Layered rocks exhibit notable transverse isotropy and have a significant impact on the deformation and failure characteristics of underground structures. To a large extent, the mechanical properties of layered rocks are related to the structure and stress state of their bedding planes. To obtain an in‐depth understanding of the deformation and yield characteristics of layered rocks, a mechanical model for layered rocks incorporating planes of weakness and volumetric stress is proposed by improving the strain‐hardening/softening ubiquitous‐joint model based on continuum mechanics methods. In this mechanical model, elastoplastic equations for the matrix and bedding planes of layered rocks are established. The evolution of the mechanical parameters of the matrix and bedding planes of layered rocks with the internal variable is determined. In addition, the sensitivity of the model parameters is analyzed, and a method for determining the parameters is provided to reduce the complexity in obtaining these parameters. The numerical calculation results for the laboratory tests on layered sandstone specimens under various stress levels agree relatively well with the test results, thereby validating the effectiveness of the improved model. The methods and results of this study provide a significant reference for the analysis of the deformation and failure of other layered rocks.
Background Village clinic doctors (VCDs) are part of the health service force in rural China. VCDs’ job satisfaction (JS) is important to the stability of the three-tiered health service system. Since 2009, the Chinese government launched a new health care system reform (NHCSR) which affected VCDs significantly. This study aimed to analysing the effect of NHCSR on JS among VCDs. Methods All the data came from three surveys in Shandong Province conducted in 2012, 2015 and 2018. In 2012, an originally designed questionnaire was used to conduct a baseline survey of 405 VCDs from 27 townships in nine counties. In 2015 and 2018, 519 and 223 VCDs in the same counties were surveyed with the same questionnaire. Descriptive analysis and ANOVA were used to analyse the level and changes in VCDs’ JS. Results The mean scores of VCDs’ total JS were 2.664 ± 1.069, 3.121 ± 0.931 and 2.676 ± 1.044 in 2012, 2015 and 2018, respectively, with a significant difference (F = 28.732, P < 0.001). The mean scores of the medical practice environment and the job itself showed a continuous downward trend. The trends of the mean scores for job reward, internal work environment and organizational management were consistent with the trend for total JS. Conclusion The NHCSR had a partly negative impact on VCDs’ JS. Policy-makers should pay more attention to VCDs’ job reward and medical practice environment. With the implementation of new reform policies, VCDs’ JS should be the subject of more systematic and detailed research.
The mechanical properties of mortar materials in construction are influenced both by their own proportions and external loads. The trend of the stress–strain curve in cracks compaction stage has great influence on the relationship between the strength and deformation of cement mortar. Uniaxial compression tests of mortar specimens with different cement–sand ratios and loading rates were carried out, and the stored and dissipated energies were calculated. Results indicated that the elastic modulus and strength of mortar specimens increase with the cement–sand ratio and loading rate. The energy dissipation shows good consistency with the damage evolution. When the loading rate is less than 1.0 mm/min, most of the constitutive energy at the peak point is stored in the specimen and it increase with cement–sand ratio. A simple representation method of axial stress in cracks compaction stage was proposed and an energy-based damage constitutive model—which can describe well the whole process of cement mortar under uniaxial compression—was developed and verified.
Background General practitioners are the gatekeepers of the health of the residents. This study aims to evaluate the trend and equity of general practitioners' allocation from 2012 to 2017 in China and provide a reference for regional health planning and rational distribution of general practitioners. Methods We extracted the data of general practitioners from 22 provinces, 5 autonomous regions, and 4 municipalities of mainland China. The population and geographical area were taken from the China Statistical Yearbook. The general practitioners' data were taken from the China Health Statistical Yearbook. Lorenz curve, Gini coefficient, and agglomeration degree were used to analyze the data. Results The number of general practitioners was 252,717 in 2017, which equates to 1.82 per 10,000 residents, and accounts for 7.45% of the total number of practicing (assistant) doctors. From 2012 to 2017, the population-based Gini coefficient for general practitioners reduced from 0.31 to 0.24, while the geographical area-based Gini coefficient remained unchanged at 0.73. The agglomeration degree based on population increased from 0.72 to 0.73 in the western region including Tibet (0.403) and Shaanxi (0.513). Moreover, in the eastern region the agglomeration degree reduced from 1.477 to 1.329. In the middle region it rose from 0.646 to 0.802. The agglomeration degree based on the geographical area in the western region increased from 0.270 to 0.277 while the values in Tibet, Qinghai, Xinjiang were less than 0.1. In the eastern region, it reduced from 1.447 to 1.329. It increased from 1.149 to 1.423 in the middle region. Conclusions The number of general practitioners has increased significantly in China. It has a fair allocation based on population. However, the equity based on geographical area is low and uneven in different regions with large regional differences. In the western region, there is an allocation shortage with respect to population and geographical area. Concerned departments should establish and improve the incentive and performance appraisal mechanisms of general practitioners. The Internet + should be used to empower their service capacity and efficiency. The educational input should be increased for the western region and government should encourage the eastern region to support the western region.
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