data. During UAV hovering, the average discrepancies between the temperature, humidity, and air pressure data of the detection system and the ground-based reference data are 0.6 °C, 1.6% RH, and 0.77 hPa, respectively.

State of health estimation of lithium-ion battery cell based on optical thermometry with physics-informed machine learning

Effective thermal management and accurate state of health (SOH) estimation of lithium-ion batteries is crucial for ensuring their safety, reliability, and longevity. This study presents three innovative physics-informed machine learning-based SOH estimation techniques trained and demonstrated using experimental temperature data. Temperature distribution measurements were obtained using optical frequency domain reflectometry with optical fibers embedded in a cylindrical lithium-ion battery cell under various SOH. One of the trained model accurately predicted the SOH of a cell within 2% with only a 10-minute measurement. This technique also enables the estimation of SOH for individual cells connected in series or parallel within a battery module or pack simultaneously, thereby reducing the overall SOH estimation uncertainty without the need for disassembly. Furthermore, this not only highlights the necessity of precise thermal management in maintaining battery health but also offers a practical and efficient solution for real-time SOH monitoring in battery systems.

Rapid osmocontractile response of motor cells of Mimosa pudica pulvini induced by short light signals.

The Mimosa pudica leaf has motor organs allowing movements driven by cell osmotic changes in the parenchyma cells in response to various stimuli. Short white light pulses induce rapid and large seismonastic-like movements (denoted "photostimulation") of the primary pulvini in various leaves within 120 s after the onset of light. An early event recorded is a wavelength-related modification of the plasma membrane difference: potential depolarization under white, blue, green, and red wavelengths, and hyperpolarization under far red wavelengths (and also in darkness). The photoreactivity of the pulvini is controlled by a circadian rhythm and modulated by the applied diurnal photoperiod cycle (photophase ranging from 6 to 18 h). The reactivity varied among plants and even between leaves on the same plant. The level of reactivity is related to the photon fluence rate in the range from 10 to 140 μmol m-2 s-1 under white light and to the experimental temperature in the range 15°C-35°C. An "accommodation" to light supply is evidenced by a modulation of the reactivity in relation to the schedule of light application under low fluence rates and the introduction of short darkness intervals during the first 30-s light pulse. The blue light-induced photostimulation is under phytochrome control.

Assessing the severity of thermal discomfort in a building in the course of hot and humid climate.

This work is an application of experimental temperature data previously collected in a residential building in Douala, Cameroon, in order to analyze thermal discomfort. The data was collected according to three occupancy scenarios over 12 month period using thermohygrometer sensors. The temperature data are analysed in comparison with the comfortable temperature range from 24°C to 28°C. The degree hour (DH) method was used to assess the severity of thermal discomfort in a hot and humid climate. The results reveal that the open C1, closed C2 and inhabited C3 rooms corresponding to scenarios C1, C2 and C3 respectively, have 7270.6°H, 9063.9°H and 10023°H. The inhabited room C3 has the largest DH and although the room C1 has the smallest DH, the latter largely exceeded the tolerable limit value of 1250°H set by the RE2020 Environmental Regulations. Results from this work can serve in building modelling for researchers and architects to act for the alleviation of thermal discomfort in regions with hot and humid climate.

Fabrication of Flexible SWCNTs/Polyurethane Coatings for Efficient Electric and Thermal Management of Space Optical Remote Sensors

