Search Results (21)

Joining high-strength, cold-drawn Cu-Mg alloy conductors is a critical challenge for ensuring the reliability of high-speed railway catenary systems. This study investigates the evolution of mechanical properties and microstructure in Cu-0.43 wt% Mg alloy wires joined by multi-pass butt-upset cold welding without special surface preparation. High-integrity joints were achieved, exhibiting a peak tensile strength of 624 MPa (~96% of the base material’s strength). After four upsetting processes, the tensile strength of the weld can reach 90% of the original strength, and the gains from subsequent upsetting processes are negligible. Microstructural analysis revealed the joining process is governed by localized severe shear deformation, which forges a distinct gradient microstructure. This includes a transition zone of fine, equiaxed-like grains formed by dynamic recrystallization/recovery, and a central zone featuring a nano-laminar structure, high dislocation density, and deformation twins. A multi-stage dynamic bonding mechanism is proposed. It progresses from initial contact via thin film theory to bond consolidation through a “mechanical self-cleaning” process, where extensive radial plastic flow effectively expels surface contaminants. This work clarifies the fundamental bonding principles for pre-strained, high-strength alloys under multi-pass cold welding, providing a scientific basis to optimize this heat-free joining technology for industrial applications. Full article

Atrium spaces are widely applied in university buildings. However, achieving effective energy reduction while maintaining adequate daylighting and indoor comfort remains a major challenge at the early design stage. This study identifies key building form design variables significantly influencing atrium daylighting, energy use, and thermal comfort, including building orientation, atrium width-to-depth ratio, atrium aspect ratio, atrium bottom area ratio, and skylight–roof ratio. A multi-objective optimization (MOO) framework is proposed to balance daylight performance, energy consumption, and thermal comfort under fixed envelope parameters. Using typical single- and double-atrium teaching buildings in cold regions as case studies, this research adopts Useful Daylight Illuminance (UDI), Energy Use Intensity (EUI), and Discomfort Time Percentage (DTP) as key indicators to evaluate the interactions between design parameters and building performance. Based on the Pareto-optimal results for the studied prototypes, a south-by-west orientation, moderately slender atrium proportions, relatively compact atrium bottom areas, and medium skylight–roof ratios together yield a balanced performance. Compared with the reference to the initial solution, the optimized solutions reduce EUI by up to 5.66% while also improving UDI and DTP. These results are intended as quantitative references and optimization for early-stage geometric forms design of atrium teaching buildings in cold regions. Full article

This study addresses the multi-period, multi-item, single-stage capacitated lot sizing problem (CLSP) in a parallel machine environment with machine eligibility constraints under a make-to-order production policy. A mixed-integer linear programming (MILP) model is developed to minimize total operational costs, including production, overtime, extra shifts, inventory holding, and backorders. The make-to-order setting introduces additional complexity by requiring individualized customer orders, each with specific due dates and product combinations, to be scheduled under constrained capacity and setup requirements. The model’s performance is evaluated in the context of a real-world production planning problem faced by a manufacturer of cold-formed steel profiles. In this setting, parallel forming machines process galvanized sheets of cold-rolled steel into a variety of profiles. The MILP model is solved using open-source optimization tools, specifically the HiGHS solver. The results show that optimal solutions can be obtained within reasonable computational times. For more computationally demanding instances, a runtime limit of 300 s is shown to improve solution quality while maintaining efficiency. These findings confirm the viability and cost-effectiveness of free software for solving complex industrial scheduling problems. Moreover, experimental comparisons reveal that solution times and performance can be further improved by using commercial solvers such as CPLEX, highlighting the potential trade-off between cost and computational performance. Full article

At the critical stage of China’s economic transformation, promoting integrated development among the digital economy, economic resilience, and ecological protection becomes essential to achieve high-quality national development. This study takes 30 Chinese provinces (autonomous regions/municipalities) as research subjects. A comprehensive index system evaluates coupling coordination among the digital economy, economic resilience, and ecological protection. The three-system coupled coordination model and obstacle degree model are employed. The research investigates comprehensive evaluation levels of these three systems. Evolutionary characteristics of their coupled coordination are analyzed. Influencing factors are identified through systematic examination. Key findings reveal: (1) Provincial digital economy, economic resilience, and ecological protection generally maintained good comprehensive evaluation levels between 2011 and 2021. Significant regional development imbalances persist nationwide. (2) Coupled coordination among the three systems remains moderate but shows overall growth trends. Development characteristics demonstrate notable temporal inadequacies and spatial imbalances. Provinces achieving primary and intermediate coordination levels increased from 1 to 12 during the study period. (3) Spatial autocorrelation features prominently in the three-system coordination. Cold and hot spot areas exhibit clustered distribution patterns. (4) Main obstacles constraining three-system coupling coordination show temporal and regional variations. These evolving barriers collectively form a dynamic coupling system. Policy recommendations include: Advancing coordinated development and organic integration of the three systems; enhancing cross-regional collaboration to reduce spatial and systemic disparities; and implementing multi-source driving strategies to strengthen coordinated development momentum. Full article

