Class-Guidance Network Based on the Pyramid Vision Transformer for Efficient Semantic Segmentation of High-Resolution Remote Sensing Images

Small differences between classes and big variations within classes in multicategory semantic segmentation are problems that are not completely solved by the “encoder–decoder” structure of the fully convolutional neural network, leading to the imprecise perception of easily confused categories. To address this issue, in this article, we believe that sufficient contextual information can provide more interpretation clues to the model. Additionally, if we can mine the class-specific perceptual information for each semantic class, we can enhance the information belonging to the corresponding class in the decoding process. Therefore, we propose the class-guidance network based on the pyramid vision transformer (PVT). In detail, with the PVT as the encoder network, the following decoding process is composed of three stages. First, we design a receptive field block to expand the receptive field to different degrees using parallel branching processing and different dilatation rates. Second, we put forward a semantic guidance block to utilize the high-level features to guide the channel enhancement of low-level features. Third, we propose the class guidance block to achieve the class-aware guidance of adjacent features and achieve the refined segmentation by a progressive approach. The overall accuracy of the method is 88.91% and 88.87%, respectively, according to experimental findings on the Potsdam and Vaihingen datasets

Exploring Equity in Healthcare Services: Spatial Accessibility Changes during Subway Expansion

The unequal allocation of healthcare resources raises many fundamental problems, one of which is how to address inequity in population health. This paper focuses on disparities in public transport healthcare accessibility, with a special focus on an expanding subway system. Based on a vulnerability index, including factors that are likely to limit healthcare opportunities, a two-step floating catchment area method was used to assess the distribution of supply and demand for healthcare. Quantity, quality, and walking distance accessibility were aggregated into hexagonal grids. The Theil index was used to measure inequity and understand the influence of subways on spatial disparities in healthcare accessibility. The ongoing construction of the subway has heterogeneous impacts on healthcare accessibility for different parts of the city and exacerbates spatial inequity in many areas. In an environment where people in peri-urban areas are excluded from healthcare access because of low subway coverage, the results suggest that the potential for subways to address inaccessibility is limited. The findings highlight the requirement of efficient public transport services and are relevant to researchers, planners, and policymakers aiming to improve accessibility to healthcare, especially for populations who dwell in winter cities

Mechanical Performance of Eco-Friendly Sandwich Wall with Rice Husk Recycled Concrete

In the construction industry, an approach to alleviate the environmental problem is to apply ecological composite materials to the construction field. In this paper, the authors added the recycled aggregate and the rice husks to the concrete and measured the strengths of rich husk recycled concrete (RHRC) with different factors as well as determined the constitutive model. Subsequently, the flexural experiment of RHRC sandwich wall was carried out and analyzed in detail, which proved that it could bear the wind loads in normal use condition by the calculation of the experimental data. Then, the compressive experiment and analyses were conducted similarly. Moreover, the finite element method was applied to study the influence of tie bars on the flexural bearing capacity and to deduce the simplified calculation method of vertical bearing capacity of RHRC walls

Exploring Equity in a Hierarchical Medical Treatment System: A Focus on Determinants of Spatial Accessibility

It is essential to understand the spatial equity of healthcare services to achieve the Sustainable Development Goals. Spatial and non-spatial factors affect access to healthcare, resulting in inequality in the hierarchical medical treatment system. Thus, to provide a comprehensive equity evaluation, it is indispensable to investigate the extent to which spatial accessibility to healthcare services varies due to various factors. This study attempted to analyze the determinants of healthcare accessibility under multi-trip modes and integrate them into Theil index, as a demand index to evaluate spatial equity in the system. The results reveal an inadequate and inequitable distribution of healthcare resources. While access to primary hospitals is limited (47.37% of residential locations cannot access them on foot), 96.58% of residential locations can access general and tertiary hospitals via public transport or driving. Furthermore, inequitable access to the three-tiered medical system was evaluated on a more granular scale, with primary hospitals being closest to achieving equity (inequitable for only 48.83% of residential locations), followed by general and tertiary hospitals (82.01% and 89.20%, respectively). The unequal residential locations brought on by an abundance of medical resources are far from those with a shortage of resources (66.86% > 5.34%). It is thus suggested that services be expanded or resources be transferred to move toward a more equitable system. Our findings provide policymakers with insights into how to increase accessibility to public health

Multiobjective Optimization of Tool Geometric Parameters Using Genetic Algorithm

Tool geometric parameters have a huge impact on tool wear. Up to now, there are only a few researches on tool geometric parameters and optimization, and the single objective function of parameter optimization used by researchers during high-speed machining (HSM) mainly is the minimum cutting force. However, the elevated cutting temperature also greatly affects tool wear due to the numerous cutting heat generation. Thus, to reduce tool wear, it is the most fundamental approach to taking into account the comprehensive control of the cutting force and cutting temperature because they are the two most important physical quantities in metal cutting processes. This work proposes a new optimization idea of the cutting-tool’s multi geometric parameters (three main parameters: rake angle, clearance angle, and cutting edge radius) with two objective functions (the cutting force and the temperature). Based on the response surface method (RSM), we have established the modified functional relation models of the influence of tool geometric parameters on the cutting force and temperature according to the finite element simulation results in high-speed cutting of Ti6Al4V. Then the models are solved by using a genetic algorithm, and the optimal tool geometric parameters values that can concurrently control the two objectives in their minimum values are obtained. The advantages lie in the strategy of the separate models of the cutting force and cutting temperature owing to their different dimensions and the solution of the models through giving the cutting force and cutting temperature different weight coefficients. The optimal results are verified by experiments, which shows that the optimal tool geometric parameters are very effective and vital for ensuring both the cutting force and the cutting temperature not too high. This work is of great significance to the cutting tool design theory and its manufacturing for reducing tool wear