Given the requirement of high-efficiency thermal dissipation for large-aperture space optical remote sensors, a radiator based on single-walled carbon nanotubes (SWCNTs) filled with waterborne polyurethane (SWCNTs/WPU) coatings was proposed in this work. In situ polymerized SWCNTs/WPU coatings allowed for the uniform distribution of acid-purified SWCNTs in WPU matrix. Modified oxygen-containing groups on purified SWCNTs enhanced the interfacial compatibility of SWCNTs/WPU and enabled an improved tensile strength 9 (26.3 MPa) compared to raw-SWCNTs/WPU. A high electrical conductivity of 5.16 W/mK and thermal conductivity of 10.9 S/cm were achieved by adding 49.1 wt.% of SWCNTs. Only 2.85% and 4.2% of declined ratios for electric and thermal conductivities were presented after 1000 bending cycles, demonstrating excellent durability and flexibility. The designed radiator was composed of a heat pipe, SWCNTs/WPU coatings and an aluminum honeycomb core, allowing for −1.6~0.3 °C of temperature difference for the in-orbit temperature and thermal balance experimental temperature of the collector pipe. Moreover, the close temperature difference for the in-orbit and ground temperatures of the radiator indicated that the designed radiator with high heat dissipation met the mechanical environment requirements of a rocket launch. SWCNTs/WPU would be promising electric/thermal interface materials in the application of space optical remote sensors.

Fitted Fv/Fm temperature response curves: applying lessons from plant ecophysiology to acute thermal stress experiments in coral holobionts

Abstract Maximum photochemical efficiency, F v /F m , is the preferred metric for quantifying the loss of photosystem II (PSII) function in photosynthetic algal symbionts (Symbiodiniaceae) of reef-building corals exposed to heat stress, particularly at the early stages of coral bleaching. Loss of PSII function can be quantified as the temperature at which a holobiont loses 50% of maximum photochemical efficiency (50% effective dose, or ED50) when exposed to a range of experimental temperatures. Here, we demonstrate that dose–response curves can be substantially more informative about a coral’s stress response by including ED5 (5% effective dose), ED95 (95% effective dose), and decline width (ED95–ED5) values in summary statistics. These parameters are commonly used in plant ecophysiology and can be extracted from fitted F v /F m temperature response curves. This suite of metrics provides a broader understanding of the loss of PSII function in acute thermal stress experiments in corals and could enhance comparability among coral and plant studies.

Homogeneous Crystal Nucleation in Poly (butylene succinate-ran-butylene adipate): Challenging the Nuclei-Transfer Step in Tammann's Method.

The kinetics of homogeneous crystal nucleation and the stability of nuclei were analyzed for a random butylene succinate/butylene adipate copolymer (PBSA), employing Tammann's two-stage crystal nuclei development method, with a systematic variation of the condition of nuclei transfer from the nucleation to the growth stage. Nuclei formation is fastest at around 0 °C, which is about 50 K higher than the glass transition temperature and begins after only a few seconds. Due to the high nuclei number, spherulitic growth of lamellae is suppressed. In contrast, numerous μm-sized birefringent objects are detected after melt-crystallization at high supercooling, which, at the nanometer-scale, appear composed of short lamellae with a thickness of a few nanometers only. Regarding the stability of nuclei generated at -30 °C for 100 s, it was found that the largest nuclei of the size-distribution survive temperature jumps of close to 80 K above their formation temperature. The critical transfer-heating rate to suppress the reorganization of isothermally formed nuclei as well as the formation of additional nuclei during heating increases with the growth temperature at temperatures lower than the maximum of the crystallization rate. This observation highlights the importance of careful selection of the transfer-heating rate and nuclei development temperature in Tammann's experiment for evaluation of the nucleation kinetics.

Boosted photoinduced charge separation in FeNi2S4@Cd0.9Zn0.1S Step-scheme heterojunction for photothermal assisted photocatalytic water splitting into hydrogen

