Search Results (146)

Driven by the combined effects of global warming and the urban heat island (UHI) effect, building energy consumption has been rising steadily in recent years. The photovoltaic-cool roof (PVCR) system has emerged as an effective solution for urban energy conservation and carbon reduction. However, existing research on the energy-saving benefits of PVCR remains relatively limited, and none of these studies have considered the interaction between photovoltaic modules and high-reflectivity roofs (also called cool roof, CR). Therefore, field experiments were conducted to compare the thermal performance of the PVCR system against that of three conventional roof configurations, including photovoltaic roof (PVR), asphalt roof (AR), and CR. The results demonstrate that the PVCR system achieves a remarkable daytime cooling effect, with a maximum temperature reduction of 29 °C compared to the AR system, and maintains lower temperature fluctuations throughout the entire day. In addition, the findings reveal that the photovoltaic modules exhibit a lower average temperature when installed on the cool roof, with a temperature decrease of 0.15 °C relative to the asphalt roof. A numerical model incorporating the photothermal interaction between a high-reflectivity surface and PV modules was developed and validated with experimental data. The numerical model considers the interactions between the photovoltaic (PV) modules and the high reflectivity surface, including shortwave radiation reflection, longwave radiative exchange, and convective heat transfer. The sensitivity analysis indicates that a change in the spacing and height of the PV arrays from 0.3 m to 0.5 m increases the relative energy-saving efficiency of the system. The conclusions drawn in this paper can provide a reference for the application of the PVCR system in hot-summer and cold-winter areas. Full article

As the work hardening rate increases during the cold drawing of non-heat-treated steel (NHT steel), a significant loss in ductility and toughness can occur, leading to reduced formability and part quality. In this study, a bidirectional drawing process consisting of alternating forward and reverse passes is proposed to mitigate these issues and enhance the mechanical performance of the steel. Mechanical property evaluations, including tensile testing and three-point bending tests, were conducted to assess the effects of bidirectional drawing compared to conventional unidirectional drawing. The results showed that the bidirectionally drawn wire maintained a similar tensile strength to that of the unidirectionally drawn wire at a 70% area reduction, while exhibiting a 12% improvement in elongation. Microstructural analysis revealed grain refinement and reduced texture anisotropy in the bidirectionally drawn specimens, contributing to the observed enhancement in ductility. These findings indicate that bidirectional drawing is a promising approach for improving the formability and overall quality of high-strength, NHT steel components. Full article

The study presents a comprehensive analysis of the effects of high temperatures (500 °C and 700 °C) on the microstructure, mechanical properties, and acoustic emission (AE) parameters of cold-drawn prestressing steel. The investigations included mechanical testing, AE signal acquisition, and numerical verification using the finite element method (FEM). It was demonstrated that increasing temperature leads to significant microstructural changes (pearlite spheroidisation, carbide coarsening), resulting in strength degradation and a shift in the failure mechanism from quasi-brittle (initial state) to transitional (500 °C), and finally to ductile (700 °C). For the first time, AE parameters (Counts to Peak and RA-value) were correlated with local axial strains ε₂₂ and von Mises equivalent stress, enabling the identification of the moment of onset load-bearing capacity loss and the determination of critical material damage thresholds. A multi-criteria diagnostic indicator was proposed to assess the condition of prestressing steel after fire exposure. The results confirm the high potential of AE as a non-invasive tool for evaluating the safety of prestressing tendons and cables in reinforced concrete structures subjected to overheating or fire. Full article

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

This study investigated the corrosion behavior of cold-drawn Cu-0.43 wt% Mg alloy wires, which were intended for high-speed railway contact lines, under varying temperature (30–50 °C) and relative humidity (85% and 93%) conditions in controlled humid heat environments. The corrosion resistance of the alloy wires after 48 h of humid heat testing was evaluated using electrochemical methods such as polarization curves and electrochemical impedance spectroscopy. The morphology and composition of the corrosion products were characterized using scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results demonstrated superior corrosion resistance for specimens exposed to higher temperature and lower humidity (50 °C, 85% RH), as evidenced by lower corrosion current densities and higher film/charge transfer resistances compared to lower temperature and higher humidity conditions (30 °C, 93% RH). This enhanced resistance correlated with the formation of denser, more continuous protective corrosion films observed under high-temperature and low-humidity conditions. Surface analyses confirmed that the corrosion films consisted primarily of copper oxides (Cu₂O and CuO), with only trace amounts of magnesium oxides detected, suggesting Mg played a minor role in the composition of the mature passive film under these conditions. These findings provide crucial data on the environmental degradation behavior of Cu-Mg contact wires, which is particularly relevant for applications in coastal or humid regions. Full article

