Search Results (4,049)

Cracking in concrete box girder bridges will have a significant impact on the safety and durability of the structure, and many box girder bridges which are in service have undergone varying degrees of cracking. Currently, the safety design of actual bridge projects place an emphasis on the stress or the load value of a cross section at the limit value specified in the code for safety control. This design method assumes that the member itself is of uniform and continuous material and is internally undamaged. However, the bridge structure is more or less cracked to varying degrees during the period from casting to construction to operation of the concrete members. In this paper, a finite element computational model of a three-span prestressed concrete box girder bridge with existing cracks is established based on the fracture mechanics theory, and the critical parameters of crack extension are introduced to evaluate the extension state of cracks. At the same time, the extended stability of the existing cracks of the box girder bridge is analyzed by considering the temperature effect, vehicle loading, and prestressing loss, and the sensitivity of crack extension under each working condition is investigated. The results show that, with the increase in crack length and depth, the crack expansion is promoted, but the effect is relatively small, and the maximum stress intensity factor is only 6.48 MPa mm^1/2. Under the multi-factor coupling effect, the cracks show a composite crack expansion dominated by type I cracks, the longitudinal cracks of the existing base plate are in a stable state, the maximum value of the crack expansion critical parameter of the vertical cracks of the webs reaches 1.087, and there is a tendency to expand locally. The maximum value of the critical parameter for crack extension of the vertical crack in the web plate reaches 1.087, and there is a tendency towards local expansion. The crack extension evaluation criteria proposed in this paper have a certain reference value for crack extension research on similar concrete box girder bridges and provide a scientific basis for the optimized design of similar bridges. Full article

Outdoor positioning has become a ubiquitous technology, leading to the proliferation of many location-based services such as automotive navigation and asset tracking. Meanwhile, indoor positioning is an emerging technology with many potential applications. Researchers are continuously working towards improving its accuracy, and one general approach to achieve this goal includes using machine learning to combine input data from multiple available sources, such as camera imagery. For this active research area, we conduct a systematic literature review and identify around 40 relevant research papers. We analyze contributions describing indoor positioning methods based on multimodal data, which involves combinations of images with motion sensors, radio interfaces, and LiDARs. The conducted survey allows us to draw conclusions regarding the open research areas and outline the potential future evolution of multimodal indoor positioning. Full article

Insect pollination services amount to USD 235–577 billion. Seventy five percent of agricultural production for human consumption depends on pollination, mainly by bees. A decline in pollinators, including Meliponini tribe bees, will impact the economy, food security, human health, and ecosystem stability, especially in tropical forests where stingless bees are the main pollinators. The objective of this survey was to understand the relationship between good management practices and nest losses in meliponiculture, encompassing biosecurity and conservation criteria. A 36-question survey was organized and spread. We received 92 responses, representing 4548 managed nests. The primary motivation for engaging in meliponiculture was biodiversity conservation (92%). More than 50% of the questions on biosecurity were answered as “applied”. Hand washing before any activity with bees was the main rule, followed by material sterilization and personal protective equipment use. The annual mortality rate of stingless bee nests was estimated at 15%. Nest invaders (72%) and nearby sources of pollution (60%) were identified as the main potential causes of nest losses. From a general perspective, meliponiculture practices continue to expand remarkably. The implementation of effective nest management strategies is associated with a reduction in nest losses. It is important to consider One Health’s perspective to ensure optimal management practices. Full article