Rational design of photocatalysts with photothermal effect to maximize light utilization is pivotal in achieving superior photocatalytic efficiency. In this work, by coating Cd0.9Zn0.1S (CZS) nanorods on hollow FeNi2S4 (FNS) microspheres with photothermal effect, a novel FeNi2S4@Cd0.9Zn0.1S (FNS@CZS) Step-scheme (S-scheme) heterojunction photocatalyst was constructed for efficient photothermal-assisted hydrogen (H2) evolution via simultaneously employing light and thermal energy. The hollow structure of FNS microsphere not only provides abundant reactive sites but also serves as a supportive substrate for CZS nanorods, effectively inhibiting their agglomeration. And the unique hollow structure of FNS allows for multiple reflections and refractions of visible light, enhancing the local temperature of the photocatalyst. This effectively minimizes thermal losses within the composite system, thereby enhancing the efficiency of light energy utilization. Furthermore, the formation of the S-scheme heterojunction facilitates the efficient separation of photogenerated charge carriers and enhances the activity of redox reactions, thereby boosting the overall photocatalytic activity. Experimental results reveal that the H2 production rate of the FNS@CZS heterojunction reaches 12.9 mmol·g−1·h−1, which is 25.1 times higher than that of pristine CZS. By controlling the experimental temperature, the impact of the photothermal effect on the photocatalytic H2 production rate has been clarified. According to relevant evidence from infrared thermography and DFT calculations, comprehensive analyses and discussions were conducted on the photothermal effect and S-scheme charge transfer mechanisms. This study offers guidance on designing photothermal-enhanced photocatalysts to achieve satisfactory H2 production activity.

Research on the psychology, physiology and cognitive ability of the work efficiency of special vehicle members

The combat effectiveness of special vehicles is related to the comprehensive national strength of the country. In addition to the performance of the vehicle itself, the combat capability of the crew is also crucial, and the work efficiency will affect the combat capability of the crew.This paper summarizes the effects of thermal and noise environments on crew efficiency and the evaluation methods of work efficiency using special vehicles as experimental platforms. A total of 12 environmental conditions were designed, the experimental temperature covers 25 °C, 29 °C, 33 °C, 37 °C, noise covers 50 dB, 70 dB, 85 dB. The effects of temperature and noise on the physiological, psychological and cognitive abilities of the occupants were quantitatively analyzed through human ergonomics simulation experiments. The results show that the noise has a significant effect on the occupant's work efficiency in a low-temperature environment, while the temperature becomes the dominant influence factor in a high-temperature environment. When operating temperatures reached 29 °C, occupant combat performance was optimal, whereas at 33 °C and above, the efficiency decreased significantly. This research provides a theoretical basis for optimizing the environment of special vehicle cabins, and offers a scientific temperature control scheme to improve the crew's efficiency.

Direct and indirect assessment of the elastocaloric properties of cast NiMnTi alloys

The study of the elastocaloric effect of NiMnTi alloys is a key topic for developing materials for sustainable and efficient solid-state cooling and heating applications. In the current work, the mechanical behavior of two arc melted and heat treated NiMnTi alloys with 15 and 18 at% of Ti has been investigated. The effects of heat treatments and operating conditions on the mechanical and caloric properties of the alloys have been assessed through calorimetric analysis, isothermal stress-strain compressive measurements, and adiabatic tests. To evaluate the caloric performance of the NiMnTi alloys, both experimental and theoretical adiabatic temperature changes have been identified, and the isothermal entropy change involved in the stress-induced martensitic transformation has been computed from the discrete integration of the stress-strain curves. The NiMnTi alloys treated at 900 °C exhibited better caloric performance than those treated at 1000°C. Specifically, the sample that achieved the highest experimental positive and negative ΔT values (10.2 °C and −12.6 °C, respectively) was the NiMnTi alloy with 15 at% of Ti and heat treated at 900 °C. This study provides a detailed analysis of the physical properties, functionality, and caloric properties of polycrystalline NiMnTi fabricated through a melting process, considering its potential use in solid-state cooling and heat pumping technologies.

