bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of critical local straining conditions for solidification cracking at laser beam welding by experimental and numerical methods
Authors: Bakir Nasim , Gumenyuk Andrey , Rethmeier Michael 
Published: September 2024

AbstractThe phenomenon of solidification cracking has been the subject of numerous research projects over the years. Great efforts have been made to understand the fundamentals of hot cracking. It is generally agreed that solidification cracks form in the solidification range between the liquidus and solidus temperatures under the combination of thermal, metallurgical and mechanical factors. There is still a need to determine the time‐resolved strain distribution in the crack‐sensitive region in order to analyse the local critical conditions for solidification cracking phenomena. This was a strong motivation for the development of a measurement system used in this study to estimate the local strains and strain rates in the zone where the solidification crack is expected to occur. The laser beam welding experiments were conducted using the Controlled‐Tensile‐Weldability test (CTW test) to apply an external strain condition during welding to generate solidification cracks. The CTW test is a test method for investigating the susceptibility of laser‐welded joints to solidification cracking, in which the sample can be subjected to a defined strain at a defined strain rate during welding.In combination with experimental investigations, numerical simulations provide spatially detailed and time‐dependent information about the strain development during the welding process, especially regarding the critical conditions for solidification cracking. Therefore, this tool was also used in the present study to evaluate the accuracy of measurement methods and to estimate experimentally derived values and their concrete influence on the formation of solidification cracks. By integrating experimental methods and numerical simulations, this study investigates the spatially resolved and temporally changing development of strain during welding, with a particular focus on the critical conditions that lead to the formation of solidification cracks. The use of numerical simulations serves a dual purpose by validating the accuracy of measurement methods and examining experimentally determined values for their actual influence on the formation of solidification cracks. A three‐dimensional finite element (FE) model implemented with ANSYS is used to simulate strains and stresses during welding. The credibility of the model was first established by validation using experimental temperature measurements. Subsequently, structural simulations were carried out under external load. The results of the simulations showed commendable agreement with the strain measurements performed using the developed technique.
Numerical detection of shaft misalignments using a sensor‐integrating jaw coupling
Authors: Menning Johannes D. M. , Ewert Arthur , Prokopchuk Artem , Vorrath Ernst‐Friedrich Markus , Schlecht Berthold , Wallmersperger Thomas 
Published: September 2024

AbstractShaft misalignments are one of the main causes of damage to couplings in machines. If they are not detected in time, they can lead to machine downtimes. When assembling a machine, however, it is not always possible to align the shafts perfectly. Elastic couplings are able to compensate for such misalignments up to a certain degree. To detect the present radial misalignment, the concept of a sensor‐integrating jaw coupling, developed to determine the transmitted torque, is used. In the teeth of the gear rim, boreholes are drilled and dielectric elastomer sensors (DES) are inserted. If the teeth deform during use of the coupling the DES will deform as well, leading to a change in capacitance, which can be detected. If the two shafts, which the coupling connects, are perfectly aligned to each other, each of the loaded teeth will deform uniformly. However, if there is a radial or angular misalignment, the deformation is different for each tooth, which can be determined with the help of the DES. To demonstrate this effect, a finite element model of the sensor‐integrating jaw coupling with misalignments is created, and numerical simulations are conducted. In this model, the hyper‐viscoelastic material behavior of (i) the gear rim of the jaw coupling and (ii) the DES is taken into account. From the mechanical simulation, the deformed state of the DES is obtained, which is used to compute the capacitance of the sensor. With the results of the numerical simulations, a symbolic regression is performed. The result is an analytical formula that makes the accurate detection of the present radial misalignment possible. The developed framework can later be easily programmed on a microcontroller which is integrated in the sensor‐integrating jaw coupling.
Natural riparian vegetation as corridors to promote bee diversity and pollination services in an urban landscape
Authors: Lan Yang , Zhao Qing , Zhang Xin , Huang Junlong , Shao Ying , Chen Zhongli 
Published: September 2024

Abstract

Understanding how landscape structure and riparian vegetation impact bee diversity is important for maintaining pollination service in urban areas. We explored spatial and temporal variation of bee communities across land use types in a riparian zone of a mountainous megacity in 2018 and 2022, examined whether riparian vegetation functions as corridors that maintain gene flow of bee populations, and mapped pollination supply at the landscape scale.