Hyperboloid cooling towers are counted among the largest cast-in-place industrial structures. They are an essential element of cooling systems used in many power plants in service today. Their main structural component, a reinforced-concrete shell in the form of a one-sheet hyperboloid with bidirectional curvature continuity, makes them stand out against other towers and poses very high construction and service requirements. The safe service and adequate durability of the hyperboloid structure are guaranteed by the proper geometric parameters of the reinforced-concrete shell and monitoring of their condition over time. This article presents an original concept for employing terrestrial laser scanning to conduct an end-to-end assessment of the geometric condition of a hyperboloid cooling tower as required by industry standards. The novelty of the proposed solution lies in the use of measurements of the interior of the structure to determine the actual thickness of the hyperboloid shell, which is generally disregarded in geometric measurements of such objects. The proposal involves several strategies and procedures for a reliable verification of the structure’s verticality, the detection of signs of ovalisation of the shell, the estimation of the parameters of the structure’s theoretical model, and the analysis of the distribution of the thickness and geometric imperfections of the reinforced-concrete shell. The idea behind the method for determining the actual thickness of the shell (including its variation due to repairs and reinforcement operations), which is generally disregarded when measuring the geometry of such structures, is to estimate the distance between point clouds of the internal and external surfaces of the structure using the M3C2 algorithm principle. As a particularly dangerous geometric anomaly of hyperboloid cooling towers, shell ovalisation is detected with an innovative analysis of the bimodality of the frequency distribution of radial deviations in horizontal cross-sections. The concept of a complete assessment of the geometry of a hyperboloid cooling tower was devised and validated using three measurement series of a structure that has been continuously in service for fifty years. The results are consistent with data found in design and service documents. We identified a permanent tilt of the structure’s axis to the northeast and geometric imperfections of the hyperboloid shell from −0.125 m to +0.136 m. The results also demonstrated no advancing deformation of the hyperboloid shell over a two-year research period, which is vital for its further use. Full article

The increasing demand for food and the overexploitation of natural resources rapidly deplete the planet’s ecosystems, highlighting the urgent need for sustainable alternatives. Nature-based solutions effectively promote agricultural sustainability and environmental conservation but require continuous financial and political support to overcome existing barriers. This research examines these solutions’ effectiveness in Santa María Jacatepec, a biocultural region of Indigenous peoples in the Papaloapan Basin, Oaxaca, Mexico. A mixed-methods approach combining quantitative and qualitative analyses uses National Institute of Statistics and Geography data to evaluate socioeconomic and environmental indicators. The results indicate that despite pressures to develop cattle ranching, communities have maintained rain-fed agriculture, especially the milpa system, ensuring food sovereignty and preserving agricultural biodiversity. Additionally, implementation of Voluntarily Conserved Areas has facilitated access to payments for environmental services, incentivizing ecosystem protection. However, financial and structural challenges persist, limiting the expansion of these solutions. Santa María Jacatepec exemplifies how Indigenous communities can apply nature-based solutions to strengthen agricultural sustainability and environmental conservation. Integrating traditional knowledge and strengthening conservation policies can enhance community resilience and ensure sustainable development amid increasing pressure on natural ecosystems. Full article

The pivotal aspects of enhancing regional ecosystem services and augmenting socioeconomic growth lie in optimizing the land-space development and protection strategies, coupled with the establishment of a robust ecological network (EN). This article examines the Poyang Lake area and employs the MOP model, NSGA-II, and PLUS model to determine the best sustainable land use strategy. Subsequently, the MSPA, InVEST model, circuit theory, complex network, and others are employed to construct and analyze the land-space EN across three time periods. Ultimately, the EN is optimized based on spatial protection priority, ecological obstacle areas, and ecological nodes. The results show the following: (1) From 2005 to 2035, more construction land will be developed around the Greater Nanchang area and other urban centers. In the BAU scenario, construction land will expand faster, while cultivated land, forest, grassland, and bare land will continue to decline. In the SD scenario, the alteration to comparable land is minimal, the growth rate of construction land will slow, cultivated land, forest, grassland, and bare land will all decline little, and the water area will increase slightly; (2) While the area of ecological sources is decreased and ecological corridors become longer and narrower in the BAU scenario, the spatial distribution of ENs in different periods is small, and the quantitative structure and spatial distribution of ecological sources and corridors are essentially unchanged in the SD scenario; (3) Based on the topological structure of ENs, it is found that the clustering of nodes in the SD scenario is more obvious, the importance of ecological sources is enhanced, the efficiency of information transmission is improved, and the radiation range is wider and more stable; (4) The greatest priority ecological sources in each period are concentrated around Poyang Lake. In the SD scenario, the priority of ecological sources improves, and 7025 km² of ecological obstacle restoration area is identified, with 41, 31, and 36 ecological breakpoints in the first, second, and third levels. The study’s findings can assist and shape theoretical and practical approaches to land governance and sustainable development in great lake areas. Full article

