| 1. |
- Zhang, Qiyue, et al.
(författare)
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Integrated CFD and MBD methods for dynamic performance analysis of a high-speed train transitioning through varied windbreak corridor designs
- 2024
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - 0167-6105. ; 250
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Tidskriftsartikel (refereegranskat)abstract
- With increasing train speeds, the wind environment along routes has become complex, variable, and extreme. Constructing windbreak facilities is an effective strategy to enhance train operational safety in windy zones. Various windbreak designs exhibit notable differences in improving train dynamic performance, and economic considerations are also crucial. Utilizing the non-constant compressible Reynolds time-averaged equation URANS (Unsteady Reynold-averaged Navier–Stokes) alongside the shear-stress transport (SST) k-ω turbulence model, this study simulates the non-constant aerodynamic characteristics of a 350 km/h high-speed train traversing through different forms of windbreak corridors in a 30 m/s wind zone. The train's dynamic response was captured using a combined CFD–MBD (Computational Fluid Dynamics and Multi-Body Dynamics) offline time-domain simulation, the accuracy of which was verified experimentally. Results indicate that vortices of various positions and shapes form in the flow field along the windbreak corridor depending on the size of the openings. Using the no-windbreak corridor (Case 1) and the fully enclosed corridor (Case 4) as control groups, it was observed that smaller openings lead to more stable airflow, enhancing peak damping and fluctuation effects, albeit with varying stages of aerodynamic load fluctuation. The 1/3-opening windbreak corridor (Case 3) effectively mitigated the sudden aerodynamic load changes at the wind zone transition of the 2/3-opening windbreak corridor (Case 2), with the primary fluctuation area in Case 3 being the wind section. Dynamic analyses revealed that Case 2 exhibited insufficient lateral aerodynamic performance, raising derailment concerns. In contrast, Case 3 ensured travel safety and comfort effectively, while Case 4 offered excessive protective capacity. This study's findings serve as a valuable reference for designing windbreak corridors and ensuring the safe operation of trains in windy regions.
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| 2. |
- Chen, Zheng wei, et al.
(författare)
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Reducing the aerodynamic drag of high-speed trains by air blowing from the nose part: Effect of blowing speed
- 2023
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - 0167-6105. ; 238
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Tidskriftsartikel (refereegranskat)abstract
- To reduce the aerodynamic drag of high-speed trains, this work proposes an air blowing configuration on the head and tail cars of high-speed trains. The variation in the aerodynamic drag and slipstream velocity is analyzed under different blowing velocities, and the flow mechanism for train aerodynamic performance alteration is explained. The results show that under the blowing speeds of Ub = 0.05Ut, 0.10Ut, 0.15Ut, and 0.20Ut, where Ut is the train speed, the total drag coefficient (Cd) decreases by 5.81%, 10.78%, 13.70%, and 15.43% compared to the without-blowing case, respectively. However, with the increase in the blowing speed, the reduction trend of Cd tends to be smoother; namely, the decrement ratio compared to the previous blowing speed for the head car is 9.08%, 0.11%, 0.60%, and 1.14% for Ub = 0.05Ut, 0.10Ut, 0.15Ut, and 0.20Ut, respectively. The blowing measure generates an air gap between the coming flow and train surface, consequently causing a reduction in the viscous and pressure drag. In addition, the structure size and strength of the wake flow under different blowing cases show a decreasing trend from Ub = 0.00Ut to 0.10Ut and then an increasing trend from Ub = 0.10Ut to 0.20Ut. Thus, considering the blowing cost, efficiency, and flow structure evolution comprehensively, the case of Ub = 0.10Ut is recommended. Under this blowing speed, the reduction ratio of the aerodynamic drag is 9.18%, 12.77%, 10.90%, and 10.78% for the head, middle, tail car, and total train, respectively.
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| 3. |
- Greco, Rossella, et al.