Introduction: Despite global improvements in immunization, major gaps persist. By 2024, an estimated 14.3 million infants, predominantly in low- and middle-income countries (LMICs), remained zero-dose (ZD), never having received even the first DTP vaccine. In 2022, 33 million children missed their measles vaccination (22 million missed the first dose, 11 million missed the second dose), highlighting entrenched structural, behavioral, and systemic barriers that continue to exclude marginalized populations. Addressing these inequities requires innovative, context-adapted approaches that strengthen primary health care (PHC) and extend services to the hardest-to-reach populations. Objectives: This study aims to document and synthesize implementation research (IR) projects on immunization programs in LMICs, identifying key enablers and effective strategies that reduce inequities, improve outcomes, and support efforts to reach ZD children. Methods: We conducted a retrospective multiple-case study of 36 IR projects across 13 LMICs, embedded within an evidence review framework and complemented by policy analysis. Data were drawn from systematic document reviews and validation discussions with project leads. A total of 326 strategies were extracted, coded using a structured codebook, and mapped to the WHO–UNICEF PHC Levers for Action. Descriptive analysis synthesized patterns across service delivery and policy outcomes, including coverage gains, improved microplanning, community engagement, and system integration. Results: Of the 326 immunization strategies identified, most (76.1%) aligned with operational PHC levers, particularly monitoring and evaluation (19.3%), workforce development (18.7%), and models of care (12%). Digital technologies (11.7%) were increasingly deployed for real-time tracking and oversight. Core strategic levers comprised 23.9% of strategies, with community engagement (8.9%) and governance frameworks (7.7%) emerging as critical enablers, though sustainable financing (4%) and private-sector engagement (0.9%) were rarely addressed. While the majority of projects focused on routine immunization (n = 32), only a few directly targeted ZD children (n = 3). Interventions yielded improvements in both service delivery and policy outcomes. Improvements in microplanning and data systems (23.5%) reflected the increased uptake of digital dashboards, GIS-enabled tools, and electronic registries. Community engagement (16.2%) emphasized the influence of local leaders and volunteers in building trust, while health system strengthening (15.7%) invested in cold chain, supervision, and workforce capacity. Coverage gains (10.6%) were achieved through delivery innovations, though sustainable financing remained a critical problem (3.4%). Conclusions: Reaching ZD children requires equity-driven strategies that combine digital innovations, community engagement, and resilient system planning. Sustained progress depends on strengthening governance, financing, and research. Embedding IR in immunization programs generates actionable evidence, supports context-specific strategies, and reduces equity gaps, offering practical insights that complement health system research and advance the Immunization Agenda 2030. Full article

This study investigates the influence of Cu addition on the nanostructural evolution and mechanical performance of a heavily drawn non-equiatomic CoCu_1.71FeMnNi high-entropy alloy (HEA) wire. Through systematic microstructural and compositional analysis, we examine how Cu constituent affects phase separation behavior and promotes deformation-induced nano-twinning in another phase counterpart. The designed HEA wire exhibits an elongated ultrafine dual face-centered cubic (fcc) lamella structure (i.e., Co-Fe-rich and Cu-rich phases) that emerges through compositional segregation by spontaneous phase separation from the as-cast state. High-resolution electron microscopy reveals the dislocation wall boundaries stabilized by nanoscale phase interfaces. The cold-drawn CoCu_1.71FeMnNi wire features an impressive combination of strength and ductility, as well as an ultimate tensile strength of nearly ~2 GPa with an elongation of over ~6%. These findings highlight the critical role of compositional tuning in controlling the ultrafine lamella structure stabilized by spinodal-like phase decomposition, offering a pathway to engineering high-performance HEA wires for advanced structural applications. Full article