Pielou index was higher in 2018 than in 2022, while no significant differences in abundance, Shannon and richness index were observed. The abundance of bees and the Shannon index were significantly and positively correlated with the abundance of flowers on grassland and forested land, respectively, while both were negatively correlated with the area of the building.

The genetic differentiation of the bee communities in the riparian zone was lower than those outside, indicating the function of the riparian vegetation corridor. The pollination supply varied significantly between regions, with medium to high degree of pollination supply distributed primarily in residual habitats and the surrounding urban green spaces, while low degree in the remaining areas.

Our results stress the importance of maintaining the continuity of vegetation in riparian zones and increasing flower abundance, especially native plant species, for the conservation of bees in urban areas.

Read the free Plain Language Summary for this article on the Journal blog.
Tribological properties of perfluoropolymer fiber filled carbon fiber/polyphenylene sulfide composites: Effect of in‐situ fibrillated fiber or split fiber
Authors: Qiu Xiaotao , Luo Bin , Gu Aiqun , Tang Wenjian , Xie Meiju , Tang Siqi , Yu Zili 
Published: September 2024

AbstractIn this study, carbon fiber (CF) filled polyphenylene sulfide (PPS) composites are lubricated with perfluoropolymer (PFP) fiber by melt‐blending. The effect of double fibers (CF‐PFP fibers) on the tribological properties of PPS composites has been carefully investigated and correlated under various sliding conditions. The results indicated that the tribological performance of PPS composites with double fibers is better than that of the composites with a single fiber, especially under severe conditions. Mechanism exploration suggests that a double‐fiber hybrid structure between a hard CF and a soft PFP fiber could tightly entrap the CF by fibril entanglement, thus preventing the CF from being stripped out of the matrix under the steel ring shearing force. Under optimized conditions, the average friction coefficient of composites with PFP fiber is only about 0.1 at 300 N load under 200 rpm, even lower than half of the average friction coefficient of the composites with PTFE powder under the same condition. Notably, compared to commercial split PFP fibers, the in‐situ formed PFP fibers with more uniform distribution significantly improve the tribological properties. This work open up a novel perspective for improving the tribological performance of composites by systematically regulating the microstructure of self‐lubricating fibrous additives.Highlights
PFA is subject to in‐situ fibrillation during melt blending.
Fibrous PFP effectively improves the tribological properties of PPS/CF composites.
The in‐situ formed PFP fiber contributes to better tribological properties.
The double‐fiber hybrid structure prevents the CF from being sheared out.
The number of processing cycles affects the tribological properties.
Effect of crystallization behavior on wear properties of polytetrafluoroethylene composites modified by irradiation above melting point
Authors: Wang Xiaojie , Huang Geng , Zhou Shuangquan , Wang Junyi , Wu Daming , Gao Xiaolong 
Published: September 2024

AbstractIn this paper, the reasons for the improved wear resistance of irradiation‐modified Polytetrafluoroethylene (RM‐PTFE) and its composites above the melting point were investigated from the microcrystalline point of view by using methods such as crystallization kinetics, and it was found that the linear wear rate of RM‐PTFE was only 0.3 um/km, with a 1000 times increase in wear resistance, which was due to the transformation of its crystals from flake crystals that were easily dislodged to spherical crystals that were more resistant to abrasion. It was also found that the linear wear rate of Polytetrafluoroethylene (PTFE) with coke and graphite was 0.2 and 0.1 μm/km, respectively, and the abrasion resistance was further improved, which was attributed to the lowering of spherical crystal grain size by coke and graphite, which had better mechanical properties. These studies lay the foundation for future research on the frictional wear mechanism of RM‐PTFE above the melting point.Highlights
Irradiation‐modified PTFE above the melting point
Wear resistance of PTFE increases 1000 times
Changes in crystal morphology dramatically increase wear resistance
Use of crystallization kinetics to study the crystalline form of PTFE
Small grain size improves wear resistance
Research on defect identification of carbon fiber composite materials based on ultrasonic phased array
Authors: Jing Ziang , Cai Gaoshen , Yu Xiang , Wang Bingxu 
Published: September 2024

