Scaffold Structural Microenvironmental Cues to Guide Tissue Regeneration in Bone Tissue Applications

In the process of bone regeneration, new bone formation is largely affected by physico-chemical cues in the surrounding microenvironment. Tissue cells reside in a complex scaffold physiological microenvironment. The scaffold should provide certain circumstance full of structural cues to enhance multipotent mesenchymal stem cell (MSC) differentiation, osteoblast growth, extracellular matrix (ECM) deposition, and subsequent new bone formation. This article reviewed advances in fabrication technology that enable the creation of biomaterials with well-defined pore structure and surface topography, which can be sensed by host tissue cells (esp., stem cells) and subsequently determine cell fates during differentiation. Three important cues, including scaffold pore structure (i.e., porosity and pore size), grain size, and surface topography were studied. These findings improve our understanding of how the mechanism scaffold microenvironmental cues guide bone tissue regeneration

Influence of built environment on outdoor thermal comfort: A comparative study of new and old urban blocks in Guangzhou

Urban populations face increasing heat stress in cities. However, the influence of the built environment of new and old urban blocks on pedestrian thermal comfort remains unclear. This study selected typical old (Yongqingfang) and new urban areas (Knowledge City) in Guangzhou, China, as our research sites. Through field monitoring and surveys, we used physiological equivalent temperature (PET) and thermal comfort vote (TCV) to evaluate outdoor thermal comfort by thermal walk experiments. We analyzed the relationships between built environment variables, meteorological variables, and pedestrian thermal comfort at the two sites. Our analysis revealed significant differences in the built environment and meteorological conditions between the new and old urban blocks within the 60-m buffer zone. PET and TCV showed noticeable spatiotemporal variations in both sites, and their correlation was stronger in the morning (r = 0.87–0.89) than late afternoon (r = 0.60–0.70). Our stepwise regression model indicated that sky view factor and building coverage ratio significantly affected outdoor thermal comfort in old and new urban blocks. Built environment variables explained a higher percentage of the variance in PET (Yongqingfang R2: 0.59–0.82, Knowledge City R2: 0.32–0.81) than TCV (Yongqingfang R2: 0.45–0.57, Knowledge City R2: 0.48–0.69). In short, built environment variables affected thermal indices more than thermal perception. The impact of built environment variables on TCV is also greater in new urban areas than in old urban blocks. Our findings provide insights into the complex relationship between built environments and outdoor thermal comfort in different urban landscapes, which informs climate-resilient urban design

Defining Stress Thresholds of Granite Failure Process Based on Acoustic Emission Activity Parameters

In order to study the crack closure stress threshold σcc of hard rock, crack initiation stress threshold σci, stress threshold σcs of crack interaction, and damage stress threshold σc d, uniaxial compression test was carried out on granite samples. Stress sensor and dynamic strain gauge are used to measure the load, longitudinal, and lateral deformation of rock in real time. The acoustic emission characteristic parameters of rock fracture process are obtained by using the acoustic emission system. According to the change rule of the AE event rate, cumulative energy, energy rate, duration, and amplitude in the whole process of granite sample fracture, the stress threshold (σcc, σci, σcs, and σc d) of each loading stage in the process of rock sample fracture is obtained. The relationship between the stress threshold (σcc, σci, σcs, and σc d) of each stage and the uniaxial compressive strength σUCS of rock samples in the whole process of fracture is analyzed, which shows that the deformation characteristics and crack evolution law of the rock are unified. The research results can provide some reference for further understanding of rock damage evolution mechanism in engineering field

Scale Effects on the Calculation of Ecosystem Service Values: A Comparison among Results from Different LULC Datasets

Land use/land cover (LULC) has an important impact on the ecological environment and is crucial for calculating ecosystem service values (ESVs). However, whether and to what extent the ESVs vary when calculated by LULC product data at different spatial scales remain unclear. Data from two LULC products were used in this study, and two datasets with different spatial scales were obtained by resampling. Then, the ESVs were calculated by the equivalent factor method. Finally, the impacts of LULC on ESVs at different scales were studied, revealing the following: (1) The ESVs calculated by LULC products and by the same products at different scales are different. (2) The difference in the ESVs calculated by the two LULC datasets is approximately 28%, and the difference tends to decrease with increasing scale. (3) With an increase in the LULC scale, the overall change trend of ESVs also increases, and the increasing trend gradually moderates. In addition, the ESVs and LULC scale conform to a logarithmic relationship, and the coefficient of determination (R2) is greater than 0.7. These results have important reference value for obtaining reliable ESVs

Spatiotemporal evolution patterns of urban heat island and its relationship with urbanization in Guangdong-Hong Kong-Macao greater bay area of China from 2000 to 2020

The unprecedented wave of urbanization has led to the development of the urban heat island (UHI) effect in the Guangdong-Hong Kong-Macao greater bay area (GBA) of China. In this study, the spatiotemporal evolution patterns of UHI and its relationship with the urban expansion of the GBA from 2000 to 2020 were explored. First, the space–time cube model and emerging hot spot analysis were applied to identify the spatiotemporal patterns of UHIs. Second, centroid movement analysis, spatial coupling analysis, and a geographical detector model were applied to quantify the relationship between UHIs and urban expansion. Results found that urban expansion was strongly influenced and highly coupled with the UHI change in the GBA. The main hot spot patterns, intensifying hot spot, persistent hot spot, and sporadic hot spot were distributed in the GBA center. Importantly, three intensifying hot spot areas were detected at the junctions of several major cities, where the increases in land surface temperature and urban expansion were spatially consistent. It is recommended that urban planning should consider the fragile thermal environment in highly urbanized areas. This study provides a novel spatiotemporal analytical framework for monitoring the long-time series of changes in the surface environment of cities

