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Urban parks can mitigate the urban heat island (UHI) and effectively improve the urban microclimate. In addition, quantifying the park land surface temperature (LST) and its relationship with park characteristics is crucial for guiding park design in practical urban planning. The study’s primary purpose is to investigate the relationship between LST and landscape features in different park categories based on high-resolution data. In this study, we identified the land cover types of 123 parks in Luoyang using WorldView-2 data and selected 26 landscape pattern indicators to quantify the park landscape characteristics. The result shows that the parks can alleviate UHI in most seasons, but some can increase it in winter. While the percentage of bare land, PD, and PAFRAC have a positive impact on LST, AREA_MN has a significant negative impact. However, to deal with the current urban warming trend, a compact, clustered landscape configuration is required. This study provides an understanding of the major factors affecting the mitigation of thermal effects in urban parks (UP) and establishes a practical and feasible urban park renewal method under the idea of climate adaptive design, which provides valuable inspiration for urban park planning and design.

The effect of urbanization on the urban thermal environment (UTE) has attracted increasing research attention because its significant effects on local weather and climate, and serious consequences for people. However, systematic study of the relationship between urbanization and UTE has been undertaken only to a limited extent. Using quantitative thermal remote sensing and multi-buffer ring method and multiple spatial scales method, here we analyze Landsat TM/ETM+ images of Zhengzhou in Central China acquired on four different dates in 2017 to investigate the spatiotemporal variations, trends, and driving force in the land surface temperature (LST). Our results showed that LST generally increased with urbanization intensity. This trend was extremely obvious in spring and summer, weak in winter, and slightly downward in autumn. Moreover, PLAND (e.g., percentage of impervious surface in a landscape) has the most significant effect on urban LST, and generally increases as the spatial scale becomes larger. In conclusion, the study recommends that urban planning in Zhengzhou should prioritize PLAND, especially at large spatial scales. These results provide a scientific reference for urban planners who are committed to the sustainable development of Zhengzhou City.

Epoxy resins are employed in many engineering applications in which mechanical properties at different strain rates and temperatures must be quantified for effective use. It is known that these properties are related through the principle of time-temperature equivalence. In this paper, the application of this equivalence is explored in detail, at both small and large strains, and used as part of a strategy for calibrating a constitutive model that can reproduce the stress-strain behaviour in different mechanical conditions. In order to achieve this, quasi-static compression experiments were performed at temperatures from -40 to +40 °C in a screw-driven load frame; room temperature rate dependent experiments were performed from 0.0005 to 6300 s-1 using a screw-driven load frame, hydraulic compression system and Split Hopkinson Pressure Bar apparatus. Dynamic mechanical analysis and differential scanning calorimetry were also performed. A three-network (TN) polymer model was fit to the mechanical behaviour up to a strain of 0.5. This model, combined with time-temperature based mappings gave a good understanding of the thermomechanical behaviour of the material, and also demonstrates an approach that can be used for a wide range of polymers.

Tensile tests are often used as part of material characterisation strategies; however, the observed deformation is often complex, and it can be difficult to distinguish the underlying material behaviour from the structural response of the specimen. The objective of the research in this paper was to investigate whether a more accurate calibration of a material model could be obtained by considering not just the global behaviour of the specimen, but also the local strain-time response calculated from full-field displacement information obtained using digital image correlation. Tensile experiments were performed using ISO standard, flat, dog bone specimens. Optical and infra-red imaging were used to calculate full field displacement and temperature maps, and a finite element model of the experiment was produced. These were combined with compression test data from the same material to calibrate a constitutive model, which was shown to describe well the deformation and temperature rise in the specimen. The research demonstrates that it is insufficient to use force-displacement information from tensile experiments to calibrate, or validate, constitutive models of polymers. Further, it demonstrates a more applicable method, which could be further automated in the future.

Urban green spaces play a crucial role in maintaining urban ecosystem sustainability by providing numerous ecosystem services. How to quantify and evaluate the ecological benefits and services of urban green spaces remains a hot topic currently, while the evaluation is barely applied or implemented in urban design and planning. In this study, super-high-resolution aerial images were used to acquire the spatial distribution of urban green spaces, a modified pre-stratified random sampling method was applied to obtain the vegetation information of the four types of urban green spaces in Luohe, a common plain city in China, and i-Tree Eco model was further used to assess the vegetation structure and various ecosystem services including air quality improvement, rainfall interception, carbon storage, and sequestration provided by four types of urban green spaces. The modeling results reveal that there were about 1,006,251 trees in this area. In 2013, all the trees in these green spaces could store about 54,329 t of carbon, sequester about 4973 t of gross carbon, remove 92 t of air pollutants, and avoid 122,637 m&sup3, of runoff. The study illustrates an innovative method to reveal different types of urban green spaces with distinct ecosystem service productivity capacity to better understand their various roles in regulating the urban environment. The results could be used to assist urban planners and policymakers to optimize urban green space structure and composition to maximize ecosystem services provision.