AbstractIt is more and more difficult to identify defects in carbon fiber composite materials due to the difficulty in making defect samples and the single signal analysis method. In order to better solve the problem of defect identification in carbon fiber composite materials, this study uses ultrasonic phased array equipment to quantitatively locate and detect carbon fiber composite laminates with embedded delamination defects, so as to more intuitively and effectively display the appearance of different delamination defects. The time domain analysis of the collected ultrasonic original signal and the time‐frequency domain analysis using wavelet packet are carried out. A total of 6 eigenvalues were extracted to reflect the ultrasonic signals of different delamination defects. By using genetic algorithm to optimize BP neural network, the recognition accuracy of delamination defects of different sizes is more than 95%, and the recognition accuracy of delamination defects of different depths is 100%, so as to realize the effective intelligent recognition of delamination defects of different sizes and depths of carbon fiber composites. This study is of great significance to improve the accuracy and reliability of defect identification of carbon fiber composite materials.Highlights
The ultrasonic phased array equipment is used to quantitatively locate the carbon fiber composite laminates with embedded delamination defects, so that the appearance of different defects can be displayed more intuitively and effectively.
Using time domain analysis and time‐frequency domain analysis based on wavelet packet, the combination of the two can more comprehensively extract the effective features of the defect signal.
The BP neural network is optimized by genetic algorithm, and the results can effectively and automatically identify different layered defects, which lays a good foundation for the rapid and accurate identification of more defects in the future.
Enhanced Hyperpolarizabilities Through p‐Phenylene Bridges: Computational Studies on Metamerism and Functional Molecular Properties of Pyridinium–Dicyanomethanide‐Based Zwitterions
Authors: Sitha Sanyasi 
Published: September 2024

ABSTRACTPara‐phenylene‐bridged pyridinium (acceptor)–dicyanomethanide (donor)‐based zwitterions were computationally investigated and are reported here. Reichardt's metamer was found to be twisted and Brooker's metamer in near‐planar conformation. Natural bond orbital (NBO) analysis showed that mesomeric resonance is helping Brooker's metamer but found to be not helpful for Reichardt's metamer. To assess the impacts of metamerism and aromatic bridges, fundamental molecular properties like dipole moments (μ), polarizabilities (α), hyperpolarizabilities (β), and adiabatic absorptions of these two molecules were analyzed and then directly compared with their counterpart zwitterions without any bridges (previously reported). Results of impact of metamerism: Reichardt's metamer showed around three times enhanced hyperpolarizabilities (ωB97xD: β = 1577.1 × 10−30 esu) than the Brooker's metamer (ωB97xD: β = 532.5 × 10−30 esu). Impacts of p‐phenylene bridges: Compared to their respective D–A directly connected zwitterions reported previously (in ωB97xD methodology, Reichardt's: β = 257.2 × 10−30 esu and Brooker's: β = 67.2 × 10−30 esu), respective p‐phenylene‐bridged zwitterions showed five to eight times enhanced hyperpolarizabilities. This report highlights the better efficiencies of Reichardt's metamer over Brooker's metamer and aromatically bridged over the directly connected zwitterions. Current findings may be helpful in the designing of efficient functional molecular chromophores, and aromatic bridge combined with zwitterions can be solutions to nonlinear transparency trade‐off problem.
The causal relationship between drinking water and gastrointestinal cancers: a two‐sample mendelian randomization analysis
Authors: Gui Liang , Wang Jian 
Published: September 2024