The southern slope of the Tianshan Mountains features complex terrain and an arid climate, yet paradoxically experiences frequent extreme precipitation events (EPEs), which pose significant challenges for weather forecasting. This study investigates an EPE that occurred from 20 to 21 August 2019 using multi-source data to examine circulation patterns, mesoscale characteristics, moisture dynamics, and energy-instability mechanisms. The results reveal distinct spatiotemporal variability in precipitation, prompting a two-stage analytical framework: stage 1 (western plains), dominated by localized convective cells, and stage 2 (northeastern mountains), characterized by orographically enhanced precipitation clusters. The event was associated with a “two ridges and one trough” circulation pattern at 500 hPa and a dual-core structure of the South Asian high at 200 hPa. Dynamic forcing stemmed from cyclonic convergence, vertical wind shear, low-level convergence lines, water vapor (WV) transport, and jet-induced upper-level divergence. A stronger vorticity, divergence, and vertical velocity in stage 1 resulted in more intense precipitation. The thermodynamic analysis showed enhanced low-level cold advection in the plains before the event. Sounding data revealed increases in precipitable water and convective available potential energy (CAPE) in both stages. WV tracing showed vertical differences in moisture sources: at 3000 m, ~70% originated from Central Asia via the Caspian and Black Seas; at 5000 m, source and path differences emerged between stages. In stage 1, specific humidity along each vapor track was higher than in stage 2 during the EPE, with a 12 h pre-event enhancement. Both stages featured rapid convective cloud growth, with decreases in total black body temperature (TBB) associated with precipitation intensification. During stage 1, the EPE center aligned with a large TBB gradient at the edge of a cold cloud zone, where vigorous convection occurred. In contrast to typical northern events, which are linked to colder cloud tops and vigorous convection, the afternoon EPE in stage 2 formed near cloud edges with lesser negative TBB values. These findings advance the understanding of multi-scale extreme precipitation mechanisms in arid mountains, aiding improved forecasting in complex terrains. Full article

Cold forming offers high dimensional accuracy, energy and cost efficiency in the mass production of highly stressed components but is also associated with high tribological loads. Complex lubrication systems are required to ensure smooth production. As environmental standards rise, traditional zinc phosphate-based lubricants are to be replaced by less harmful single-layer systems. However, these new lubricants are temperature-sensitive, which requires precise knowledge of the temperatures in the forming zone for optimal design. Due to high compressive stress, conventional measuring methods cannot measure temperatures directly in the forming zone. In this work, lubricants are expanded into a temperature sensor using thermochromic pigments so that temperatures can be measured directly in the forming zone. This work outlines the selection and integration of the indicators, the development of a calibration method for thermochromic lubricants to characterize the correlation between colour value and temperature. It is shown that the lubricant behaviour does not deteriorate up to concentrations of 10%. The transfer of the measurement methodology from the laboratory application to the industrial multi-stage process has been successfully implemented and local temperature peaks are measured directly in the contact zone and correspond to the simulation results. The results of the work show an approach to closing the gap identified in existing research work, namely that the temperature cannot be measured directly in the forming zone during cold forging. The measuring system developed can be transferred to various processes in the future and contribute to the identification of correlations between temperature, lubricant failure and wear. Full article

