Fatigue Life Simulation and Analysis of Aluminum Alloy Sheet Self-piercing Riveting

The fatigue life prediction model of self-piecing riveting components of aluminum alloy is established and the effects of roughness and residual stress on fatigue life of self-piercing riveting components is analyzed by the model. Finite element software ABAQUS and fatigue analysis software FE-SAFE are used to study the effects of roughness and residual stress on the fatigue life of self-piecing riveting components through finite element simulation and mathematical statistics multivariate orthogonal regression experiment. The quantitative relations between fatigue life and three variables (roughness, residual stress and maximum stress) are fitted, and the variation trend of fatigue life with roughness and residual stress is obtained. The order of influence of roughness, residual stress, maximum stress and two interactions on fatigue life is as follows: residual stress, interaction between roughness and residual stress, roughness. When the maximum stress is fixed, the fatigue life decreases with the increase of roughness with a certain residual stress, and the fatigue life decreases with the increase of roughness with a certain residual stress. The average error between the fatigue experiment results and the simulation results is 9.74%, which proves that the simulation results are reliable

Buddhist monasteries facilitated landscape conservation on the Qinghai-Tibetan Plateau

Context: The Sanjiangyuan region of the Qinghai-Tibetan Plateau—also known as the “Three Rivers’ Headwaters”—is the origin of the Yellow, Yangtze, and Mekong Rivers and therefore the key water source for hundreds of millions of downstream residents. Protecting this region’s ecosystems is a key priority for sustainable development in China and Asia. An important social dimension of Sanjiangyuan is the long-established and widespread presence of Tibetan Buddhism, particularly as manifested in the large number of monasteries throughout the region. However, the influence of cultural factors on environmental change remains largely understudied here. / Objective: We focus on two types of spatial associations—point-point and point-area features—to quantitatively investigate the effects of Buddhist monasteries on land use/cover change (LUCC) in surrounding landscapes. / Methods: We conduct a spatially-explicit analysis of Sanjiangyuan for two periods, 1990–2000 and 2010–2015, to identify and quantify the influence of the presence and spatial distributions of Buddhist monasteries on LUCC compared to village communities that lack monasteries. / Results: We found that the presence of monasteries is highly correlated with the preservation of natural ecosystems, specifically of grasslands and forests. Within monastery buffer zones with radii between 1 and 10 km, 7.13–9.30% more grassland area and 7.14–7.47% more forest area remained around monasteries compared to villages. This contrast decreased with increasing distance to the monastery/village. Overall, built-up areas were also much smaller around monasteries than around villages, while unused land was more commonly transformed to forests and grasslands around monasteries. / Conclusions: These findings strongly support the idea that Buddhist culture, as manifested through its physical institutions and communities, are instrumental in achieving desired landscape conservation outcomes

Testing the Hypothesis of Multiple Origins of Holoparasitism in Orobanchaceae: Phylogenetic Evidence from the Last Two Unplaced Holoparasitic Genera, Gleadovia and Phacellanthus

Orobanchaceae is the largest family among the parasitic angiosperms. It comprises non-parasites, hemi- and holoparasites, making this family an ideal test case for studying the evolution of parasitism. Previous phylogenetic analyses showed that holoparasitism had arisen at least three times from the hemiparasitic taxa in Orobanchaceae. Until now, however, not all known genera of Orobanchaceae were investigated in detail. Among them, the unknown phylogenetic positions of the holoparasites Gleadovia and Phacellanthus are the key to testing how many times holoparasitism evolved. Here, we provide clear evidence for the first time that they are members of the tribe Orobancheae, using sequence data from multiple loci (nuclear genes ITS, PHYA, PHYB, and plastid genes rps2, matK). Gleadovia is an independent lineage whereas Phacellanthus should be merged into genus Orobanche section Orobanche. Our results unambiguously support the hypothesis that there are only three origins of holoparasitism in Orobanchaceae. Divergence dating reveals for the first time that the three origins of holoparasitism were not synchronous. Our findings suggest that holoparasitism can persist in specific clades for a long time and holoparasitism may evolve independently as an adaptation to certain hosts

