Search Results (6)

The Low Earth Orbit (LEO) small satellites are extensively used for global connectivity to enable services in underpopulated, remote or underdeveloped areas. Their inherent broadcast nature exposes LEO–terrestrial communication links to severe security threats, which always reveal new challenges. The secrecy performance of the satellite-to-ground user link in the presence of a ground eavesdropper is studied in this paper. We observe both scenarios of the eavesdropper’s channel state information (CSI) being known or unknown to the satellite. Throughout the analysis, we consider that locations of the intended and unauthorized user are both arbitrary in the satellite’s footprint. On the other hand, we analyze the case when the user is in the center of the satellite’s central beam. In order to achieve realistic physical layer security features of the system, the satellite channels are assumed to undergo Gamma-shadowed Ricean fading, where both line-of-site and scattering components are influenced by shadowing effect. In addition, some practical effects, such as satellite multi-beam pattern and free space loss, are considered in the analysis. Capitalizing on the aforementioned scenarios, we derive the novel analytical expressions for the average secrecy capacity, secrecy outage probability, probability of non-zero secrecy capacity, and probability of intercept events in the form of Meijer’s G functions. In addition, novel asymptotic expressions are derived from previously mentioned metrics. Numerical results are presented to illustrate the effects of beam radius, satellite altitude, receivers’ position, as well as the interplay of the fading or/and shadowing impacts over main and wiretap channels on the system security. Analytical results are confirmed by Monte Carlo simulations. Full article

One current global problem is the shrinkage of rural areas, which is expected to become an increasingly recurrent dynamic caused by the transformations in land uses and forms of habitation of the contemporary era. Patagonia is a suitable case study to understand the processes and challenges exposed by rural shrinkage, which not only addresses population loss but also the causes and consequences that transform rural territories. Its remote geographical location and climate conditions make it a complex place for human settlement. The objective is to describe the relationship between the agrarian structure and rural population decline in Chilean Patagonia. Taking a mixed methodological approach that combines the geohistorical review of settlement processes and the use of statistical procedures with census data, the presence of significant inequalities in the distribution of land and the accumulation of areas in large properties is discussed. The loss of rural population was identified, which may be driven by unequal access to land favoring concentration for extractive activities such as large-scale sheep farming, hydrocarbons and biofuels production. This prompts the exodus of young people to urban centers in search of work and education because land grabbing limits economic options, and rural depopulation reduces service coverage without timely responses from political institutions. This has caused the rural shrinkage in territories with demographic imbalances, with high aging and masculinization rates that hinder the repopulation of these areas, which have historically suffered from underpopulation. In conclusion, population strategies in these areas based on extractivism and a strict land ownership regime have not facilitated permanent human settlement but have instead complicated it more. Full article

Cabo Ortegal, in Spain, was declared a UNESCO Global Geopark in 2023. An ultramafic complex makes it a geologically exciting unit, where many research works have been carried out. Serpentinites, formed by the weathering of peridotites, dunites, and other ultramafic rocks, have been described in detail in previous works. Their role as a construction material has been elucidated, although due to their complexity and heterogeneity, the results of using these materials for construction are not always successful. Talcose rocks, related to serpentinites, can also be found in the complex, although it is difficult to distinguish them. Talcose rocks may be a resource to be explored and exploited in an unpopulated area. The use of talc in pharmaceuticals, cosmetics, and handicrafts makes it a material of growing importance. However, the asbestos and heavy metal content should be severely limited to prevent health issues. The goal of this work is to start the characterization of these talcose rocks before promoting their potential use in different contexts to support the economy of an underpopulated area of Spain. Full article

Depopulation is occurring in rural areas of Japan due to the outflow of the population to urban areas, the declining birthrate, and the aging population. Within depopulated areas, there is a problem of declining accessibility to medical facilities due to the decline of the medical system and transportation infrastructure. Therefore, measuring accessibility to medical facilities in underpopulated areas is an important issue. In this study, we calculated an accessibility index (APMI) to medical facilities in underpopulated areas in Japan using geographical information such as elevation, distance to medical facilities, and distance to bus stops. Furthermore, we estimated the number of patients who are considered to have difficulty visiting hospitals by using the National Health Insurance data (KDB) owned by all local governments in Japan. Through the analysis in this study, it became clear that accessibility was extremely low in the mountainous area of Hakui, Ishikawa Prefecture, and the number of patients living there could be determined. In addition, priority areas for improving the environment for visiting the hospital were identified. Full article

Artificial intelligence (AI) in medical care can raise diagnosis accuracy and improve its uniformity. This study developed a diagnostic imaging system for chronic wounds that can be used in medically underpopulated areas. The image identification algorithm searches for patterns and makes decisions based on information obtained from pixels rather than images. Images of 50 patients with pressure sores treated at Kobe University Hospital were examined. The algorithm determined the presence of necrosis with a significant difference (p = 3.39 × 10⁻⁵). A threshold value was created with a luminance difference of 50 for the group with necrosis of 5% or more black pixels. In the no-necrosis group with less than 5% black pixels, the threshold value was created with a brightness difference of 100. The “shallow wounds” were distributed below 100, whereas the “deep wounds” were distributed above 100. When the algorithm was applied to 24 images of 23 new cases, there was 100% agreement between the specialist and the algorithm regarding the presence of necrotic tissue and wound depth evaluation. The algorithm identifies the necrotic tissue and wound depth without requiring a large amount of data, making it suitable for application to future AI diagnosis systems for chronic wounds. Full article

This study aims to develop a better understanding of what drives small and medium-sized enterprises (SMEs) to engage in environmental practices in isolated rural areas. Despite a growing literature on environmental behavior in different contexts, the green activities of SMEs in rural areas remains underexposed. This neglect is remarkable, and deserves attention given the serious depopulation problems they have to face, and the economic and social challenges that lie ahead. Using unique data from 141 SMEs in one of the most sparsely populated regions in the European Union, we study the influence of territorial relations on firms’ environmental conduct. Our results suggest that different territorial factors have some impact on the adoption of environmental practices. We report evidence indicative of the role of these factors in shaping environmental decisions. Finally, we offer suggestions for future research that could further develop our understanding of environmental management decisions in rural and underpopulated areas. Full article