The overhead power transmission line, as an important component of equipment for long-distance power transmission, is threatened by icing and galloping, which will lead to equipment troubles and ...cause huge economic loss. Thus, there is a great need for on-line monitoring for transmission lines. Because the photoelectric composite cable, such as optical fiber composite overhead ground wire (OPGW) is widely used, it is possible to introduce distributed optical fiber sensors (DOFS) into transmission line status monitoring. Common schemes based on DOFS usually offer low sensing density and are hard to realize global awareness, while phase sensitive optical time domain reflectometry (Φ-OTDR), as a DOFS that has the characteristic of distributed sensing, is hoping to address the limitation. In this paper, by establishing mathematical models, proposing analytical method, and building demonstration devices to analyze the dynamic strain characteristics of overhead power transmission line, an Φ-OTDR based on-line monitoring scheme of transmission line status is presented and experimentally proved for the first time. The estimation error of sag is less than 5.8% on centimeter scale, and the estimation error of ice thickness is no more than 10.84% on sub-millimeter scale, which gives an accurate description of transmission line status and provides strong support for early warning of transmission line failures.
Microplastics, which are tiny plastic particles less than 5 mm in diameter, are widely present in the environment, have become a serious threat to aquatic life and human health, potentially causing ...ecosystem disorders and health problems. The present study aimed to investigate the effects of microplastics, specifically microplastics-polystyrene (MPs-PS), on the structural integrity, gene expression related to tight junctions, and gut microbiota in mice. A total of 24 Kunming mice aged 30 days were randomly assigned into four groups: control male (CM), control female (CF), PS-exposed male (PSM), and PS-exposed female (PSF)(n = 6). There were significant differences in villus height, width, intestinal surface area, and villus height to crypt depth ratio (V/C) between the PS group and the control group(C) (p <0.05). Gene expression analysis demonstrated the downregulation of Claudin-1, Claudin-2, Claudin-15, and Occludin, in both duodenum and jejunum of the PS group (p < 0.05). Analysis of microbial species using 16S rRNA sequencing indicated decreased diversity in the PSF group, as well as reduced diversity in the PSM group at various taxonomic levels. Beta diversity analysis showed a significant difference in gut microbiota distribution between the PS-exposed and C groups (R2 = 0.113, p<0.01), with this difference being more pronounced among females exposed to MPs-PS. KEGG analysis revealed enrichment of differential microbiota mainly involved in seven signaling pathways, such as nucleotide metabolism(p<0.05). The relative abundance ratio of transcriptional pathways was significantly increased for the PSF group (p<0.01), while excretory system pathways were for PSM group(p<0.05). Overall findings suggest that MPs-PS exhibit a notable sex-dependent impact on mouse gut microbiota, with a stronger effect observed among females; reduced expression of tight junction genes may be associated with dysbiosis, particularly elevated levels of Prevotellaceae.
•A novel multiscale topology optimization method is proposed for designing asymmetric porous sandwich structures.•Multi-material sandwich structures are topologically optimized using the proposed ...method.•The thickness and material of two face sheets and the configuration of composite cores are simultaneously optimized.•Parametric level set method and alternating active-phase method are adopted.•Several 2D and 3D numerical examples are investigated and compared.
Compared with conventional symmetric sandwich structure with identical face sheets and single-material core, asymmetric porous sandwich structures (APSSs), which are composed of unidentical face sheets and composite core, usually take better advantage of all materials and provide superior bending stiffness. However, current studies regarding the APSSs are mainly analytical- and experimental-based methods with predefined face sheet thicknesses and core configurations, which greatly confines the potential loading capacity of sandwich structures. This paper develops a multiscale topology optimization method for the multi-material APSSs, which can realize the designs of the thickness and material of two face sheets at macroscale as well as the configuration of composite cores at microscale for minimizing structural compliance. Firstly, at macroscale, a multi-material variable thickness sheet method integrated with an alternating active-phase algorithm are employed to optimize the thickness and material of two solid face sheets. Then, at microscale, a difference-set-based multi-material level set (DS-MMLS) model is applied to represent the topology of each material phase within sandwich core, and their topological evolution can be readily achieved by using a parametric level set method also combined with the alternating active phase algorithm. Several 2D and 3D numerical examples are provided to show the effectiveness and advantages of the proposed method. The results indicate that compliances of the optimized APSSs show superior advantages over some conventional sandwich structures with predefined design features.