This study evaluates the mechanical and electrical properties of copper-clad aluminum (CCA) wire prepared with a total cross-section reduction of 89% through a multistage cold drawing process and subjected to annealing at various temperatures. In addition to the CCA wire, individual samples of oxygen-free copper and aluminum, drawn with a cross-sectional reduction of 50%, were annealed under the same temperature conditions to enable a comparative analysis. Tensile tests for strength and elongation measurements were conducted, while electrical conductivity was assessed through resistivity tests. SEM and EDS analyses were performed to examine the diffusion thickness and the composition of intermetallic compounds generated at the Al/Cu interface of CCA wire. The tensile strength of the CCA wire decreased and its elongation increased up to 250 °C, after which were maintained. As the annealing temperature increased, intermetallic compound layers of Al₂Cu, AlCu, and Al₄Cu₉ were formed at the Al/Cu interface of the CCA wire, and their thickness increased. Electrical conductivity reaches a maximum at 200 °C and then continuously decreases, showing a negative linear correlation with an increase in the diffusion layer thickness of intermetallic compounds. The study confirmed that cold-drawn CCA wire achieves stable mechanical properties and maximum electrical conductivity at the optimal annealing temperature. Full article

Plant bacterial wilt is caused by Ralstonia solanacearum, a soilborne pathogen that infects plant conduits, leading to wilt disease. It is extremely difficult to cure plants infected with Ralstonia solanacearum; however, bactericide-loaded beads with hot-/wet-responsive properties may be able to release a biocide in line with the increase in the hot-/wet-associated activity of Ralstonia solanacearum, effectively killing the pathogenic cells and providing high levels of plant protection. A biopesticide, Tetramycin, was embedded in corn kernel powder (CKP)-based cores. An oil-phase mixture was sprayed onto the core surface to form a hot-/wet-responsive intermediate shell (IMS). Subsequently, a layer of ethyl cellulose (EC) and hydroxypropyl methyl cellulose (HPMC) was coated onto the IMS to create a single wet-responsive outer shell (OTS). The ratios of the components in the cores, including the corn kernel powder (CKP), xanthan gum (XG), and Tetramycin, were optimized, as well as those of the IMS, including pentaerythrityl tetrastearate (PETS), pentaerythrityl tetraoleate (PETO), polyethylene glycol stearate (PEG400MS), and polyethylene glycol monooleate (PEG400MO), and those of the outer shell (OTS), including ethyl cellulose (EC) and hydroxypropyl methyl cellulose (HPMC). A texture performance analysis, differential scanning calorimetry (DSC) analysis, thermogravimetric analysis (TGA), temperature and humidity response performance tests, scanning electron microscope (SEM) observations, and a field effectiveness test were conducted to characterize the Tetramycin-loaded beads. The results indicated that the optimal formula for the bead cores comprised a mass ratio of CKP/Tetramycin solution/XG = 13.5:23:2. The preferred mass ratio for IMS was PETS/PETO/PEG400MO = 10:30:10, and the formula for the applicable OTS consisted of a mass ratio of EC/HPMC = 5:1. In soil with a temperature of 30–35 °C and humidity of 30%, the release period of the Tetramycin-loaded beads, with a cumulative release rate of over 95%, could last up to 35 days. Furthermore, the Tetramycin-loaded beads exhibited a gradual and multi-cyclic release process under alternating hot/wet and dry/cold environments. The relative preventive efficacy of 54.74% on tobacco was revealed at a field-testing scale. A significant reduction in the abundance of Ralstonia solanacearum was also observed under treatment with the Tetramycin-loaded beads. The early fungal community structure exhibited higher consistency compared to the control. However, in the later stage, the diversity differences between the soil layers were restored. In conclusion, Tetramycin-loaded beads that could effectively respond to temperature and humidity fluctuations were developed, resulting in enhanced disease prevention efficacy and offering broad prospects for the prevention and control of Ralstonia solanacearum in agricultural settings. Full article

In order to solve the problems of performance degradation in energy tower heat pump (ETHP) systems under low temperature conditions and soil heat imbalances in ground source heat pump (GSHP) systems in cold regions, a new coupled system of ETHP and GSHP systems (the ET–GSHP system) and its operating mode were proposed. The mathematical model of the system was constructed along with the system’s form and operation scheme. The COP (coefficient of performance) and total energy consumption of the coupled system were then simulated and studied under a number of common operating situations. The heating season is divided into four periods based on varying outdoor ambient temperatures: the first period operates in series mode and has an average outdoor temperature of 2.38 °C; the second period operates in parallel mode and has an average outdoor temperature of −8.56 °C; the third period uses soil source heat pumps to operate separately; and the fourth period operates in series mode and has an average outdoor temperature of −11.32 °C. Operation of the coupled system in four periods was simulated and analyzed, and the operational efficiency and energy saving of the system were analyzed using an actual commercial building in a cold region as an example. The results demonstrate that the ET–GSHP system’s overall energy consumption during the heating period is reduced by 4.34% when compared to the traditional GSHP systems; the system’s COP can maintain a high level throughout the heating period, with an average COP of 3.315; and the soil temperature at the conclusion of the heating period is 25 °C, which is 8.89 °C higher than that of the traditional GSHP system, providing a guarantee of summer heat return. The new ET–GSHP system significantly boosts the efficiency of the system’s operation, achieves effective coupling between various heat sources through multi-stage control, and offers improved energy-saving advantages. Full article