(författare)
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Activation of 2D cobalt hydroxide with 0D cobalt oxide decoration for microplastics degradation and hydrogen evolution
- 2023
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Ingår i: Chemical Engineering Journal. - 1385-8947. ; 471
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Tidskriftsartikel (refereegranskat)abstract
- The 2D semiconductors are important players in environmental and energy fields due to their unique catalytic and physical properties defined by their dimensionality. Versatile functionalities on one 2D matrix will enlarge its application scopes but require dedicated engineering paths. In this work, we present a cross-dimensional strategy by decorating 0D Co3O4 onto 2D Co(OH)2 to form a multifunctional photocatalyst. The one-pot hydrothermally synthesized Co3O4@Co(OH)2 composite is capable of degrading polystyrene microplastics with an efficiency of 40% under 0.495 W white LED illumination. In a separated experiment, H2 evolution reaction from water splitting was evaluated in absence of sacrificial agents leading to 43 μmol g−1 and to an apparent quantum efficiency of 3.48% at 420 nm. The study of the energy band diagrams by UV–Visible and ambient photoemission spectroscopy and the analysis of the radicals involved in the reaction of photocatalytic degradation allow to unveil the mechanisms for both the processes herein studied. Finally, we could confirm that the heterostructure benefits the redox potentials of 2D and 0D counterparts and facile electron transfers when crossing two different dimensions. These results provide guidelines and inspiration for cross-dimensional activations of low-dimensional materials for versatile functionalities.
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| 4. |
- Luo, Yifei, et al.
(författare)
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Technology Roadmap for Flexible Sensors
- 2023
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Ingår i: ACS Nano. - : American Chemical Society. - 1936-0851 .- 1936-086X. ; 17:6, s. 5211-5295
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Forskningsöversikt (refereegranskat)abstract
- Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.
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| 5. |
- Niu, Caoping, et al.
(författare)
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Configuration stability and physical properties of new diamondene structure
- 2023
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Ingår i: Materials Today Communications. - : Elsevier BV. - 2352-4928. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- The structure of monolayer diamond or diamondene based on bi-layer graphene through pressure conversion, combining characteristics of both graphene and diamond, has been confirmed theoretically and experimentally. In this work, by extending diamondene structure to the minimum repeating unit of bulk diamond along different crystallographic orientations, the configuration stability and physical properties of 21 kinds of diamondene were systematically investigated based on first-principles methods, and effects of hydrogen saturation were also presented. It was found that diamondene formed by compressing layered graphene would graphitize, and surface termination could prevent the graphitization. The electronic properties of diamondene can be adjusted by the concentration of H atoms with the bandgap varying from 0 eV to 3.45 eV, and some configurations exhibit ferromagnetism or anti-ferromagnetism. Moreover, diamondene has a high Young's modulus comparable to bulk diamond. Particularly, the configuration containing dumbbell units is twice as hard as diamond. The formation energies of all stable diamondene configurations were illustrated, and it was found that it is easier to synthesize diamondene by compressing few-layer graphene. Furthermore, the instability law of two-dimensional carbon structure was systematically discussed, which is important for designing new carbon allotropes.
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| 6. |
- Talebi, Parisa, et al.
(författare)
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Spectromicroscopic determinations of chemical environments of Ni in MoS2-Ag-Ni ternary systems
- 2023
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Ingår i: X-Ray Spectrometry. - : Wiley. - 0049-8246 .- 1097-4539. ; 52:1, s. 38-45
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Tidskriftsartikel (refereegranskat)abstract
- Using heterogeneous photocatalysts for harvesting sunlight and converting it for water remediation and splitting are promising to mitigate the possible crisis of environment and energy. Among various composites, the MoS2-based heterostructures and Ni-based systems exhibit unique electronic, optical properties and redox capabilities, enabling their roles as photocatalysts. Herein, the impacts of chemical environments on the Ni electronic structures within the MoS2-Ag-Ni ternary systems are studied via X-ray photoemission electron spectroscopy (X-PEEM). Ni nanoparticles with two different sizes of 70 and 200 nm were loaded to MoS2 flakes with silver buffers as bridges. Heterostructures with a nominal mol percentage of (MoS2)77Ag3.7Ni19.3 were synthesized through an ultrasound-assisted wet method. The oxidation states and various interfacial interactions of Ni with MoS2 in MoS2-Ag-Ni ternary composite are spectromicroscopically determined, combining the X-ray absorption spectroscopy near Ni L-edges and the imaging capability of the X-PEEM. Results showed that Ni mainly retrains its chemical states of metal and native oxidizations without observable electronic features subjected to bonding with the sulfur from the MoS2 flakes. The charge migration channel set up by the Ag buffer thus contributes to electron–hole migrations that facilitate the photocatalytic performance of the ternary system eventually.
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| 7. |
- Zhang, Lixiu, et al.