The Influence of Bit Edge Shape Parameters on Bone Drilling Force Based on Finite Element Analysis

Bone drilling is a common surgery procedure. The drill bit shape directly affects the drilling force. Excessive drilling force may cause bone damage. In this work, on the premise of analyzing and comparing several finite element method (FEM) simulation results for drill bit of 5 mm in diameter commonly used in medical practice, a combination of drilling speed and feed rates which can minimize the drilling force for drilling parameters is determined. Then, the effects of the drill bit shape parameters including helix angle, point angle and edge radius on the drilling force are simulated by using the obtained drilling parameters, and after validation the FEM analysis results show that their variation trend is the same as the experimental one. Then, the optimum bit structure parameters are obtained through the following research: (1) the prediction model of the relationship between drill edge parameters and drilling force is established based on the result of FEM of the drilling process; (2) A particle swarm optimization algorithm is used to obtain the optimal matching parameters of the bit structure; (3) The priority order of the influence of the parameters of the bit on the drilling force is analyzed. The results show that the order of the influence is: the edge radius is the largest, the point angle is the second, and the helix angle is the smallest. The optimum combination of bit structure is that point angle, helix angle and edge radius are 95°, 35°, and 0.02 mm, respectively

Bond Behavior of Reinforced Concrete Considering Freeze–Thaw Cycles and Corrosion of Stirrups

In relatively cold environments, the combination of freeze–thaw and steel bar corrosion is a key factor affecting the durability of concrete. The adjustment of the stirrup ratio would change the mechanical performance of surrounding concrete, while the circumferential compressive stress can further improve the bonding performance. Hence, based on eccentrically tensioned specimens, the influence of corrosion of stirrups and freeze–thaw of concrete on bond properties is discussed in this paper. The monotonic pull-out test of reinforced concrete specimens is carried out to study the variation rules of bond strength and slip between steel bar and concrete under the coupling action of corrosion rate, freeze–thaw times and stirrup spacing. Based on the experimental data, the empirical formula for the ultimate bond strength is obtained, and a bond–slip constitutive model is established considering the stirrup spacing, stirrup corrosion rate and freeze–thaw times. Then, a refined finite element pull-out specimen model is established by ABAQUS simulation, and the numerical simulation results are compared with the real test ones, so as to make up for the deficiencies in the test and lay the foundation for further finite element analysis

Mechanical Performance Analysis and Parametric Study of a Self-Anchored Suspension Bridge with Ultra-Wide Double-Sided Steel Box Girder

A sufficient understanding of mechanical performance of self-anchored suspension bridge with double-sided steel box girder is essential for design and normal use as such bridges are widely built in urban bridge. Using the Yunlongwan Bridge which is a suspension bridge with ultra-wide double-sided steel box girder as an example, this paper investigates its deformation and mechanical performance under vehicle load. Firstly, based on the field test results, the deformation performance of the bridge and the stress distribution of the main girder are analysed, with emphasis on the shear lag effect of double-sided steel box girder. Then, a multiscale model of the bridge was built, and the accuracy of the model was verified by comparison with the test data. Finally, the influence of design parameters on the mechanical behaviour of double-sided steel box girder is studied by numerical simulation. The results show that the deformation of the bridge has good symmetry, there is obvious shear lag effect on the main girder, and the U-rib thickness, diaphragm spacing, and vehicle load could significantly affect the stress of the main girder top plate. The obtained analytical results lead to a better understanding of the mechanical performance and provide reference for the design of self-anchored suspension bridge with double-sided steel box girder

Influences of Multilayer Graphene and Boron Decoration on the Structure and Combustion Heat of Al3Mg2 Alloy

To improve the engine-driven performance of propellants, high-energy alloys such as Al and Mg are usually adopted as annexing agents. However, there is still room for improvement in the potential full utilization of alloy energy. In this study, we investigated how to improve combustion efficiency by decorating Al3Mg2 alloy with multilayer graphene and amorphous boron. Scanning electron microscopy and Raman tests showed that decorating with multilayer graphene and amorphous boron promoted the dispersion of Al3Mg2 alloy. The results showed that decorating with 1% boron and 2% multilayer graphene improved the combustion heat of Al3Mg2 alloy to 32.8 and 30.5 MJ/kg, respectively. The coexistence of two phases improved the combustion efficiency of the matrix Al3Mg2 alloy