Cold forging is widely used in many industries. Multi-stage cold forming is usually utilized in forging fasteners. In this study, numerical simulation and experimental investigations were carried out on a five-stage cold-forming process for the manufacturing of low-carbon steel AISI 1010 relief valve regulating nuts. The forming process through five stages included preparation and centering for backward extrusion, backward extrusion over die pin, upset, backward extrusion over a moving punch, and piercing. The formability of the workpiece was studied, such as the effects on forming force response, maximum forming force, effective stress and effective strain distributions, metal flow patterns, and strength. A comparison of the forming forces obtained in the forming experiment with the numerical simulation results of the five-stage cold forming showed a good agreement with the trend of the forming force growth. For the maximum forming force and forming energy, the fourth stage of backward extrusion over the moving punch at the upper face was the largest among the five stages. The total maximum forming forces from the first to the fifth stages were numerically 440.9 kN and experimentally 449.4 kN, meaning the FE simulation and experimental results were in good agreement. The numerically simulated effective strain distributions were consistent with the experimentally tested hardness distributions. Highly compacted grain flow lines also resulted in higher hardness. The overall hardness of the workpiece formed by five-stage cold forming increased by 31% compared to the initial billet. The hardness of the workpiece increased with the forming stages, and the strain-hardening effect was obvious. The strength of the workpiece was significantly increased by five-stage cold forming. Full article

Late Mesozoic and Cenozoic geodynamics of the Arctic region is discussed in the context of possible mechanisms which provide multistage cyclic transformations and transport of carbon through crust and mantle. Geodynamic processes control the abiogenic generation of hydrocarbons and the patterns of their localization. Possible mechanisms of abiotic hydrocarbon generation are explained in the context of carbon transport from subduction zones to rifts and serpentinization of ultramafic rocks in the rifts in the case of the Laptev Sea and Gakkel Ridge areas. The carbon of shallow crust origin migrates with encapsulated fragments of marine sediments which are consumed in the Pacific subduction zone where they become destroyed and transformed by different chemical and physical processes. The resulting C-species are involved in mantle convection flows and reach the continental rifts of the Laptev Sea and the Gakkel mid-ocean ridge. Thus, the hydrocarbons formed in the crust and in the mantle acquire signatures of abiotic origin. According to the authors, the scale of manifestation of abiogenic methanogenesis in the lower parts of the lithosphere and in the upper mantle is not so wide. Numerous small (mm and fractions of the mm) particles of exogenous matter and dispersed carbon pulled into the mantle can only form a stable crustal geochemical plume that propagates in the plane of movement of convective flows. Indirectly, the scale of manifestation of this process can be judged by the volumes of degassing of hydrocarbon and carbon dioxide gases, as well as hydrogen and its compounds in the rift systems of the earth’s crust, which are extremely insignificant. However, in the cold seas of the Eastern Arctic, massive emissions of bubble methane of mixed genesis were found. As shown in the literature, the range of variability of stable isotopes of carbon and ¹⁴C of methane in certain areas of discharge associated with rifting demonstrates values (anomalously heavy ¹³C, and young ¹⁴C) that can be considered as examples of presumably abiogenic origin. Our work is mostly theoretical and suggests further discussion and improvement of the mechanism of formation of abiogenic hydrocarbons and the processes of their transformation. Full article

The analysis of structure and defective substructure of rail steel in uniaxial compression to a degree of 50% is carried out. It is revealed that cold hardening has a multi-stage character and is accompanied by fragmentations of pearlite grains which is in field as the degree of deformation increases and reaches ≈ 0.4 volume of the foil studied at ε = 50%. The fragments being formed in ferrite plates are separated by low-angle boundaries. The average size of the fragmented ferrite decreases from 240 nm at ε = 15% to 200 nm at ε = 50%. Concurrently with the ferrite fragmentation, fragments of cementite are also observed. It is found that the sizes of the cementite fragments are in a range of 15 to 20 nm and depend weakly on the degree of sample deformation. The cementite fragmentation is caused by deformation-induced carbon dissolution and dislocation-induced fracture. The carbon atoms diffuse from cementite crystal to dislocations, which move through an interplanar space to form particles of tertiary cementite at nanoscale (2–4 nm). It is found that the increase in the degree of deformation is accompanied by a decrease in the scalar and an excess dislocation density. A physical interpretation of the observations has been given. Full article

