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To reduce the structural deterioration of mass concrete structures from temperature cracks, and lower energy consumption caused by the traditional mass concrete hydration heat cooling process, this paper reports the preparation of concrete temperature-controlled phase change aggregate (PCA) by a vacuum compaction method using light and high-strength black ceramite and No. 58 fully refined paraffin wax as phase change material (PCM), and the encapsulation technology of the aggregate by using superfine cement and epoxy resin. Further, through laboratory tests, the cylinder compressive strength, thermal stability and mixing breakage rate of the encapsulated PCA were tested, and the differences in mechanical properties such as compressive strength, flexural strength and splitting tensile strength between phase change aggregate concrete (PCAC) and ordinary concrete were studied. A test method was designed to test the heat storage effect of PCA, and the temperature control effect of PCAC was analyzed based on the law of conservation of energy. The research conclusions are as follows: (1) Both superfine cement and epoxy resin shells increase the strength of the aggregate, with the epoxy resin increasing it more than the superfine cement. The thermal stabilization of the PCA is good after encapsulation of superfine cement and epoxy resin. However, PCA encapsulated in superfine cement is more easily crushed than that encapsulated in epoxy resin. (2) Under the condition of water bath heating and semi-insulation, when the water bath temperature reaches 85 °C, the temperature difference between the PCA and the common stone aggregate can be up to 6 °C. Based on the law of energy conservation, the test results will be converted to mass concrete with the same volume of aggregate mixture;, the difference of PCAC and ordinary concrete temperature can be up to 10 °C, so the temperature control effect is significant. (3) The mechanical properties of PCAC with 100% aggregate replacement rate compared to ordinary concrete are reduced to varying degrees, and the performance decline of the epoxy-encapsulated PCA is smaller than that encapsulated with superfine cement; in an actual project, it is possible to improve the concrete grade to make up for this defect. [ABSTRACT FROM AUTHOR]

In recent years, with the continuous expansion of the global cruise tourism market, global and regional cruise shipping networks have gradually formed and improved. Among them, the Caribbean cruise shipping network is particularly mature and complex, with a typical regional spatial organization. This paper takes cruise routes as the starting point to analyze the basic characteristics of the Caribbean cruise shipping network, investigate their hierarchical structure and spatial differentiation characteristics, and summarize the general spatial laws of a regional cruise shipping network. The results show that Caribbean cruise routes are mostly circular, and some of them have multi-circular sections. Medium and short cruise routes are common, and most cruise routes usually include sailings that last for a week. The cruise network forms an inverted V shape with the Florida Peninsula as the core connecting the eastern and western Caribbean Seas. There are differences in the number of sailings and centrality of different ports, thus forming the functional differentiation of core hub ports, functional hub ports, and general ports. The Caribbean cruise shipping network is divided into different hierarchies; with the increasing complexity of hierarchies, the numbers of ports and shipping groups have increased, the number of sailings and the centrality show rising trends, and the structure of the cruise shipping network tends to be complicated and the coverage tends to be broad. The three hierarchies basically reflect the core, skeleton, and overall pattern of the Caribbean regional cruise shipping network, and the core hierarchy includes most of the core hub ports. [ABSTRACT FROM AUTHOR]

Parks are an important place for residents to relax. An equitable distribution of parks can promote social equity and enhance the residents' welfare. The service areas of parks are affected by the mode of transport. As public transport is a green and economic travel mode with a wide range of applications, we identified the service area of parks based on the accessibility of public transport. On this basis, the problem of park layout was analyzed. The results show that: (1) the coverage rate for the park service areas decreased from the center of Beijing to the periphery. The subdistricts around employment districts have a high coverage of park services, whereas some suburban subdistricts lack services. (2) The spatial form of PSAs can be affected by factors such as railways, water courses, and the topography, so there are service gaps for some 48 parks, which are mainly located outside the Fourth Ring Road area. (3) A poor allocation of public transport resources has aggravated the uneven distribution of the park services. Areas with few parks also have poor public transportation conditions. [ABSTRACT FROM AUTHOR]