AbstractCancers of the digestive tract are a series of diseases that seriously affects the health and life quality of the population worldwide, and the etiology is closely related to various daily habits. Drinking water is a daily human activity, but the intrinsic connection between water intake and gastrointestinal (GI) cancers is still unclear. We used the two‐sample mendelian randomization (TSMR) method to explore the potential causal relationship between water consumption and GI cancers. We obtained the integrated GWAS data of water intake (ukb‐b‐14 898), as well as the GWAS results of oral cavity cancer (ieu‐b‐4961), esophageal cancer (ebi‐a‐GCST90018841), gastric cancer (ebi‐a‐GCST90018849), liver cancer (ieu‐b‐4953), hepatic bile duct cancer (ebi‐a‐GCST90018803), pancreatic cancer (ebi‐a‐GCST90018893) and colorectal cancer (ebi‐a‐GCST90018588) through the online database “IEU OPEN GWAS PROJECT”. Using inverse variance weighting (IVW) method, weighted median method, MR Egger regression method, simple model method, and weighted model method to jointly study the causal relationship between water intake and GI cancers. Mendelian randomization analysis showed a negative correlation between water consumption and esophageal cancer (weighted media, OR = 0.215, p = .021; MR Egger, OR = 0.033, p = .040; weighted mode, OR = 0.162, p = .045), a positively association with pancreatic cancer (IVW, OR = 2.663, p = .033). There is a potential positive correlation between water intake and gastric cancer as well as colorectal cancer, but not statistically significant. The associations between water intake and oral cavity cancer, liver cancer and hepatic bile duct cancer remain uncertain. Therefore, Increased amount of drinking water may help to prevent the incidence of esophageal cancer, but might promote the development of pancreatic cancer.
Quantum Effect Enables Large Elastocaloric Effect in Monolayer MoSi2N4${\rm MoSi}_2{\rm N}_4$ and Graphene
Authors: Yin Yan , He Weiwei , Tang Wei , Yi Min 
Published: September 2024

AbstractLow‐dimensional materials with outstanding heat conductivity and elastocaloric effect (eCE) are significant for environmentally friendly and energy‐efficient nano refrigerators. However, most of elastocaloric materials with first/second‐order phase transition suffer from hysteresis loss. Herein, an emerging monolayer is theoretically demonstrated as a promising candidate, which exhibits no hysteresis loss enabled by reversible elastic response, as well as large eCE and high eC strength enabled by quantum effect (QE). Considering the remarkable influence of QE and thermo‐mechanical coupling (TMC) in the monolayer limit, the adiabatic temperature change () is evaluate by incorporating QE and TMC. Molecular dynamics simulation significantly underestimates , whereas method with QE slightly overestimates when compared to method with QE+TMC. At 300 K, of is –(11–42) K under biaxial tensile forces of 26–84 nN. The elastocaloric coefficients are –(0.3–0.9) , comparable to that of armchair carbon nanotubes. A large eCE ( around 15 K under a biaxial tensile load of 35 nN) is also revealed for graphene by incorporating QE and TMC. This study proposes a more comprehensive method for quantitatively predicting eCE in 2D materials by including QE and TMC, offering a theoretical guideline for refrigerating materials in the monolayer limit.
Magnetic Micromotors with Spiky Gold Nanoshells as SERS Sensors for Thiram and Bacteria Detection
Authors: Yang Tao , Zhou Jianping , Wang Yongkang , Fan Ben , Qiao Jing , Chen Lixiang , Wang Xiaoyu , Guo Lingxiang , Yang Hong , Li Quan 
Published: September 2024

