Search

The cloud storage system provides users with convenient storage services. However, users who use cloud storage services lose absolute control over the data once they upload files to the cloud service provider (CSP). The integrity of the cloud data has become a problem worth considering. In the realization of verification of cloud storage schemes, a third-party auditor (TPA), as a professional organization that provides users with public audit services, is an indispensable and important entity. However, the TPA is not entirely credible because the TPA may perform audits dishonestly out of laziness or selfishness. Based on the above considerations, we provide a scheme for solving the problem of cloud data integrity verification and the TPA dishonesty based on identity-based encryption (IBE). The proposed identity-based public auditing verification scheme can provide security against malicious auditors. In this scheme, the mathematical design is based on IBE, which frees the users from complicated certificate management. In addition, during the public auditing phase, adding a timestamp can effectively prevent the malicious TPA from working dishonestly. Moreover, the security analysis and performance evaluation of the scheme for the untrusted CSP and semi-trusted TPA shows effective results.

Rapid urbanization has led to the sharp decline of some rural villages. Idle rural residential land (IRRL) is symbolic of rural decline, and the academic community is in urgent need of quantitative studies on the spatial pattern of IRRL from the perspective of geography. Taking Pinggu as a case area, we explored the spatial pattern and layout mode of IRRL and evaluated its utilizability and reuse under different spatial layout modes. Our findings show that the idle rate of rural residential land (RRL) in Pinggu, which is in a suburb of a metropolis, is more serious than that of urban land. The patches of IRRL are generally small and fragmented, showing the characteristics of overall dispersion and local agglomeration of the whole area. The agglomerative point type and scattered point type are the main spatial layout modes of IRRL. In villages, the spatial distribution of IRRL is characterized by a small and scattered point distribution, and large-area polygon agglomeration and belt agglomeration are relatively less common. The utilizability of IRRL in Pinggu decreases from the urban fringe to the surrounding rural area. The utilizability of the agglomerative polygon type, agglomerative belt type, and agglomerative point type in the urban suburbs and agricultural plains areas is higher, while the utilizability of the scattered strip type and scattered point type in the northern and eastern suburban mountainous areas is lower. Our research contributes to filling the gap in the geographical quantitative research on IRRL by exploring the interactions between humans and land under rural decline and providing a theoretical basis for the revitalization of declining rural areas and the coordinated development of urban and rural areas.

Rural settlements, a type of rural locality where residents live and engage in production, always face significant changes and transitions when meeting the demands of rural development. By applying an integrated framework, we developed a new way to quantify the rural settlement transition (RST) through analysis of the interaction between population movements and land use changes and identification of the coupling relationship between the RST and rural development. This study revealed the dynamic process of the RST by calculating the per capita rural settlement area (PCRA) based on samples collected from 1996 to 2016 in Shandong Province. Our findings show that the rural population first decreased and then reached a relatively stable state, whereas the area of rural settlements experienced a rapid decline after a short increase in Shandong. However, the spatial patterns of rural population and rural settlements are similar to each other. In terms of the spatiotemporal characteristics of the RST, the PCRA shifted from growth to reduction in different periods and showed a spatially increasing tendency from downtown areas to suburban areas and then to exurban areas. The coupling relationship between the RST and rural development changed from extensive to intensive development during the process of urbanization. The coordinated interaction between the rural population movement and land use changes contributed to the sustainable RST as well as to rural development. Based on these findings, this paper also offers a critical discussion of the Chinese rural development policy, arguing that the land consolidation and integrated urban-rural land use planning derived from the RST should be taken into account by Chinese policy-makers and planners as viable strategies for achieving sustainable rural development targets.

Idle rural residential land (IRRL) is an important manifestation of changes in the human-land relationship during rural development. Studies on this topic form an important field in the study of sustainable land use, but quantitative analyses of IRRL in the academic community are still lacking. In this paper, we take Pinggu District, a metropolitan suburb that has experienced rapid urbanization, to analyze the spatial differentiation of IRRL and explore the spatial differentiation in the impact of different factors on IRRL. Our findings showed that IRRL was a common phenomenon in Pinggu. There was a spatial pattern of “one belt, three cores” in Pinggu District, and its scale decreased from the southeast to the northwest. Industrial areas, semimountainous ecotourism areas and urban fringe areas were the high-incidence areas of IRRL, while the idle rate of rural residential land in mountainous areas and agricultural areas on the plain was relatively low. The IRRL was the result of a combination of different factors, and there were differences among the factors and regions. The transfer of rural labor, nonagriculturalization of the industrial structure and the mode of production and lifestyle caused by urbanization and industrialization were the major driving forces, and the lagging village planning and imperfect land use system increased the risk of IRRL at the management level. Our study contributes to filling the gap in quantitative research on IRRL to enrich the research regarding the land use system by exploring the interaction between humans and land in rural areas and thus has significance for the rural restructuring and sustainable use of land in China.