Since the new century, countries in Africa have started a new round of rail network planning and construction which brings the completed different features together with the spatial organization of the railway network during the colonial period. Along with the strategic layout of "going out" with China's railways, the organizational structure of the African railway network will make a tremendous change for the construction market, network organization, and gauge structure of the African railways. Based on the literature reviews, we analyzed and forecasted the evolution of railway network in Africa and discussed the spatial differentiation of the future construction market of the railways from the view of country and enterprise. The results show that the development of the African railway networks will experience three stages: 1850–1960, 1960–2010 and 2010–2050, and that the organization pattern of the African railway network has evolved from the "Hinterland-Port" model to the "Continental Integration" model. The development of railway technical standards tends to be integrated, the gauge type is changed from complicated to single, the gauge distribution is changed from broken to uniform. The contractor countries of the railway changed from English-French dominated to China dominated. The application of railway technical standards is influenced by technology dependence and path dependence and is mainly reflected in the two characteristics of "Chinese standard implantation" and "local standard retention". The contractor enterprises of railway have a monopoly on the market of a country, CCECC and CRCC are leading, and the contractor enterprises are spatially characterized by four spatial distribution modes: single, continuous, jumping and comprehensive. [ABSTRACT FROM AUTHOR]

Urban integration, a new concept in urban and regional research, is an inevitable outcome of urban development. Based on accessibility analysis, this study uses urban and road network data to identify urban pairs in Northeast China which meet the distance threshold for urban integration and establishes an index system to evaluate the development potential. The research shows that in Northeast China, the results for urban integration are similar to those for the present urban structure in China, that is, a spatial pattern with provincial capital cities at the core and an urban belt as the axis. According to the evaluation, areas with potential for urban integration may be classified into four categories, namely, dominant areas, key areas, ordinary areas, and alternative areas. The candidate and potential areas for urban integration tend to be concentrated near a provincial capital city or a regional development zone. The results show that the development potential for urban integration varies greatly among the different urban pairs and the main constraining factors are different for each location. Among the constraining factors, the commuting time, costs, and economic conditions for the citizens are the most important. [ABSTRACT FROM AUTHOR]

Special functional areas and poor areas tend to spatially overlap, and poverty is a common feature of both. Special poor areas, taken as a kind of "policy space," have attracted the interest of researchers and policymakers around the world. This study proposes a basic concept of special poor areas and uses this concept to develop a method to identify them. Poor counties in China are taken as the basic research unit and overlaps in spatial attributes including old revolutionary bases, borders, ecological degradation, and ethnic minorities, are used to identify special poor areas. The authors then analyze their basic quantitative structure and pattern of distribution to determine the geographical bases' formation and development. The results show that 304 counties in China, covering a vast territory of 12 contiguous areas that contain a small population, are lagging behind the rest of the country. These areas are characterized by rich energy and resource endowments, important ecological functions, special historical status, and concentrated poverty. They are considered "special poor" for geographical reasons such as a relatively harsh natural geographical environment, remote location, deteriorating ecological environment, and an inadequate infrastructure network and public service system. Some areas suffer from underdevelopment and even lack the infrastructure for basic living. In order to prevent further deterioration of the economic, social, and ecological environments in these areas, targeted policies need to be implemented. [ABSTRACT FROM AUTHOR]

Cruise tourism is an obviously global industry in different dimensions. From a geographical perspective, cruise ships are mobile and capable of being repositioned at a company's notice, which forms the inherent basis for its global spatial layout. As a branch of the cruise industry, the world cruise is clearly globalizing in geographical space by offering long itinerary, even round-the-world trips, for everyone. Using the schedule data from 2018 to 2019, this paper analyzes the spatial characteristics of the itinerary and port organization of Cunard, a world cruise company. We find that the itinerary distribution and port organization of Cunard are both globalization and regionalization, and the latter is the core and main component of the former. Under the influence of the COVID-19 epidemic, the global mobility of cruises has ground to a halt, while local mobility offers the possibility of its resumption as soon as possible. Turning to the regional voyage with the shorter and simple itinerary is feasible for Cunard and other world cruises, which is conducive to the realization of the resuming voyage as soon as possible. Moreover, strict boarding and safety onboard are essential. [ABSTRACT FROM AUTHOR]