A Primary Support Design for Deep Shaft Construction Based on the Mechanism of Advanced Sequential Geopressure Release

The construction of 1500 m depth shaft in Xincheng Gold Mine, China, faces complex stress conditions such as high geostress (>50 MPa), high ground temperature (>50 °C), high water-pressure (>9 MPa), and highly corrosive. Traditional deep shafts excavated by the sinking and lining method cannot adapt to high geostress problems, such as rock bursts and large deformations, etc., in the deep shaft construction process. To avoid and adjust the high geostress induced the rockburst and large deformations, the mechanism of the advanced sequential geopressure release (ASGR) has been proposed for the ground control in deep shaft construction. In this paper, the safe distance between the concrete lining and the shaft excavation face is determined based on the ASGR mechanism, which can provide the space for geopressure release, and primary support based on rock mass quality and numerical simulation was employed to control the geopressure and deformation. A new support scheme for the deep shaft is proposed, using long bolts to restrain severe deformations, metal mesh, and a double reinforcement bar to improve the induced stress distribution. According to the results, the construction scheme of deep shaft has been improved, and the safe support distance of the proposed scheme is determined to be 12 m, with an interval of three excavation cycles. Compared to the original scheme of shaft lining after excavation, the proposed scheme based on the ASGR mechanism can effectively improve the geopressure release and benefit from controlling the rockburst and large deformation of deep shaft induced by high geostress conditions. The stress distribution in the lining is more uniform, and safety factor of the lining is increased to 2.0, which is benefit the long-term stability of deep shaft

Design, fabrication, and realisation of a robotic fish actuated by dielectric elastomer with a passive fin

Abstract Robotic fish actuated by smart materials has attracted extensive attention and has been widely used in many applications. In this study, a robotic fish actuated by dielectric elastomer (DE) films is proposed. The tensile behaviours of DE film VHB4905 are studied, and the Ogden constitutive equation is employed to describe the stress‐strain behaviour of the DE film. The fabrication processes of the robotic fish, including pre‐stretching treatment of the DE films, electrode coating with carbon paste, and waterproof treatment, are illustrated in detail. The dynamic response of the fabricated DE actuators under different excitation voltages is tested based on the experimental setup. Experimental results show that the first‐order natural frequencies of the obtained DE actuator in air is 4.05 Hz. Finally, the swimming performances of the proposed robotic fish at different driving levels are demonstrated, and it achieves an average swimming speed of 20.38 mm/s, with a driving voltage of 5kV at 0.8 Hz

Interactive Impacts of Built Environment Factors on Metro Ridership Using GeoDetector: From the Perspective of TOD

TOD (transit-oriented development) is a planning concept that uses public transportation stations as the center of development, and it aims to integrate land use efficiency and transportation planning linkages to encourage the use of public transportation. The impact of metro TOD projects on urban transportation is multifaceted and complex, and the promotion of metro TOD ridership is an important topic in academic circles. However, the theoretical analysis framework of the impact mechanism of metro TOD ridership is still not perfect. Most studies ignore the TOD characteristics of the stations and the interaction between the station area’s land use and the station area functional linkage. Moreover, a few studies have focused on the mechanisms of the impact of TOD built environment factors on the spatial differentiation of station ridership, and the interactive effects of built environment factors. In this paper, the factors of a metro TOD station built environment were selected based on the node–place–linkage model expanded by the 5D principle of TOD, and a solution is provided for the computable transformation of the 5D principle. The GeoDetector method was used to detect the individual and interactive effects of the TOD built environment factors. The results show that the spatial distribution of the metro TOD station area ridership shows a core–peripheral structure and spatial heterogeneity, both on weekdays and weekends. Moreover, the individual effects of each factor can explain up to 49% and 35% of the traffic distribution on weekdays and weekends, respectively. In addition, the two-factor interactive effect has a stronger influence on metro ridership. The interactive effect can explain up to 72% and 77% of the traffic distribution on weekdays and weekends, respectively. Furthermore, the individual effects of each factor exhibited spatial heterogeneity in the local spaces, showing spatial facilitation and inhibition, respectively. Finally, the main policy recommendations are as follows: One of the important ways to guide the development of cities toward polycentric structure is to promote a TOD model in the peripheral areas of the cities. Building more public open spaces in TOD station areas and improving the collection and distribution capacity of the bus transport systems can effectively stimulate the ridership of metro stations

Optimization Drift Support Design Based on Engineering Geological and Geotechnical Analysis in Deep Hard-Rock Mine: A Case Study

Geotechnical issues due to inappropriate support designs of underground drift will affect mining developments and production. The aim of this study was to provide a systematic support design method for deep hard-rock drifts in China. Field investigations and laboratory studies were carried out on the engineering geological properties of the rock masses along drifts in the Sanshandao Gold Mine. Potential wedge analysis and safety factors were determined using Unwedge software. The rock mass properties and support requirements were analyzed accordingly using different rock mass classification systems; then, an updated combined support system including rock bolts, wire mesh, and shotcrete was proposed. Numerical methods were used to quantify the plastic zone and principal stress of the drift, the plastic zone was reduced, and the rock stress state was improved after installing the support systems. Field monitoring data also confirmed that the updated support system prevented excessive rock mass deformation in drift. This study provides a reliable method for deep hard-rock drift support at Sanshandao Gold Mine and will also be helpful for the optimization of subsequent support