The concept of “material effort” appears in continuum mechanics wherever the response of a material to the currently existing state of loads and boundary conditions loses its previous, predictable character. However, within the material, which still descriptively remains a continuous medium, new physical structures appear and new previously unused physical features of the continuum are activated. The literature is dominated by a simplified way of thinking, which assumes that all these states can be characterized and described by one and the same measure of effort—for metals it is the Huber–Mises–Hencky equivalent stress. Quantitatively, perhaps 90% of the literature is dedicated to this equivalent stress. The remaining authors, as well as the author of this paper, assume that there is no single universal measure of effort that would “fit” all operating conditions of materials. Each state of the structure’s operation may have its own autonomous measure of effort, which expresses the degree of threat from a specific destruction mechanism. In the current energy sector, we are increasingly dealing with “low-cycle thermal fatigue states”. This is related to the fact that large, difficult-to-predict renewable energy sources have been added. Professional energy based on coal and gas units must perform many (even about 100 per year) starts and stops, and this applies not only to the hot state, but often also to the cold state. The question arises as to the allowable shortening of start and stop times that would not to lead to dangerous material effort, and whether there are necessary data and strength characteristics for heat-resistant steels that allow their effort to be determined not only in simple states, but also in complex stress states. Do these data allow for the description of the material’s yield surface? In a previous publication, the author presented the results of tension and compression tests at elevated temperatures for two heat-resistant steels: St12T and 26H2MF. The aim of the current work is to determine the properties and strength characteristics of these steels in a pure torsion test at elevated temperatures. This allows for the analysis of the strength of power turbine components operating primarily on torsion and for determining which of the two tested steels is more resistant to high temperatures. In addition, the properties determined in all three tests (tension, compression, torsion) will allow the determination of the yield surface of these steels at elevated temperatures. They are necessary for the strength analysis of turbine elements in start-up and shutdown cycles, in states changing from cold to hot and vice versa. A modified testing machine was used for pure torsion tests. It allowed for the determination of the sample’s torsion moment as a function of its torsion angle. The experiments were carried out at temperatures of 20 °C, 200 °C, 400 °C, 600 °C, and 800 °C for St12T steel and at temperatures of 20 °C, 200 °C, 400 °C, 550 °C, and 800 °C for 26H2MF steel. Characteristics were drawn up for each sample and compared on a common graph corresponding to the given steel. Based on the methods and relationships from the theory of strength, the yield stress and torsional strength were determined. The yield stress of St12T steel at 600 °C was 319.3 MPa and the torsional strength was 394.4 MPa. For 26H2MH steel at 550 °C, the yield stress was 311.4 and the torsional strength was 382.8 MPa. St12T steel was therefore more resistant to high temperatures than 26H2MF. The combined data from the tension, compression, and torsion tests allowed us to determine the asymmetry and plasticity coefficients, which allowed us to model the yield surface according to the Burzyński criterion as a function of temperature. The obtained results also allowed us to determine the parameters of the Drucker-Prager model and two of the three parameters of the Willam-Warnke and Menetrey-Willam models. The research results are a valuable contribution to the design and diagnostics of power turbine components. Full article

This study presents the development of a deep drawing process under an indirect hot stamping method for manufacturing an automotive internal combustion engine oil pan from ultra-high-strength steel (UHSS) sheets, specifically 22MnB5. The forming process involves two stages—cold stamping followed by hot stamping—and is finalized with rapid quenching to achieve a martensitic microstructure. Finite element simulation using AutoForm R8 was conducted to determine optimal forming conditions. The simulation results guided the design of the forming tools and were validated through experimental trials. The final oil pan component exhibited no cracks or wrinkles, with maximum thinning below 18%, a hardness of 550.63 HV, and a fully martensitic phase. This research demonstrates a novel and effective solution for producing deep-drawn, high-strength components using indirect hot stamping, contributing to the advancement of automotive forming processes in Thailand. Full article

This study investigates the microstructural evolution and mechanical degradation mechanisms of cold-drawn 310S stainless steel subjected to repeated thermal cycling between 900 °C and room temperature. The results reveal that thermal cycling induces significant lattice distortion, dislocation accumulation, and recrystallization, leading to grain refinement and increased tensile strength. However, these microstructural changes also initiate subsurface cracks and reduce ductility. TGA analysis confirms thermal weight loss from decarburization, especially under oxidative atmospheres. EPMA analysis and tensile tests after thermal cycling reveal that surface cracks formed during thermal cycling act as origins for transgranular crack propagation under tensile stress, significantly reducing fracture resistance. Bending fatigue tests further demonstrate that thermally fatigued specimens exhibit inferior fatigue life compared to raw material, confirming the deteriorating mechanical properties of 310S stainless steel after thermal cycling. Overall, the combined effects of thermal and mechanical fatigue degrade the structural integrity of 310S stainless steel, revealing that lattice distortion and subsurface cracking are the key factors in its embrittlement and reduced fatigue performance. Full article