Roadmap on printable electronic materials for next-generation sensors

The dissemination of sensors is key to realizing a sustainable, ‘intelligent’ world, where everyday objects and environments are equipped with sensing capabilities to advance the sustainability and quality of our lives—e.g., via smart homes, smart cities, smart healthcare, smart logistics, Industry 4.0, and precision agriculture. The realization of the full potential of these applications critically depends on the availability of easy-to-make, low-cost sensor technologies. Sensors based on printable electronic materials offer the ideal platform: they can be fabricated through simple methods (e.g., printing and coating) and are compatible with high-throughput roll-to-roll processing. Moreover, printable electronic materials often allow the fabrication of sensors on flexible/stretchable/biodegradable substrates, thereby enabling the deployment of sensors in unconventional settings. Fulfilling the promise of printable electronic materials for sensing will require materials and device innovations to enhance their ability to transduce external stimuli—light, ionizing radiation, pressure, strain, force, temperature, gas, vapours, humidity, and other chemical and biological analytes. This Roadmap brings together the viewpoints of experts in various printable sensing materials—and devices thereof—to provide insights into the status and outlook of the field. Alongside recent materials and device innovations, the roadmap discusses the key outstanding challenges pertaining to each printable sensing technology. Finally, the Roadmap points to promising directions to overcome these challenges and thus enable ubiquitous sensing for a sustainable, ‘intelligent’ world

Review on active building energy conservation using phase change materials

With a increasing application of phase change energy storage technology in the fields of building energy conservation, refrigeration, and air conditioning, the shortcomings of traditional phase change materials (PCMs) have become important, which seriously restricts the development of phase change cold storage technology. Therefore, the new phase change materials have become a research focus in the field of phase change energy storage. The classification and characteristics of phase change materials are briefly described in the paper. In addition, the active building energy-saving are reviewed

Hydrogen Evolution upon Ammonia Borane Solvolysis: Comparison between the Hydrolysis and Methanolysis Reactions

Hydrogen (H2) production is a key challenge for green carbon-free sustainable energy. Among the H2 evolution methods from H-rich materials, ammonia borane (AB) solvolysis stands as a privileged source under ambient and sub-ambient conditions given its stability, non-toxicity, and solubility in protic solvents, provided suitable and optimized nanocatalysts are used. In this paper dedicated to Prof. Avelino Corma, we comparatively review AB hydrolysis and alcoholysis (mostly methanolysis) in terms of nanocatalyst performances and discuss the advantages and inconveniences of these two AB solvolysis methods including AB regeneration

Key technologies and future development trends of intelligent earth–rock dam construction

The rapid advancement of information technologies, such as cloud computing, internet of things (IoT), and big data, has significantly enhanced the intelligence level in dam construction. Intelligent monitoring systems for dam filling have garnered considerable attention from water conservancy and hydropower engineering units, owing to their capability for refined management and quality control of layered and compartmentalized construction processes. The construction of earth–rock dams has undergone a transformation, shifting from manual management of dam compaction equipment, layer management, and quality control to a comprehensive intelligent approach. This new approach encompasses fine-grained control of unit engineering, dam material identification, unmanned driving technology, real-time assessment and monitoring of compaction quality, and early warning forecasting. This article presents a systematic overview of key technologies employed in the intelligent construction process of earth–rock dams. These technologies include the fine decomposition of building information modeling (BIM) models on web platforms, rapid identification of dam material particle size, the application of autonomous driving technology for intelligent dam filling, and real-time monitoring and evaluation of dam compaction characteristics. Additionally, the paper discusses the latest research results in the field, building upon existing technology progress, and concludes by exploring the future development trends of intelligent dam construction. The construction of intelligent earth–rock dams serve as a crucial reference and valuable lessons for the development and construction of high earth–rock dam projects.</p

RESEARCH ON POST-PROCESSING METHOD OF CONTINUUM STRUCTURE TOPOLOGY OPTIMIZATION BASED ON VARIABLE DENSITY METHOD

The variable density method has become an effective method to solve the topology optimization problem of continuum structure due to its advantages such as few design variables and high efficiency. Aiming at the problem of the gray unit and sawtooth boundary in the optimization process of the variable density method, a post-processing method of variable density method for continuum topology optimization is proposed in this paper. The topology optimization model is binarized and the sawtooth shape boundary line is extracted, and the target discrete corner point set is obtained, used as the sample point for curve fitting to obtain the optimized structure with smooth boundary. Experimental results show that this method effectively avoids the zigzag boundary and intermediate density of the optimization result, and improves the manufacturability of the optimization result under the premise of ensuring that the structural performance is within the allowable range

Analysis of influence of energy storage system parameters on HVDC commutation failure overvoltage

Overvoltage is a common fault in high voltage direct current (HVDC) transmission systems, which directly affects the safe and stable operation of the system. Energy storage system has been widely used in power system because of its fast response speed, high precision and bidirectional energy transmission. As a variable parameter, the low voltage traverse active power coefficient directly affects the overvoltage of commutation failure in HVDC system. In this paper, the influence of transient characteristics and energy storage parameters on commutation failure overvoltage of energy storage system connected to HVDC is analyzed. Based on PSASP simulation, combined with the actual characteristic setting parameters of a power grid in northwest China, the positive correlation between energy storage low-pass active power and transient overvoltage of HVDC system commutating failure is verified by dynamic trajectory sensitivity analysis, and the optimization space of HVDC energy storage system is expanded