The concept of intelligence has many applications, such as in coatings and cyber security. Smart coatings have the ability to sense and/or respond to external stimuli and generally interact with their environment. Self-healing coatings represent a significant advance in improving material durability and performance using microcapsules and nanocontainers loaded with self-healing agents, catalysts, corrosion inhibitors, and water-repellents. These smart coatings can repair damage on their own and restore mechanical properties without external intervention and are inspired by biological systems. Properties that are affected by either momentary or continuous external stimuli in smart coatings include corrosion, fouling, fungal, self-healing, piezoelectric, and microbiological properties. These coating properties can be obtained via combinations of either organic or inorganic polymer phases, additives, and pigments. In this article, a review of the advancements in micro/nanocapsules for self-healing coatings is reported from the aspect of extrinsic self-healing ability. The concept of extrinsic self-healing coatings is based on the use of capsules or multichannel vascular systems loaded with healing agents/inhibitors. The result is that self-healing coatings exhibit improved properties compared to traditional coatings. Self-healing anticorrosive coating not only enhances passive barrier function but also realizes active defense. As a result, there is a significant improvement in the service life and overall performance of the coating. Future research should be devoted to refining self-healing mechanisms and developing cost-effective solutions for a wide range of industrial applications. Full article

The N policy is a buffer and transmission management scheme proposed for nodes in wireless sensor networks to save energy. It exploits the concept that the output radio of a node is initially switched off until a critical queue of packets is built up. Then, the output transmission begins and continues until the buffer is completely flushed. The cycle then repeats. In this study, we analyze a buffer with the N policy, equipped additionally with active queue management, which allows for dropping some packets depending on the current buffer occupancy. This extension enables controlling the performance of the node to a much greater extent than in the original N policy. The main contribution is the formulae for the key performance characteristics of the extended policy: the queue size distribution, throughput, and energy efficiency. These formulae are proven for a model with a general distribution of service time and general parameterizations of active management during the energy-saving and transmission phases. Theoretical results are followed by sample numerical calculations, demonstrating how the system’s performance can be controlled using active management in the transmission phase, the energy-saving phase, or both combined. The influence of the threshold value in an actively managed buffer is then shown and compared with its passive counterpart. Finally, solutions to some optimization problems, with the cost function based on the trade-off between the queue length and throughput, are presented. Full article

As humans continue to exploit the ocean, the number of UAV nodes at sea and the demand for their services are increasing. Given the dynamic nature of marine environments, traditional resource allocation methods lead to inefficient service transmission and ping-pong effects. This study enhances the alignment between network resources and node services by introducing an attention mechanism and double deep Q-learning (DDQN) algorithm that optimizes the service-access strategy, curbs action outputs, and improves service-node compatibility, thereby constituting a novel method for UAV network resource allocation in marine environments. A selective suppression module minimizes the variability in action outputs, effectively mitigating the ping-pong effect, and an attention-aware module is designed to strengthen node-service compatibility, thereby significantly enhancing service transmission efficiency. Simulation results indicate that the proposed method boosts the number of completed services compared with the DDQN, soft actor–critic (SAC), and deep deterministic policy gradient (DDPG) algorithms and increases the total value of completed services. Full article

Objectives: Estimating the risk of diabetes mellitus (DM) is important for the proper management of patients with spinal cord injury (SCI). We investigated the short-term and long-term risks of DM among patients with SCI, according to the presence or severity of post-SCI disability and the level of injury. Methods: We conducted a retrospective cohort study using the Korean National Health Insurance Service (2010–2018) database. After matching by age and sex, 6129 SCI patients and 22,979 controls were included. The primary outcome was incident DM, and risk was evaluated for both the short term (within 1 year after SCI) and the long term (after 1 year of SCI diagnosis). Results: The risk of DM was higher among patients with cervical- and thoracic-level SCI accompanied by disability compared to the controls during follow-up (4.6 ± 2.6 years). The short-term risk of DM was higher among patients with SCI (odds ratio [OR] 2.51, 95% confidence interval [CI] 1.91–3.27) than among the controls and it was even higher among patients with severe disability (OR 5.38, 95% CI 2.91–9.27). According to the level of injury, patients with cervical SCI had the highest short-term risk of DM (with disability, OR 4.93, 95% CI 3.07–7.63). There was no significant increase of DM risk in the long term, after 1 year of SCI diagnosis. Conclusions: Patients with SCI accompanied by severe disability and cervical-level injury had higher risks of pronounced DM in the short term. The findings of this study emphasize the need for active surveillance of DM among patients with high-level SCI and disability, especially in the short term, in addition to continuous monitoring and proper management of DM in the long term. Full article