(författare)
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Advances in the Application of Perovskite Materials
- 2023
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Ingår i: NANO-MICRO LETTERS. - : SHANGHAI JIAO TONG UNIV PRESS. - 2311-6706. ; 15:1
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Forskningsöversikt (refereegranskat)abstract
- Nowadays, the soar of photovoltaic performance of perovskite solar cells has set off a fever in the study of metal halide perovskite materials. The excellent optoelectronic properties and defect tolerance feature allow metal halide perovskite to be employed in a wide variety of applications. This article provides a holistic review over the current progress and future prospects of metal halide perovskite materials in representative promising applications, including traditional optoelectronic devices (solar cells, light-emitting diodes, photodetectors, lasers), and cutting-edge technologies in terms of neuromorphic devices (artificial synapses and memristors) and pressure-induced emission. This review highlights the fundamentals, the current progress and the remaining challenges for each application, aiming to provide a comprehensive overview of the development status and a navigation of future research for metal halide perovskite materials and devices.
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| 8. |
- Borthakur, Dulal, et al.
(författare)
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Current status and trends in forest genomics
- 2022
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Ingår i: Forestry Research. - : Maximum Academic Press. - 2767-3812. ; 2
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Forskningsöversikt (refereegranskat)abstract
- Forests are not only the most predominant of the Earth's terrestrial ecosystems, but are also the core supply for essential products for human use. However, global climate change and ongoing population explosion severely threatens the health of the forest ecosystem and aggravtes the deforestation and forest degradation. Forest genomics has great potential of increasing forest productivity and adaptation to the changing climate. In the last two decades, the field of forest genomics has advanced quickly owing to the advent of multiple high-throughput sequencing technologies, single cell RNA-seq, clustered regularly interspaced short palindromic repeats (CRISPR)-mediated genome editing, and spatial transcriptomes, as well as bioinformatics analysis technologies, which have led to the generation of multidimensional, multilayered, and spatiotemporal gene expression data. These technologies, together with basic technologies routinely used in plant biotechnology, enable us to tackle many important or unique issues in forest biology, and provide a panoramic view and an integrative elucidation of molecular regulatory mechanisms underlying phenotypic changes and variations. In this review, we recapitulated the advancement and current status of 12 research branches of forest genomics, and then provided future research directions and focuses for each area. Evidently, a shift from simple biotechnology-based research to advanced and integrative genomics research, and a setup for investigation and interpretation of many spatiotemporal development and differentiation issues in forest genomics have just begun to emerge.
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| 9. |
- Niu, Jiqiang, et al.
(författare)
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Aerodynamic simulation of effects of one- and two-side windbreak walls on a moving train running on a double track railway line subjected to strong crosswind
- 2022
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 221
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Tidskriftsartikel (refereegranskat)abstract
- High-speed railway lines are widely distributed worldwide. The surrounding wind environment of such railway lines is complex, which significantly affects the safety of high-speed train operations. Using a combination of the computational fluid dynamics method of improved delayed detached eddy simulation and sliding grid technology, the effects of one- and two-side windbreak walls on the unsteady aerodynamic performance of a high-speed train running under a crosswind on a double-track railway line with an embankment and the flow-field characteristics around the train were systematically studied. The grid independence and numerical methods used in this study were verified. The results showed that when the windbreak wall was absent, the aerodynamic performance of the train running on the upstream railway line was the poorest, while the train running on the downstream railway line exhibited large aerodynamic fluctuations. The windbreak wall significantly reduced the aerodynamic force and its fluctuation; the one- and two-side windbreak walls had different effects on the unsteady aerodynamic performance of trains running on the upstream and downstream railway lines under a crosswind. The one-side windbreak wall could restrain the aerodynamic fluctuation of the train more and is thus preferred from the perspective of construction effort and cost.
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| 10. |
- Niu, Shihui, et al.
(författare)
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p The Chinese pine genome and methylome unveil key features of conifer evolution
- 2022
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Ingår i: Cell. - : Elsevier BV. - 0092-8674 .- 1097-4172. ; 185:1, s. 204-
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Tidskriftsartikel (refereegranskat)abstract
- Conifers dominate the world's forest ecosystems and are the most widely planted tree species. Their giant and complex genomes present great challenges for assembling a complete reference genome for evolutionary and genomic studies. We present a 25.4-Gb chromosome-level assembly of Chinese pine (Pinus tabuliformis) and revealed that its genome size is mostly attributable to huge intergenic regions and long introns with high transposable element (TE) content. Large genes with long introns exhibited higher expressions levels. Despite a lack of recent whole-genome duplication, 91.2% of genes were duplicated through dispersed duplication, and expanded gene families are mainly related to stress responses, which may underpin conifers' adaptation, particularly in cold and/or arid conditions. The reproductive regulation network is distinct compared with angiosperms. Slow removal of TEs with high-level methylation may have contributed to genomic expansion. This study provides insights into conifer evolution and resources for advancing research on conifer adaptation and development.
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