Urban ecosystem dysfunction, habitat fragmentation, and biodiversity loss caused by rapid urbanization have threatened sustainable urban development. Urban habitat quality is one of the important indicators for assessing the urban ecological environment. Therefore, it is of great practical significance to carry out a study on the driving mechanism of urban habitat quality and integrate the results into urban planning. In this study, taking Zhengzhou, China, as an example, the InVEST model was used to analyze the spatial differentiation characteristics of urban habitat quality and Geodetector software was adopted to explore the driving mechanism of habitat quality at different grid-scales. The results show the following: (1) LUCC, altitude, slope, surface roughness, relief amplitude, population, nighttime light, and NDVI are the dominant factors affecting the spatial differentiation of habitat quality. Among them, the impacts of slope, surface roughness, population, nighttime light, and NDVI on habitat quality are highly sensitive to varying grid-scales. At the grid-scale of 1000 to 1250 m, the impacts of the dominant factors on habitat quality is closer to the mean level of multiple scales. (2) The impact of each factor on the spatial distribution of habitat quality is different, and the difference between most factors has always been significant regardless of the variation of grid-scales. The superimposed impact of two factors on the spatial distribution of habitat quality is greater than the impact of the single factor. (3) Combined with the research results and the local conditions of Zhengzhou, we put forward some directions of habitat protection around adjusting urban land use structure, applying nature-based solutions and establishing a systematic thinking model for multi-level urban habitat sustainability.

Extended finite element method (XFEM) is introduced in this study, and the normal direction of fracture surface under different failure modes is determined, which provides a new and efficient technology for failure prediction of composite laminates. According to the failure criterion, a user-defined FORTRAN subroutine (UDMGINI) has been written for Abaqus/Standard solver to model the damage initiation and crack propagation of G23 out-of-plane shear test. By comparing the load–displacement curve, strain field and failure mode of experiment, FEM and XFEM, XFEM can effectively predict the crack initiation and propagation. Meanwhile, the crack path of matrix failure simulated by XFEM is smooth without bifurcation, which is more consistent with experimental result. Moreover, by comparing damage factors of specimen before damage initiation in G23 test, it is found that the matrix tensile failure occurs more easily than matrix compressive failure at the root of V-notch, where cracks are the first to initiate.

While green roofs have been deemed promising in mitigating environmental issues caused by rapid urban development, city-scale green roof studies have faced various obstacles, especially difficulties in obtaining accurate data for analysis. This study developed a new, cost-effective approach to assessing green roof development potential by using ultra-high-resolution (UHR) (0.09 m) Unmanned Aerial Vehicle (UAV) imagery in a case study site (Central Luohe with an area of 158 km2) in China. Specifically, the data was processed, interpreted, and classified to create highly accurate land-use and building roof spatial resources databases. A decision-making flowchart was developed for preliminary determination of a building stock’s suitability for green roof implementation and the preferred type based on the five influencing factors and building roof classification. Subsequently, a two-stage strategy for large-scale green roof development was proposed. The approach demonstrated in this research greatly improves the accuracy of city-scale studies on roof spatial resources and enables better planning and development of urban green spaces at the local level.

Polymers are widely used for lightweight design in industrial applications, such as helmets and car bumpers, where the most common causes of failure or damage are dynamic impact events. It is well known that the mechanical response of most polymers is highly dependent on the loading rate and temperature, and that it is not sufficient to use properties measured under static loads in the analysis of dynamic events. However, the time-temperature equivalence phenomenon offers the chance to predict high-rate performance using low-rate data. In this study, information about the constitutive behaviour of two different molecular weight polycarbonates, is obtained in low-rate experiments and then compared with the high-rate response. A master curve of storage modulus constructed from Dynamic Mechanical Analysis data is employed to understand the viscoelastic response under small-strain loading at various frequencies and temperatures. For the large-strain constitutive response, experiments at strain rates from 0.001 s-1 to 3000 s-1 are performed using a conventional crosshead device, hydraulic device, and split-Hopkinson pressure bar. Moreover, experiments at strain rates of 0.01 s-1 and temperatures from -60 to 120 °C are also performed, and the results are compared. This approach can distinguish ’constitutive’ rate dependence from the effects of specimen self-heating due to adiabatic heating under high-rate deformation. Meanwhile, the molecular weight effects on the mechanical response at varying rates and temperatures are also noted.

Rapidly growing cities often struggle with insufficient green space, although information on when and where more green space is needed can be difficult to collect. Big data on the density of individuals in cities collected from mobile phones can estimate the usage intensity of urban green space. Taking Zhengzhou&rsquo, s central city as an example, we combine the real-time human movement data provided by the Baidu Heat Map, which indicates the density of mobile phones, with vector overlays of different kinds of green space. We used the geographically weighted regression (GWR) method to estimate differentials in green space usage between weekdays and weekends, utilizing the location and the density of the aggregation of people with powered-up mobile phones. Compared with weekends, the aggregation of people in urban green spaces on workdays tends to vary more in time and be more concentrated in space, while the highest usage is more stable on weekends. More importantly, the percentage of weekday green space utilization is higher in small parks and green strips in the city, with the density increasing in those small areas, while the green space at a greater distance to the city center is underutilized. This study validates the potential of applying Baidu Heat Map data to provide a dynamic perspective of green space use, and highlights the need for more green space in city centers.

In this paper, the complex failure modes including intra-laminar matrix cracking , inter-laminar delamination and their interaction such as matrix cracking induced delamination and delamination kinking of curved composite laminates with free edge effect are investigated with both experimental testing and three-dimensional numerical modeling . Four-point bending testing of curved composite laminates with designed stacking sequences illustrated the different failure modes, and the experimental results are used to validate the proposed three-dimensional (3D) numerical model with zero-thickness cohesive elements and a mixed-mode traction-separation damage law. It is demonstrated that the proposed 3D modeling can successfully predict the stacking sequence dependent failure modes and locations, as well as crack initiation and propagation sequence, and the failure loads of the curved composite laminates. The advantage of the 3D modeling is further explored and attributed to the ability to predict the complex 3D stress distribution including the free edge effect and the progressive damage accumulation within the critical section of the curved composite laminates.