•The first and second derivatives for the transient response of non-viscously damped systems are calculated.•The direct differentiate method is adopted.•The sensitivities are derived by using a ...modified precise integration method.•The computational considerations of the methods are investigated and compared.•Two numerical examples are given to show the performances of the method.
Calculation of the first and second derivatives of transient response with respect to design variables is a prerequisite when gradient-based methods are adopted for optimization design in time-domain. In this paper, a design sensitivity analysis (DSA) method for calculating the first and second derivatives of the transient response for non-viscously damped systems is developed. The assumed damping forces depend on the past history of motion via convolution integrals over some kernel functions. The direct differentiate method (DDM) is selected to derive the DSA method. By introducing a generalized damping model in expression of fraction formula, the equations of motion of the non-viscously damped system are transformed into a state-space form without the convolution integral terms. Then, the first and second derivatives of the transient response are formulated based on a modified precise integration method using the DDM. The numerical stability, accuracy and implementation effort of the DDM are discussed. Two numerical examples are comparatively demonstrated using the DDM, the discretize-then-differentiate adjoint variable method (AVM) and the differentiate-then-discretize AVM. The results indicate that, by considering all the computational considerations, the proposed DDM is more suitable than the other two methods for the sensitivity analysis of transient response for non-viscously damped systems. Besides, it is also the only existing method to capture the second-order derivatives of transient response for the non-viscously damped systems.
In this paper, by considering higher-order effects of residual attachment modes, a new free-interface component mode synthesis (CMS) method is developed for non-classically damped systems. Firstly, ...based on the Neumann expansion, the higher-order effects of the residual attachment modes are accurately expressed by the available lower-order modes and the system matrices. Secondly, by using the residual attachment modes and complex modes, the non-classically damped subcomponents are reduced and assembled in the physical space instead of the frequently-used state-space. Then, the new free-interface CMS method is derived and solved built on a frequency shifting technique and an iteration method. Finally, the performances of the presented method are illustrated by two numerical examples and compared with other first- and second-order approximated CMS methods. The results indicate that the presented CMS method for the non-classically damped systems is more accurate than other methods and suitable for the case when both high- and low-order modes are truncated.
•A new CMS method for non-classically damped system is presented.•The CMS method considers the higher-order effects of residual attachment modes.•Residual attachment modes are derived explicitly by lower-order modes and system matrices.•Subcomponents are assembled in physical space instead of state-space.•The proposed method is applicable to the case when both low- and high-order modes are truncated.
Stomata are two-celled valves that control epidermal pores whose spacing optimizes shoot-atmosphere gas exchange. They develop from protodermal cells after unequal divisions followed by an equal ...division and differentiation. The concentration of the hormone auxin, a master plant developmental regulator, is tightly controlled in time and space, but its role, if any, in stomatal formation is obscure. Here dynamic changes of auxin activity during stomatal development are monitored using auxin input (DII-VENUS) and output (DR5:VENUS) markers by time-lapse imaging. A decrease in auxin levels in the smaller daughter cell after unequal division presages the acquisition of a guard mother cell fate whose equal division produces the two guard cells. Thus, stomatal patterning requires auxin pathway control of stem cell compartment size, as well as auxin depletion that triggers a developmental switch from unequal to equal division.
The breast cancer stem cells contribute to the initiation, progression, recurrence, metastasis as well as resistance of breast cancer. However, the mechanisms underlying the maintenance of breast ...cancer stemness have not been fully understood.