AbstractSurface‐enhanced Raman scattering (SERS) is widely used in all kinds of detection due to its ultrahigh sensitivity and selectivity. Micromotors, when used as SERS sensors, or the so‐called “hotspots on the fly”, can combine both controlled mobility and SERS sensing capacity, and are ideal for versatile in situ detection. In this work, mobile SERS sensors are successfully fabricated by growing gold nanospikes onto magnetic microsphere surfaces. These mobile micromotors can act as normal SERS sensors, characterized by the trace detection of thiram, a highly toxic fungicide. The detection limit can reach 0.1 nM, as good as most other noble metal deposited substrates. With significant magnetic gradient forces, separation of pathogenic bacteria from bulk solution is achieved once these magnetic micromotors bind with bacterial cells. Manipulated propulsion of micromotors, on the other hand, enables them to approach and contact pathogenic bacterial cells on command and further acquire Raman spectra under a controlled degree of contact, a capability never seen with passive sensors. The robotic SERS sensors have demonstrated unique sensing characteristics with controlled manipulations along with discriminative detection between bacterial species.
Exploring the Adaptability of 4D Printed Shape Memory Polymer Featuring Dynamic Covalent Bonds
Authors: Zhang Jing , Xu Mingkun , Zhang Nan , Tao Liming , Shao Mingchao , Wang Tingmei , Yang Zenghui , Wang Qihua , Zhang Yaoming 
Published: September 2024

Abstract4D printing (4DP) of high‐performance shape memory polymers (SMPs), particularly using digital light processing (DLP), has garnered intense global attention due to its capability for rapid and high‐precision fabrication of complex configurations, meeting diverse application requirements. However, the development of high‐performance dynamic shape memory polymers (DSMPs) for DLP printing remains a significant challenge due to the inherent incompatibilities between the photopolymerization process and the curing/polymerization of high‐strength polymers. Here, a mechanically robust DSMP compatible is developed with DLP printing, which incorporates dynamic covalent bonds of imine linking polyimide rigid segments, exhibiting remarkable mechanical performance (tensile strength ≈41.7 MPa, modulus ≈1.63 GPa) and thermal stability (Tg ∼ 113 °C, Td ∼ 208 °C). More importantly, benefiting from the solid‐state plasticity conferred by dynamic covalent bonds, 4D printed structures demonstrate rapid network adaptiveness, enabling effortless realization of reconfiguration, self‐healing, and recycling. Meanwhile, the extensive π‐π conjugated structures bestow DSMP with an intrinsic photothermal effect, allowing controllable morphing of the 4D configuration through dual‐mode triggering. This work not only greatly enriches the application scope of high‐performance personalized configurations but also provides a reliable approach to addressing environmental pollution and energy crises.
Oscillations of the Local pH Reverses Silver Micromotors in H2O2
Authors: Liu Xianghong , Peng Yixin , Yan Zuyao , Cao Dezhou , Duan Shifang , Wang Wei 
Published: September 2024

AbstractAsymmetric chemical reactions on the surfaces of colloidal particles are known to propel them into directional motion. The dynamics of such chemical micromotors are sensitive to their local chemical environments, which also continually evolve with the reactions on motor surfaces. This two‐way coupling between the motor dynamics and the local environment may result in complex nonlinear behaviors. As an example, we report that Janus Ag microspheres, which self‐propel in hydrogen peroxide (H2O2), spontaneously reverse their direction of motion two or more times. We hypothesize that two distinct chemical reactions between Ag and H2O2 drive the micromotor in opposite directions, and which reaction dominates depends on the local pH. Interestingly, the local pH near a Ag micromotor oscillates spontaneously in H2O2, likely due to a complex interplay between the kinetics of the reaction between Ag and H2O2 and the diffusion of chemical species. Consequently, the pH‐sensitive Ag micromotor reverses its direction of motion in response to these pH oscillations. This study introduces a new mechanism for regulating the speed and directionality of micromotors, highlights the potential of Ag micromotors in chemical sensing, and sheds new light on the interplay between chemical kinetics and micromotor dynamics.
Subnational Institutional Differences and FDI Spillovers Behind the R&D–Performance Relationship in Russia
Authors: Lebedev Sergey , Peng Mike W. 
Published: September 2024

ABSTRACTThis study explores how subnational institutional differences in a large emerging economy—Russia—influence the relationship between research and development (R&D), foreign direct investment (FDI) spillovers, and firm performance. We find that the relationship between R&D and firm performance is positively moderated by subnational institutional development. Furthermore, we find that FDI will more positively moderate the relationship between R&D and firm performance if subnational institutional development is also higher, thus showing that subnational institutional development may foster the positive spillover effect of FDI on local firms.