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The 60 kg/m U75V rail serves as the predominant rail type within China’s high-speed rail network. This study comprehensively evaluates the fatigue behavior of U75V rails through experimental investigations encompassing monotonic tensile testing, high-cycle fatigue characterization, and fatigue crack propagation analysis. All specimens were extracted from standardized 60 kg/m high-speed rail sections to ensure material consistency. Firstly, monotonic tensile tests were conducted to determine the fundamental mechanical properties of the U75V rail. Secondly, uniaxial tension–compression fatigue tests were conducted to establish the S-N and P-S-N relationships of the U75V rail. Lastly, fatigue crack propagation analysis was carried out on three compact tension specimens under three incremental loading forces. Monotonic tensile test results demonstrated full compliance of the material’s basic mechanical properties with Chinese national standards. Fatigue crack propagation results indicated that the crack growth rate of the U75V rail was not only related to the stress-intensity range ∆K but was also correlated with the loading force range ∆F due to a typical crack tip shielding effect, i.e., plasticity-induced crack closure effect. The derived fatigue performance parameters and crack growth mechanism provide essential inputs for predictive fatigue life modeling of high-speed rail infrastructure and development of refined finite element models for fatigue analysis.

Working stress is an important indicator reflecting the health status of structures. Passive-monitoring technology using the piezoelectric effect can effectively monitor the dynamic stress of structures. However, under static loads, the charge generated by the piezoelectric devices can only be preserved when the external circuit impedance is infinitely large, which means passive-monitoring techniques are unable to monitor static and quasi-static stress caused by slow-changing actions. In current studies, experimental observations have shown that the impedance characteristics of piezoelectric devices are affected by external static loads, yet the underlying mechanisms remain inadequately explained. This is because the impedance characteristics of piezoelectric devices are actually dynamic characteristics under alternating voltage. Most existing impedance analysis models are based on linear elastic dynamics. Within this framework, the impact of static stress on dynamic characteristics, including impedance characteristics, cannot be addressed. Accounting for static stress in impedance modeling is a challenging problem. In this study, the static stress applied on an embedded piezoelectric plate is abstracted as the initial stress of the piezoelectric plate. Based on nonlinear elastic dynamic governing equations, using the displacement method, an impedance analysis model of an embedded piezoelectric plate considering initial stress is established and verified through a fundamental experiment and a finite element analysis. Based on this, the explicit analytical relation between initial stress and impedance characterizations is provided, the mechanism of the effect of initial stress on the impedance characterizations is revealed, and procedures to identify static stress using impedance characterizations is proposed. Moreover, the sensitivities of the impedance characterizations in response to the initial stress are thoroughly discussed. This study mainly provides a theoretical basis for monitoring static stress using the electromechanical impedance of an embedded piezoelectric plate. And the results of the present study can help with the performance prediction and design optimization of piezoelectric-based static stress sensors.

In the current electromechanical model of cantilevered piezoelectric energy harvesters, the assumption of uniform electric field strength within the piezoelectric layer is commonly made. This uniform electric field assumption seems reasonable since the piezoelectric layer looks like a parallel-plate capacitor. However, for a piezoelectric bender, the strain distribution along the thickness direction is not uniform, which means the internal electric field generated by the spontaneous polarization cannot be uniform. In the present study, a non-uniform electric field in the piezoelectric layer is resolved using electrostatic equilibrium equations. Based on these, the traditional distributed parameter electromechanical model is corrected and simplified to a practical single mode one. Compared with a traditional model adopting a uniform electric field, the bending stiffness term involved in the electromechanical governing equations is explicitly corrected. Through comparisons of predicted power output with two-dimensional finite element analysis, the results show that the present model can better predict the power output performance compared with the traditional model. It is found that the relative corrections to traditional model have nothing to do with the absolute dimensions of the harvesters, but only relate to three dimensionless parameters, i.e., the ratio of the elastic layer’s to the piezoelectric layer’s thickness; the ratio of the elastic modulus of the elastic layer to the piezoelectric layer; and the piezoelectric materials’ electromechanical coupling coefficient squared, k312. It is also found that the upper-limit relative corrections are only related to k312, i.e., the higher k312 is, the larger the upper-limit relative corrections will be. For a PZT-5 unimorph harvester, the relative corrections of bending stiffness and corresponding resonant frequency are up to 17.8% and 8.5%, respectively. An inverse problem to identify the material parameters based on experimentally obtained power output performance is also investigated. The results show that the accuracy of material parameters identification is improved when considering a non-uniform electric field.