TCGA and GEO data were used for measuring miR-520b expression in breast cancer tissues. Kaplan-meier analysis was used for determining the relationship between miR-520b expression level and the prognosis of patients. Genetic manipulation was performed by lentivirus system and miR-520b inhibitor was used for knockdown of miR-520b. qRT-PCR and Western blot were employed to determine the mRNA and protein levels, respectively. The stemness and EMT (Epithelial to mesenchymal transition) were assessed by sphere-formation and transwell assay as well as the expression of the related markers. The target genes of miR-520b were identified using the online database starBase V3.0.
miR-520b is upregulated in cancer tissues of breast cancer patients and predicts poor prognosis. Upregulation of miR-520b was found in breast cancer stem cells. Ectopic expression of miR-520b promotes the stemness of the breast cancer cells, conversely, depletion of miR-520b attenuates the stemness of these cells. miR-520b positively regulates Hippo/YAP signaling pathway and overexpression of LAST2 abolished the effect of miR-520b on the stemness of breast cancer cells.
miR-520b promotes the stemness of breast cancer patients by activating Hippo/YAP signaling via targeting LATS2.
Toward the long-standing dream of artificial intelligence, two successful solution paths have been paved: 1) neuromorphic computing and 2) deep learning. Recently, they tend to interact for ...simultaneously achieving biological plausibility and powerful accuracy. However, models from these two domains have to run on distinct substrates, i.e., neuromorphic platforms and deep learning accelerators, respectively. This architectural incompatibility greatly compromises the modeling flexibility and hinders promising interdisciplinary research. To address this issue, we build a unified model description framework and a unified processing architecture (Tianjic), which covers the full stack from software to hardware. By implementing a set of integration and transformation operations, Tianjic is able to support spiking neural networks, biological dynamic neural networks, multilayered perceptron, convolutional neural networks, recurrent neural networks, and so on. A compatible routing infrastructure enables homogeneous and heterogeneous scalability on a decentralized many-core network. Several optimization methods are incorporated, such as resource and data sharing, near-memory processing, compute/access skipping, and intra-/inter-core pipeline, to improve performance and efficiency. We further design streaming mapping schemes for efficient network deployment with a flexible tradeoff between execution throughput and resource overhead. A 28-nm prototype chip is fabricated with >610-GB/s internal memory bandwidth. A variety of benchmarks are evaluated and compared with GPUs and several existing specialized platforms. In summary, the fully unfolded mapping can achieve significantly higher throughput and power efficiency; the semi-folded mapping can save 30x resources while still presenting comparable performance on average. Finally, two hybrid-paradigm examples, a multimodal unmanned bicycle and a hybrid neural network, are demonstrated to show the potential of our unified architecture. This article paves a new way to explore neural computing.
River‐dominated marginal seas are important carbon sinks on Earth. However, their carbon sequestration capacities are changing due to increased anthropogenic perturbations. Herein, we employ ...substantial datasets to study the characteristics of organic carbon (OC) from the East China Sea (ECS) in 2006 and 2018 and reveal the impacts of reservoir construction on the OC deposition in this region. We show that the distribution of sedimentary OC in the ECS is primarily controlled by riverine input and seabed erosion processes. Hydrodynamic processes influence the OC deposition due to both the scouring of fine‐grained sediments and selective degradation of OC associated with the sediment mobilization. The deposition flux of OC in the ECS decreased by 48% after reservoir construction. These findings demonstrate that reservoir construction seriously affected the OC deposition in the ECS and may be applicable to river‐dominated continental shelves worldwide.
Key Points
Reservoir construction changed the transport process and deposition pattern of organic carbon in the East China Sea
The deposition flux of organic carbon in the East China Sea decreased by 48% due to reservoir construction
Deposition flux reduction threatens river‐dominated margins worldwide and should be taken seriously
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