Background: Health departments disseminate health education related to influenza to the public through various media in China. We examined knowledge, attitudes, and practices regarding influenza and the influenza vaccine (KAP-flu) over time among pregnant women (PW) compared to non-PW. Methods: A cross-sectional survey was conducted in Suzhou, China in 2013 and 2023. We included and interviewed PW seeking prenatal care and excluded PW there for non-routine visits. The comparison group was drawn from non-PW seeking physical examinations at the same facilities. Stratified cluster sampling was used to enroll participants from the various levels of prenatal-care facilities. Results: In 2013, we surveyed 1673 PW and 401 non-PW, and in 2023, we surveyed 2195 PW and 1171 non-PW. The proportion of PW who had ever heard of the influenza vaccine showed no significant change, at 56% in 2013 and 57% in 2023; by contrast, there was a significant increase among non-PW (55% to 78%). The proportion of pregnant participants who knew when to get vaccinated dropped from 14% to 12%, in contrast to the increase among non-PW (6% to 20%). The proportion of PW who believed that the influenza vaccine is effective dropped from 91% in 2013 to 76% in 2023, in contrast to the stable value among non-PW (84% to 82%). In 2023, pregnant participants exhibited lower levels of knowledge about both influenza disease and the influenza vaccine, along with less positive attitudes toward the effectiveness and safety of the vaccine. They also showed lower willingness to vaccinate and lower vaccination rates compared to non-pregnant participants. Concerning KAP-flu among PW, less than half recognized that influenza is different from a common cold; fewer than one in five understood the timing and frequency of vaccination or the policy prioritizing PW for influenza vaccination; vaccination coverage remained below 2% over time. Conclusions: PW had concerning gaps in knowledge and attitudes regarding influenza and the influenza vaccine compared to non-PW in Suzhou, China. Specific actions targeting PW, such as initiatives leveraging the maternal and child healthcare system, are warranted to reduce the gaps. Full article

Post-processing plays a vital role in the determination of the final structures and properties of oriented materials. As a sustainable candidate of oil-based poly(ethylene terephthalate), biobased poly(ethylene 2,5-furandicarboxylate) (PEF) reflects great promise in green fiber, film, and packaging applications, but it undergoes poor stress-induced crystallization (SIC) under tensile deformation, necessitating a post-processing technique to improve its crystallinity and stability. Here, the structural evolution of pre-stretched PEF under post heating after uniaxial deformation was monitored by online synchrotron X-ray diffraction/scattering, differential scanning calorimetry, and ex situ infrared spectroscopy. The results delineate the significantly enhanced crystallization of pre-deformed PEF that happened far below its cold crystallization temperature. Through the isochronous analyses of the temperature-dependent evolution of mechanical response, the mesophase, crystal structure, orientation factor, chain conformation, and interchain ═C−H···O═C hydrogen bonding, the molecular mechanisms of microstructural transition and oriented crystallization of pre-drawn PEF under post heating were clarified. This research can enhance the understanding of PEF crystallization in an oriented state and provide guidelines on the structural design and technical control for processing high-performance PEF-based materials. Full article

Straw as a building material alternative is in line with sustainable development goals. To make effective use of straw resources such as rice and corn stalks in rural areas, a kind of steel wire mesh-reinforced straw concrete sandwich panel (SCSP) was developed. The SCSP was composed of cold-drawn low-carbon steel-wire mesh (SWM), fine gravel concrete (FGC), and straw. The used type of FGC was shotcrete. A cold-drawn low-carbon SWM was arranged on the upper and lower sides of the SCSP, and a vertical wire tie was arranged between the upper and lower cold-drawn low-carbon SWMs. The FGC was sprayed on the SWM to make the SCSP layer work together. The loading process of the SCSP could be divided into three stages: elastic working state, cracking state, and failure state. The results of the four-point loading test show that the maximum flexural moment of the SCSP can be up to 7.5 kN·m in the elastic range. The ultimate bearing capacity of SCSP reaches 10.9 kN·m, and the maximum crack width can reach 3~4 mm. At the same time, based on the assumption of the flexural section of SCSP, two simplified calculation models of SCSP bearing capacity were established. The average error was 2.99% and 9.41%, respectively, by comparing the experimental values with the two calculated values. The results obtained by using the two models were in good agreement with the experimental results. Full article