A 450-nm blue laser may be suitable to treat benign prostate hyperplasia (BPH) due to its haemoglobin absorption characteristic. The present study compared a novel high-power 450-nm semiconductor blue laser with other lasers marketed for in vitro soft tissue ablation, to evaluate the safety and efficacy of the 450-nm laser in BPH surgery. With the in vitro tissues on an experimental platform in water, the vaporization efficiency and coagulation layer thickness of the novel 450-nm laser and commercially available 532-nm, 980-nm, and 1470-nm lasers were measured at the same power (120 W). The damage to the adjacent tissue and the working noise were also measured. The vaporization efficiency was proved to be 450-nm laser > 532-nm laser > 1470-nm laser > 980-nm laser. Comparison of coagulation layer thickness was as follow: 980-nm laser > 1470-nm laser > 532-nm laser > 450-nm laser. The degree of tissue damage caused by the 450-nm and 532-nm lasers increased with the decrease in distance and increase in time (these are safe when a sufficient distance and short irradiation time are maintained). The heating ability of 980-nm and 1470-nm lasers was much greater than that of 450-nm and 532-nm lasers. The working noise was lower in 450-nm and 1470-nm lasers. The novel 450-nm laser has the advantages of highly efficient tissue vaporization, creating a thin coagulation layer, and low working noise. These characteristics suggest that the novel 450-nm laser may be a promising choice for the surgical treatment of BPH.

Ample evidence has recognized the importance of teacher support for children’s mental health. However, less is known about the factors that may play a role in the association between teacher support and children’s mental health. In the present study, we examined the mediating role of self-concept and the moderating role of area (i.e., rural vs. urban area) in the relationship between teacher support and children’s mental health (i.e., depression and anxiety). We used a sample of Chinese elementary students who enrolled in grades 3 to 6 (N = 525, aged 8–13, 44.54% girls). Results showed that children who perceived more teacher support tended to report better mental health. Moreover, the relationship between perceived teacher support and mental health was mediated by each domain of self-concept. Lastly, the association between teacher support and mental health was moderated by area, with a stronger effect found for urban children compared with rural children. These findings highlight the importance of considering both individual and contextual factors in the association between teacher support and children’s mental health. Practical strategies are proposed for school teachers, professionals, and policymakers to foster children’s psychological well-being.

Prior research demonstrates that understanding of theory of mind develops at different paces in children raised in different cultures. Are these differences simply differences in timing, or do they represent different patterns of cultural learning? That is, to what extent are sequences of theory-of-mind understanding universal, and to what extent are they culture-specific? We addressed these questions by using a theory-of-mind scale to examine performance of 140 Chinese children living in Beijing and to compare their performance with that of 135 English-speaking children living in the United States and Australia. Results reveal a common sequence of understanding, as well as sociocultural differences in children's developing theories of mind.

Anthocyanins, a group of flavonoids, are widely present in plants and determine the colors of the peels of stems, fruits, and flowers. In this study, we used UHPLC-ESI-MS to identify anthocyanins in the herbal plant Dendrobium officinale, which has been used for centuries in China. The results indicated that the total anthocyanin content in samples from Guangxi was the highest. Seven anthocyanins were identified, and the fragmentation pathways were proposed from D. officinale. Most of the identified anthocyanins were composed of cyanidin and sinapoyl groups. We also carried out that the sinapoyl group had active sites on breast cancer receptors by using Schrödinger. The relative levels of the 7 anthocyanins in the samples from the three locations were determined. Transcriptomic analysis was used to analyze the sinapoyl anthocyanin synthesis-related genes in plants, such as genes encoding UGTs and serine carboxypeptidase. We speculated that sinapoyl anthocyanin biosynthesis was associated with the activities of certain enzymes, including chalcone flavonone isomerase-like, hydroxycinnamoyltransferase 1, UGT-83A1, UGT-88B1 isoform X1, serine carboxypeptidase-like 18 isoform X3, and serine carboxypeptidase-like 18.

