Previous work has established the feasibility of producing acrylic denture bases reinforced with layers of highly drawn linear polyethylene fibres in a woven form. This paper reports on the mechanical properties of the system, including the effect of water conditioning. It is confirmed that substantial improvements in impact strength can be obtained by the incorporation of the polyethylene fibres in woven form. The fibre/resin integration within the dentures has also been studied by optical microscopy. It was found that delamination may occur during some processing stages and steps are suggested to avoid this problem.
The study of urban spatial structure is currently one of the most popular research fields in urban geography. This study uses Lanzhou, one of the major cities in Northwest China, as a case area. Using the industry classification of POI data, the nearest-neighbor index, kernel density estimation, and location entropy are adopted to analyze the spatial clustering-discrete distribution characteristics of the overall economic geographical elements of the city center, the spatial distribution characteristics of the various industry elements, and the overall spatial structure characteristics of the city. All of these can provide a scientific reference for the sustainable optimization of urban space. The urban economic geographical elements generally present the distribution trend of center agglomeration. In respect of spatial distribution, the economic geographical elements in the central urban area of Lanzhou have obvious characteristics of central agglomeration. Many industrial elements have large-scale agglomeration centers, which have formed specialized functional areas. There is a clear "central-peripheral" difference distribution in space, with an obvious circular structure. Generally, tertiary industry is distributed in the central area, and secondary industry is distributed in the peripheral areas. In general, a strip-shaped urban spatial structure with a strong main center, weak subcenter and multiple groups is present. Improving the complexity of urban functional space is an important goal of spatial structure optimization. ISPRS Int. J. Geo-Inf. 2020, 9, 92 2 of 26 that influence the urban spatial structure, such as knowledge and information, which enhance the traditional physical production factors such as land and labor [4]. Due to the arrival of the era of new data, an increasing amount of urban research is carried out by using a wide variety of geoscience new data. The applied data mainly focus on items such as the map POI (point of interest) data that describe the geospatial entities, GPS track data, and mobile phone signaling data related to crowd activities [5][6][7][8][9][10][11][12]. POI data, as a new spatial data source, have an important application potential. In this paper, POI refers to some geographical entity, which is closely related to human life. And in a geographic information system, POI can be a commercial outlet, a bus stop, a high-rise building, etc., which are more authentic. Therefore, POI data can largely enhance the capacity of the description of the physical location, reflect city activities, and can be effectively applied to the urban spatial structure research [13]. Compared with traditional data, POI data not only have the advantages of a large sample and easy access, but can also represent the spatial distribution of social and economic activity intensity and functional composite utilization, and reflect more accurately urban spatial structure [14,15]. In this context, research on the combination of traditional urban space and geographic new data is in urgent need of empir...
Nanoindentation testing of the titanium oxide/titanium system with electrochemically grown oxide films exhibits permanent deformation prior to a yield excusion, indicating that the occurrence of this suddent discontinuity is predominantly controlled by oxide film cracking rather than dislocaton nucleation and multiplication. Observations of circumferential cracking also lend support to this explanation. A model has been developed to predict the mechanical response prior to oxide fracture for the case of a hard coating on a soft substrate. During loading contact, the hard coating undergoes elastic deflection which may include both bending and membrane stretching effects, while the substrate is elastoplastically deformed. The model works well for surface films thicker than 20 nm. Additionally, the maximum radial tensile stress in anodically grown titanium oxide, which is responsible for film cracking at the critical load, is approximately 15 GPa.
Together, the regional economy, tourism industry, and ecological environment form mutually interactive and interdependent relationships. Therefore, a better understanding of their evolutionary relationships could help reveal the spatial-temporal evolution patterns of their coordinated development and promote a successful implementation of strategies for regional sustainable development. By choosing the 14 cities (12 cities and 2 city-level prefectures) in Gansu Province as cases, this study establishes the respective evaluation indices for assessing the coordinated developmental level of the tourism system. With a combination of varying quantitative methods including order parameter analysis, fuzzy membership classification, regression analysis and gray correlation analysis, measurement models for assessing the coordinated developmental level and analyzing the associated spatial-temporal evolution patterns are established between 2000 and 2016. The conclusions are as follows. Between 2000 and 2016, the development of the regional economy, tourism industry, and ecological environment mutually reinforced one another in Gansu Province. Overall, the coordinated developmental level kept gradually improving over time. However, the development of the ecological environment lagged behind that of the tourism industry and economic growth, and synchronous and coordinated development among these three subsystems was not achieved. The overall level of coordination among 14 cities was also gradually improved, as manifested by the good level of coordinated development. However, spatial differences still existed.
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