Study on microcosmic properties and temperature simulation of foamed polypropylene composites

The injection molding procedure and the compression molding procedure of foamed polypropylene composite are studied. The pore diameter, pore density, and microscopic topography for polypropylene composites was studied by experiments of slicing samples. The foamed temperature is very important for foamed property of the foamed polypropylene composite materials. To analyze the effect of temperature distribution, the virtual boundary meshfree Galerkin method (VBMGM) was employed the radial basis function interpolation method to obtain a detailed discretization formula. The temperature of experiment and numerical calculation from zone a to zone d in different zones of the injection molding procedure is reduced from 406.35 K to 311.63 K; the temperature from Ma zone to Md zone in the compression molding procedure is reduced from 326.35 K to 309.14 K. The experimental observation of the injection molding procedure shows that the foamed property in zone c is ideal, and the average pore diameter and pore density are 26.5 µm and 2.43×109 cells·cm−3 respectively. According to the experimental observation of compression molding process, the foamed property in Md zone is ideal, and the average pore diameter and pore density are 131.2 µm and 6.3×104 cells·cm−3. These results are of great significance to the foam molding of polypropylene composites.

SIMULATION OF PREHEATING AND HEATING WHEN CONNECTING POLYETHYLENE PIPES WITH ELECTROFUSION COUPLINGS

Existing machines for electrofusion welding of polyethylene pipes provide a high-quality connection at air temperatures no lower than minus 10 °C. However, if welding is required at lower temperatures, a layer of heat-insulating material is used to reduce the cooling rate. This insulation is selected based on the air temperature and the size of the welded pipes. This paper investigates the dynamics of temperature fields at the stages of heating, temperature equalization and heating using a new technology of welding at low temperatures. The proposed technology eliminates the use of thermal insulation material and allows welding to be carried out automatically.The paper presents a mathematical model that describes the thermal process when performing all welding operations at low temperatures. The model describes the thermal process with and without phase transformation. The well-known method of end-to-end calculation with the introduction of effective heat capacity is used to consider the heat of phase transition in the temperature range. The model also considers the dependence of the thermophysical properties of polyethylene on the degree of crystallinity.The following text presents the results of preheating and temperature equalization calculations for welding polyethylene pipes of the PE 100 SDR 11 brand with a diameter of 160 mm at an air temperature of minus 40 °C. To accurately describe the thermal process of real welding, experimental temperature data was used for parametric identification. It is shown that as a result of preheating and temperature equalization in the weld and thermally affected zones and outside them at a distance of more than 10 mm, the temperature values do not exceed acceptable limits. The resulting temperature distribution allows heating according to the standard welding mode. Calculations show that when the heating is completed, the volume of the polyethylene melt corresponds to the volume of the welding melt at the allowed air temperature.These findings can be used to develop a technique for controlling the movement of the crystallization front during welding at low temperatures.

Unveiling the Novel Mechanistic Insights and Role of Base in Zn‐Catalyzed Csp–Csp2 Cross‐Coupling Reaction

ABSTRACTA detailed mechanistic investigation of the Zn (II)‐catalyzed Csp–Csp2 (Sonogashira‐type) cross‐coupling reaction is reported herein, using the Density Functional Theory method. The present study unveiled an unconventional non‐redox mechanism for Zn‐catalyzed cross‐coupling reaction, where the oxidation state of Zn remains intact throughout the catalytic cycle. Our study further revealed the significant role of the base in controlling the feasibility of cross‐coupling reactions that are catalyzed by electron‐deficient metal centers. Our study indicates that K3PO4 acts as an ancillary ligand (Lewis base) for the electron‐deficient Zn (II) catalytic center rather than as a proton abstractor for the nucleophilic coupling partner (phenylacetylene) in this reaction. The active catalyst was identified to be a four‐coordinate bis‐DMEDA Zn (II) complex. The mechanism proceeds via the initial activation of the nucleophilic coupling partner (phenylacetylene), followed by the electrophilic coupling partner (organic halide) activation liberating the cross‐coupled product by a concerted nucleophilic substitution pathway. The turn‐over limiting step was identified to be the activation of the electrophilic coupling partner. The activation barrier obtained for the reaction, 31.0 kcal/mol concords well with experimental temperature requirements (125°C). The coordination by base is found to stabilize the rate‐determining intermediates and transition states involved in the reaction. The mechanistic insights gained from this study could aid in the rational design and development of sustainable cross‐coupling reactions using zinc as the catalyst.