Moisture accelerates the degradation of asphalt properties, significantly impacting the service life of roads. Therefore, this study uses simplified viscoelastic continuous damage theory and employs frequency scanning, linear amplitude scanning, and fatigue–healing–fatigue tests with a dynamic shear rheometer. The objective is to investigate the effects of aging time, moisture conditions, and aging temperature on the fatigue and self-healing performance of SBS (Styrene–Butadiene–Styrene block copolymer)-modified asphalt, nano-SiO₂-modified asphalt, and nano-SiO₂/SBS composite modified asphalt in a moisture-rich environment. The results indicate that nano-SiO₂ powder enhances the low-temperature performance of modified asphalt, whereas the SBS modifier reduces temperature sensitivity and increases the recovery percentage after deformation. Compared to SBS-modified asphalt, the deformation resistance of nano-SiO₂/SBS composite modified asphalt has increased by about 30%, while nano-SiO₂-modified asphalt shows relatively poor deformation resistance. The fatigue performance of SBS-modified asphalt deteriorates under moisture, whereas the addition of nano-SiO₂ powder improves its fatigue life. Nano-SiO₂/SBS composite modified asphalt exhibits strong self-healing capabilities. Although self-healing can enhance the fatigue life of modified asphalt, moisture inhibits this improvement after self-healing. Full article

Exploring the dynamic response of land use and ecological vulnerability (EV) to future climate change and human ecological restoration policies is crucial for optimizing regional ecosystem services and formulating sustainable socioeconomic development strategies. This study comprehensively assesses future land use changes and EV in the Yellow River Basin (YRB), a climate-sensitive and ecologically fragile area, by integrating climate change, land management, and ecological protection policies under various scenarios. To achieve this, we developed an EV assessment framework combining a scenario weight matrix, Markov chain, Patch-generating Land Use Simulation model, and exposure–sensitivity–adaptation. We further explored the spatiotemporal variations of EV and their potential socioeconomic impacts at the watershed scale. Our results show significant geospatial variations in future EV under the three scenarios, with the northern region of the upstream area being the most severely affected. Under the ecological conservation management scenario and historical trend scenario, the ecological environment of the basin improves, with a decrease in very high vulnerability areas by 4.45% and 3.08%, respectively, due to the protection and restoration of ecological land. Conversely, under the urban development and construction scenario, intensified climate change and increased land use artificialization exacerbate EV, with medium and high vulnerability areas increasing by 1.86% and 7.78%, respectively. The population in high and very high vulnerability areas is projected to constitute 32.75–33.68% and 34.59–39.21% of the YRB’s total population in 2040 and 2060, respectively, and may continue to grow. Overall, our scenario analysis effectively demonstrates the positive impact of ecological protection on reducing EV and the negative impact of urban expansion and economic development on increasing EV. Our work offers new insights into land resource allocation and the development of ecological restoration policies. Full article

