In order to reduce the number of transverse joints and improve the cracking resistance of Portland cement concrete pavement, a series of diagonally arranged prestressed tendons are applied in the pavement slab, defined as cross-tensioned concrete pavement (CTCP). However, the reduction in the number of transverse joints causes additional stresses and deformations within the CTCP slab which cannot be addressed by only increasing the level of prestress applied to the slab. It is necessary to lay a well-designed sliding layer between the base and the CTCP slab to reduce the stresses and deformations. The influence of coefficient of friction (COF) of a sliding layer on the CTCP structure was studied using both finite element analysis and analytical solutions. Results show that the sliding layer with a smaller initial (before final post-tensioning) COF can reduce the stresses caused by wheel and thermal load while maintaining the prestress in the CTCP slab. Larger long-term (after final post-tensioning) COF of the sliding layer can minimise the CTCP slab end movements. However, the long-term COF should not be larger than 1.04. In addition, a coefficient of friction tester for the CTCP sliding layer was designed and developed based on the Amonton law. Optimum structure parameters and type of the CTCP sliding layer were obtained using "Sand + Polyethylene-plastic Sheeting" as a sliding layer. The optimum cement content of the "Sand + Cement + Polyethylene-plastic Sheeting" sliding layer was also determined from the experimental results.
Introduction: Pregnancy and childbirth are highly challenging, as it is an event of significant psychological, social and emotional change for women that may predispose them to stress and anxiety. Music therapy is emerging with increasing popularity as an additional treatment for ameliorating stress, anxiety and labor pain. This study aimed to examine the effect of music interventions on maternal perinatal mental health and childbirth outcomes to establish comprehensive evidence for clinical decision-making. Methods: This study is a systematic review and meta-analysis. Results: Twenty-six randomized controlled trials (RCTs) involving 3,969 women included in this review. The overall effects indicated that anxiety levels in women in the music group were significantly lower than in the usual care group (SMD =-4.17, 95% CI:-5.13 to-3.20). The pooled results also indicate that music interventions could significantly reduce depressive symptoms (SMD =-2.66, 95% CI:-4.98 to-0.34). The music interventions also tended to reduce women's stress, but without significantly statistical differences (Z=1.84, P=0.07). Eight studies reported the effects of music interventions on the physical outcomes of pain and blood pressure and pain. Music interventions could significantly reduce pain intensity (SMD =-1.43, 95% CI:-2.67 to-0.18, blood pressure: systolic BP (SMD =-2.23, 95% CI:-3.76 to-0.70), and diastolic BP (SMD =-1.80, 95% CI:-3.00 to-0.61), and reduced heart rate vital signs (SMD =-3.33, 95% CI:-4.36 to-2.30). Five studies reported the effects of music interventions on women's satisfaction and quality of life, and found that music interventions significantly improved these outcomes (SMD =2.86, 95% CI: 1.66 to 4.05). In terms of child outcomes, the music interventions positively stimulated fetal movement (SMD =1.62, 95% CI: 0.05 to 3.19) and accelerations (SMD =1.08, 95% CI: 0.74 to 1.42). Conclusions: These results suggest that music interventions may have the potential to reduce obstetrical complications, so that application of music interventions across all three trimesters and during labor may be advisable in routine obstetric practice.
The purpose of this paper is to explore the current state of China's logistics development and the future development. In order to fulfill the research objective, a literature-based survey and content analysis is used to investigate the development level of China's logistics research, also, secondhand data based statistical analysis is used as the main method to study the development of Chinese logistics in this paper. While every effort has been made to ensure that the most up-to-date data is available in the analysis, this is not always possible due to the obvious reasons for data scarcity and data integrity. Despite the improvements and progress made by the government and other agencies, the current logistics infrastructure, especially the transportation network, customs procedures and warehousing facilities are still lacking. Future developments are also highlighted to portray an accurate assessment of China's logistics situation. This is the latest comprehensive research on the development of China's logistics in the known scope. It provides an opportunity for companies that want to enter the Chinese market to understand the development of China's logistics.
What is already known on this topic? The average secondhand smoke exposure rate was 68.1% in China in 2018. The World Health Organization suggests that legislation must be used to achieve a 100% smoke-free environment and protect nonsmokers from secondhand smoke. What is added by this report? This study showed that the implementation of the Amendment Regulations on Smoking Control in Public Places of Shanghai had a significant effect on reducing the exposure rate of secondhand smoke. The rate in 2018 was 46.7%, which was significantly lower than that (58.5%) before implementation in 2016. What are the implications for public health practice? Considering the high exposure and the harm of secondhand smoke in China, it is necessary to promote smoke-free legislation and enforce tobacco control measures.
Exact settlement measurement of substructures plays an important role in their status detection throughout all-life-cycle of high-speed railway. A Hydrostatic Pressure Difference Levelling system (HPDL) is developed based on the mechanism that pressures of any two points at different elevations in incompressible static liquid are different. The approach accounts for a hyperbolic variation in the density of the pressure transmission liquid with temperature, variation in the earth’s gravitational field and the elevation at the measurement point. High accuracy capacitive differential pressure transmitters are adopted owing to their high sensitivity, temperature-insensitive, low energy consumption, and sensing stability. The HPDL results are verified with settlement values measured by the precise level. It was demonstrated that the HPDL results correlate well with the precise level and can be considered as an effective method to measure the settlement of high-speed railway substructures.
Sliding layer is an important component of cross-tensioned prestressed concrete pavement, friction coefficient of slab bottom is decreased by setting sliding layer, so as to reduce the frictional stress at the bottom of the plate and increase the length of the plate. In order to analyze the effect of "sand + polyethylene film" type sliding layer on friction coefficient, and also recommend the optimal sliding layer parameters, The effect of fineness modulus of sand, thickness of sliding layer and specification of polyethylene film on sliding friction coefficient was discussed through orthogonal test. At the same time, The significance level of sliding layer parameters was assessed on the basis of range analysis. The laboratory test results show that the sliding effect of medium sand is better than that of fine sand and coarse sand, and, the friction coefficient reaches the minimum value with sand layer thickness of 10mm, polyethylene film thickness of 30 m µ , The significance level of sliding layer parameters ranks as follows: fineness modulus of sand > sand thickness > polyethylene film specification, the test results can be provided for calculating reference for friction stress of the cross-tensioned prestressed concrete pavement..
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