The trend towards lightweight design, driven by increasingly stringent emission targets, poses challenges to conventional joining processes due to the different mechanical properties of the joining partners used to manufacture multi-material systems. For this reason, new versatile joining processes are in demand for joining dissimilar materials. In this regard, pin joining with cold extruded pin structures is a relatively new, two-stage joining process for joining materials such as high-strength steel and aluminium as well as steel and fibre-reinforced plastic to multi-material systems, without the need for auxiliary elements. Due to the novelty of the process, there are currently only a few studies on the robustness of this joining process available. Thus, limited statements on the stability of the joining process considering uncertain process conditions, such as varying material properties or friction values, can be provided. Motivated by this, the presented work investigates the influence of different uncertain process parameters on the pin extrusion as well as on the joining process itself, carrying out a systematic robustness analysis. Therefore, the methodical approach covers the complete process chain of pin joining, including the load-bearing capacity of the joint by means of numerical simulation and data-driven methods. Thereby, a deeper understanding of the pin joining process is generated and the versatility of the novel joining process is increased. Additionally, the provision of manufacturing recommendations for the forming of pin joints leads to a significant decrease in the failure probability caused by ploughing or buckling effects. Full article

Byproducts obtained from fish processing account for up to 70% of their live weight and represent a large amount of unused raw materials rich in proteins, fats, minerals, and vitamins. Recently, the management of the use of predominantly cold-water fish byproducts has become a priority for many processing companies. This paper describes the biotechnological processing of byproducts of warm-water Cyprinus carpio skeletons into gelatins. A Taguchi experimental design with two process factors (HCl concentration during demineralization of the starting material and the amount of enzyme during enzyme conditioning of the collagen) examined at three levels (0.5, 1.0 and 2.0 wt%; 0.0, 0.1 and 0.2 wt% respectively) was used to optimize the processing of fish tissue into gelatin. Depending on the preparation conditions, four gelatin fractions were prepared by multi-stage extraction from the starting material with a total yield of 18.7–55.7%. Extensive characterization of the gel-forming and surface properties of the prepared gelatins was performed. Gelatins belong to the group of zero–low-medium Bloom value (0–170 Bloom) and low–medium viscosity (1.1–4.9 mPa·s) gelatins and are suitable for some food, pharmaceutical, and cosmetic applications. During processing, the pigment can be isolated; the remaining solid product can then be used in agriculture, and H₃PO₄Ca can be precipitated from the liquid byproduct after demineralization. The carp byproduct processing technology is environmentally friendly and meets the requirements of zero-waste technology. Full article

The deformation microstructures formed by novel multistage high-temperature thermomechanical treatment (HTMT) and their effect on the mechanical properties of austenitic reactor steel are investigated. It is shown that HTMT with plastic deformation at the temperature decreasing in each stage (1100, 900, and 600 °C with a total strain degree of e = 2) is an effective method for refining the grain structure and increasing the strength of the reactor steel. The structural features of grains, grain boundaries and defective substructure of the steel are studied in two sections (in planes perpendicular to the transverse direction and perpendicular to the normal direction) by Scanning Electron Microscopy with Electron Back-Scatter Diffraction (SEM EBSD) and Transmission Electron Microscopy (TEM). After the multistage HTMT, a fragmented structure is formed with grains elongated along the rolling direction and flattened in the rolling plane. The average grain size decreases from 19.3 µm (for the state after solution treatment) to 1.8 µm. A high density of low-angle boundaries (up to ≈ 80%) is found inside deformed grains. An additional cold deformation (e = 0.3) after the multistage HTMT promotes mechanical twinning within fragmented grains and subgrains. The resulting structural states provide high strength properties of steel: the yield strength increases up to 910 MPa (at 20 °C) and up to 580 MPa (at 650 °C), which is 4.6 and 6.1 times higher than that in the state after solution treatment (ST), respectively. The formation of deformed substructure and the influence of dynamic strain aging at an elevated tensile temperature on the mechanical properties of the steel are discussed. Based on the results obtained, the multistage HTMT used in this study can be applied for increasing the strength of austenitic steels. Full article