In cloud-based Distributed Acoustic Sensing (DAS) sensor data management, we are confronted with two primary challenges. First, the development of efficient storage mechanisms capable of handling the enormous volume of data generated by these sensors poses a challenge. To solve this issue, we propose a method to address the issue of handling the large amount of data involved in DAS by designing and implementing a pipeline system to efficiently send the big data to DynamoDB in order to fully use the low latency of the DynamoDB data storage system for a benchmark DAS scheme for performing continuous monitoring over a 100 km range at a meter-scale spatial resolution. We employ the DynamoDB functionality of Amazon Web Services (AWS), which allows highly expandable storage capacity with latency of access of a few tens of milliseconds. The different stages of DAS data handling are performed in a pipeline, and the scheme is optimized for high overall throughput with reduced latency suitable for concurrent, real-time event extraction as well as the minimal storage of raw and intermediate data. In addition, the scalability of the DynamoDB-based data storage scheme is evaluated for linear and nonlinear variations of number of batches of access and a wide range of data sample sizes corresponding to sensing ranges of 1–110 km. The results show latencies of 40 ms per batch of access with low standard deviations of a few milliseconds, and latency per sample decreases for increasing the sample size, paving the way toward the development of scalable, cloud-based data storage services integrating additional post-processing for more precise feature extraction. The technique greatly simplifies DAS data handling in key application areas requiring continuous, large-scale measurement schemes. In addition, the processing of raw traces in a long-distance DAS for real-time monitoring requires the careful design of computational resources to guarantee requisite dynamic performance. Now, we will focus on the design of a system for the performance evaluation of cloud computing systems for diverse computations on DAS data. This system is aimed at unveiling valuable insights into performance metrics and operational efficiencies of computations on the data in the cloud, which will provide a deeper understanding of the system’s performance, identify potential bottlenecks, and suggest areas for improvement. To achieve this, we employ the CloudSim framework. The analysis reveals that the virtual machine (VM) performance decreases significantly the processing time with more capable VMs, influenced by Processing Elements (PEs) and Million Instructions Per Second (MIPS). The results also reflect that, although a larger number of computations is required as the fiber length increases, with the subsequent increase in processing time, the overall speed of computation is still suitable for continuous real-time monitoring. We also see that VMs with lower performance in terms of processing speed and number of CPUs have more inconsistent processing times compared to those with higher performance, while not incurring significantly higher prices. Additionally, the impact of VM parameters on computation time is explored, highlighting the importance of resource optimization in the DAS system design for efficient performance. The study also observes a notable trend in processing time, showing a significant decrease for every additional 50,000 columns processed as the length of the fiber increases. This finding underscores the efficiency gains achieved with larger computational loads, indicating improved system performance and capacity utilization as the DAS system processes more extensive datasets. Full article

This paper studies the role of resource orchestration in promoting business model innovation in servitization transformation enterprises to achieve sustainable development. Taking Sany Heavy Industry as the research focus, a three-level evaluation index is constructed to identify the resources and capabilities that have a key impact in the process. Through the continuous decomposition and integration of resources and capabilities, the resource orchestration behavior of business model innovation in the process of enterprise service transformation is obtained. The research results reveal the strategic evolution from “acquisition–stabilization–mobilization” to “accumulation–enrichment–coordination”, and finally to “accumulation–pioneering–deployment”, which plays an important role in redefining servitization value creation and transforming business model logic. This research helps to understand how resource orchestration promotes business model innovation in the context of servitization transformation to achieve the sustainable development of enterprises. Full article

The decline in the role of agriculture as the basis for the livelihood of rural residents has led to the development of new directions for rural transformation. In Poland, the concept of multifunctional development has gained the most popularity. However, it does not have a defined spatial development model. There has also been no research into how the development of non-agricultural functions affects spatial development and to what extent this development is sustainable. Therefore, the aim of this study is to show and compare the changes that have taken place over the last 40–50 years in the spatial arrangements of development in traditional agricultural villages and in villages with different non-agricultural functions (tourist, industrial, and service functions). At the same time, we want to indicate which of these functions have contributed to the development of the most sustainable spatial arrangements. To this end, we selected three indicators of sustainable development of rural space: compactness of buildings, continuation of traditional rural layouts, and availability of services, and then carried out an analysis of changes in these indicators on the basis of archival and current cartographic materials and data on service facilities. We conducted the research for four municipalities in eastern Poland (50 villages). The results indicate the predominance of negative spatial phenomena such as the deterioration of the accessibility of services and spatial development contrary to historical spatial layouts. There is a spillover of development in the form of discontinuous, chaotic clusters of buildings often having the character of suburbia and, consequently, the disappearance of village centres, worsening walkability, and blurring of village boundaries. The only positive change is an increase in the compactness of buildings—mainly in villages that previously had a dispersed character. It is difficult to identify village functions that would unequivocally favour spatial sustainability. The service villages showed slight advantages in terms of social (availability of services) and environmental (compactness of buildings) factors. In contrast, the development of agricultural villages was more favourable in cultural terms (traditional village layouts). In all aspects, negative changes were recorded in industrial villages and (the worst results) in tourist villages. However, the trends were similar in all municipalities, which draws attention primarily to the lack of a rational spatial policy related to multifunctional village development. Full article