The function of rural housing land is an important manifestation of the living needs of farmers. Multifunctional research on rural housing land can provide a scientific basis for the formulation of practical and effective systems of rural housing land. Based on the survey data of 613 typical farmers, this paper identifies each function, analyzes functional spatial distribution features of rural housing land by using the kernel density estimation method, and constructs a multinomial logistic regression model to quantitatively measure the influencing factors and to reveal the mechanism of functional spatial distribution under the combined effect of the “farmers--rural housing land--village” system. This research shows the following: 1) Rural housing land has mainly a social security function(SSF), while a profit function(PF) and a retaining function(RF) have also appeared, with the proportions being 71.78%, 10.60% and 17.62%, respectively in the Pinggu District of Beijing. 2) SSF is strongest in the economically depressed mountainous areas, whereas PF and RF are strongest in the economically developed plain areas and the economically secondary semimountainous area, with the proportions being 77.31%, 15.91% and 22.10%, respectively. Various functions present a spatial gradient change. 3) Agglomeration analysis shows that SSF presents two strong cores: the hilly and mountainous areas in the far north and the plain areas in the suburbs with a better economy, with the “point-surface” distribution. PF concentrated in the tourist spots in the hilly and mountainous areas, the urban belt vicinity with a good economy and the MF industrial park, with the “point-and-belt” pattern. RF focused in the economically secondary semimountainous area and the industrial zone in the southwestern part of the city, showing a “multiband” shape. 4) The function of rural housing land arises from the farmers' needs according to conditions of their own family and rural housing land under the positioning of certain villages. The village characteristics, such as economy, are external factors that present a continuous adjustment effect on the function of rural housing land with the form of long-term action; the characteristics of rural housing land, such as location, are restrictive factors that show two-way feedback effects on the function of rural housing land with the form of foundational action. Both the family characteristics, such as non-agricultural income ratio, and the householder characteristics, such as age, are internal factors that present stage stimulating effects on the function of rural housing land with the form of direct action. 5) Trying to divide the right of use and qualification of RF housing, the right of use of PF housing, through innovating acquisition system of rural housing land and constructing mechanism of rural housing land replaces town security room, which aim to improve the functional efficiency of rural housing land.

The change in urban construction land (UCL) and rural residential land (RRL) and their coupling relationship are the main manifestation of urban-rural construction land transition (URCLT) and the mapping of urban-rural factor flow. It is of great significance to systematically understand and master its laws for expanding the theory of land use transition (LUT) and adjusting the man-land relationship between urban and rural area. This paper constructs a theoretical model of URCLT, analyses the spatial and temporal characteristics of urban and rural construction land (UARCL) scale, elasticity and structure transition in Shandong Province from 1996 to 2015, reveals the transition process and coupling mechanism of UCL and RRL by using the method of geographic detector. The research shows that the UCL and RRL in Shandong Province have evolved along a coordinated track of increase and decrease as a whole, but with certain periodic fluctuations, resulting in insufficient elasticity and structural transition of URCLT. The rationalization degree of UCL growth was reduced, the low synchronization and non-synchronization of RRL reduction predominates, while the dominant type of urban-rural human-land relationship changed from urban-rural (UR) increase or decrease coordinated to both urban (U) and rural (R) increase uncoordinated. The URCLT had obvious spatial differences. The UARCL in the “blue-yellow” economic zone and the provincial capital urban agglomeration was active, but was dominated by uncoordinated transition, and the non-synchronization reduction of RRL was dominant. The factors influencing the transition of URCL were complex, diverse and unstable, and the transition mechanism was the interaction process of self-regulation of population, industry and land elements within the urban and rural system and intervention of external natural environment, science and technology and institutional policies.