To solve the problem of low efficiency and poor effect of the current tone mapping methods for the high dynamic range images, the authors propose a hierarchical tone mapping algorithm based on colour appearance model. The discrete Gaussian kernel is used to speed up the bilateral filter. The operation of tone compression in RGB colour space is adopted to correct the colour casts. The extreme values of the pixels are also adjusted in the detail layer. Moreover, after the tone mapping, the colour saturation is enhanced in the image regions of rich details and sharp edges. Experimental results show that the proposed algorithm with less computational cost reduces the halo effect significantly, and achieves the natural colour and the rich details. It outperforms the state-of-the-art methods in terms of visual quality and objective indicators.

The temperature biases of 28 CMIP5 AGCMs are evaluated over the Tibetan Plateau（TP） for the period 1979–2005. The results demonstrate that the majority of CMIP5 models underestimate annual and seasonal mean surface 2-m air temperatures(Tas) over the TP. In addition, the ensemble of the 28 AGCMs and half of the individual models underestimate annual mean skin temperatures（Ts） over the TP. The cold biases are larger in Tas than in Ts, and are larger over the western TP. By decomposing the Ts bias using the surface energy budget equation, we investigate the contributions to the cold surface temperature bias on the TP from various factors, including the surface albedo-induced bias, surface cloud radiative forcing, clear-sky shortwave radiation, clear-sky downward longwave radiation, surface sensible heat flux, latent heat flux,and heat storage. The results show a suite of physically interlinked processes contributing to the cold surface temperature bias.Strong negative surface albedo-induced bias associated with excessive snow cover and the surface heat fluxes are highly anticorrelated, and the cancelling out of these two terms leads to a relatively weak contribution to the cold bias. Smaller surface turbulent fluxes lead to colder lower-tropospheric temperature and lower water vapor content, which in turn cause negative clear-sky downward longwave radiation and cold bias. The results suggest that improvements in the parameterization of the area of snow cover, as well as the boundary layer, and hence surface turbulent fluxes, may help to reduce the cold bias over the TP in the models.

Understanding others’ thoughts and feelings is a social-cognitive capacity known as the theory of mind (ToM). Previous studies have attempted to explore children’s ToM from a specific domain (personal or moral) while lacking comprehensive evidence across domains. Based on the social domain theory, the present study is the first in our knowledge to explore the developmental characteristics of the ToM within different domains of left-behind preschoolers in rural China. This study used a mixed experimental design of 3 (age groups: 4-, 5-, 6-year-old) × 2 (left-behind status: left-behind, non-left-behind) × 3 (domain types: moral, conventional, personal) with 231 rural children aged 4–6 years, combined with a story–question approach to explore the developmental characteristics of their ToM in moral, conventional, and personal domains through tasks, such as rule awareness and false beliefs. The results showed significant main effects of age group, left-behind status, and domain type. Moreover, the interaction effect of age group and domain type was significant. The following conclusions were obtained: (1) The developmental level of the ToM in moral, conventional, and personal domains of rural preschoolers increased with age and the older preschoolers had a more accurate and comprehensive understanding of the ToM in each domain; (2) The experience of being left behind was detrimental to the development of preschoolers’ ToM in each domain; (3) There were differences in children’s development in the moral-, conventional-, and personal-related ToM tasks, with the personal domain ToM developing more slowly; (4) The younger preschoolers showed a clear differentiation between the domains of ToM, with a higher level of development in domains of morality and convention. As preschoolers get older, their performance in the domains becomes more comparable.