This article presents the simulation results of synchronization of a permanent magnet synchronous generator (PMSG) dedicated for a hydroelectric plant without power converter devices. The proposed machine design allows to connect a generator to the grid in two different ways. With the first method, the machine is connected to the grid in a similar way as in the case of an electrically excited synchronous generator. The second method is a direct line-start process based on asynchronous torque—similar to asynchronous motor start. Both methods can be used alternately. The advantages of the presented design are elimination of converter devices for starting the PMSG, possibility of use in small and medium hydroelectric power plants, operation with a high efficiency and high power factor in a wide range of generated power, and smaller dimensions in comparison to the generators currently used. The described rotor design allows for the elimination of capacitor batteries for compensation of reactive power drawn by induction generators commonly used in small hydroelectric plants. In addition, due to the high efficiency of the PMSG, high power factor, and appropriately selected design, the starting current during synchronization is smaller than in the case of an induction generator, which means that the structural elements wear out more slowly, and thus, the generator’s service life is increased. In this work, it is shown that PMSG with a rotor cage should have permanent magnets with an increased temperature class in order to avoid demagnetization of the magnets during asynchronous start-up. In addition, manufacturers of such generators should provide the number of start-up cycles from cold and warm states in order to avoid shortening the service life of the machine. The main objective of the article is to present the methods of synchronizing a generator of such a design (a rotor with permanent magnets and a starting cage) and their consequences on the behavior of the machine. The presented design allows synchronization of the generator with the network in two ways. The first method enables synchronization of the generator with the power system by asynchronous start-up, i.e., obtaining a starting torque exceeding the braking torque from the magnets. The second method of synchronization is similar to the method used in electromagnetically excited generators, i.e., before connecting, the rotor is accelerated to synchronous speed by means of a water turbine, and then, the machine is connected to the grid by switching on the circuit breaker. This paper presents electromagnetic phenomena occurring in both cases of synchronization and describes the influence of magnet temperature on physical quantities. Full article

This paper focuses on the study of the tensile fracture behaviour of prismatic notched specimens of cold drawn pearlitic steel, providing a macro- and micro-approach. Two types of notched samples with very different notch radius (sharp and blunt notches, PAA and PCC) and the same notch depth were studied, thereby allowing a study of the fracture behaviour under different levels of stress triaxiality (constraint) in the experimental specimen. The studied samples are machined from pearlitic steel wires taken from a real cold drawing chain, analysing the entire drawing process, from the initial base material (hot rolled bar; not cold drawn at all) to the final commercial product (prestressing steel wires; heavily cold drawn), including two intermediate stages in the manufacture chain. The aforesaid specimens were subjected to tensile fracture tests and analysed at macroscopic and microscopical level using the scanning electron microscope (SEM), thereby obtaining micrographs of the different areas appearing in the specimens under study and assembling full micro-fracture maps (MFMs) of the fractured area. The aim of the research is to analyse the macro- and microscopic changes produced by the variation in stress triaxiality state (constraint), along with the different fracture processes. The first relevant finding is the increase in fracture path deflection for higher drawing degrees, and for greater triaxiality levels associated with sharp notches. Another finding is the variation in area of the different fracture zones, i.e., outer crown (OC), fracture process zone (FPZ) and intermediate zone (Z_INT), which are characterised by their specific micro-mechanisms, micro-void coalescence (MVC), cleavage (C) and special (large) micro-void coalescence (MVC*). The higher the stress triaxiality level, the larger the area occupied by the Z_INT in the fracture process. The fracture behaviour tends to unify along with the degree of drawing, with less dependence on the state of triaxiality imposed on heavily drawn wires. Results have been obtained in which the increase in triaxiality, imposed by the smaller radius of curvature of the notch (sharp notch), as well as the greater degree of drawing of the wires, cause the fracture process to place the FPZ at the notch tip. It is demonstrated that the variation in stress triaxiality and the drawing degree can generate different locations of the fracture initiation zone (FPZ). Full article