At micro/nano scale, the stiffening effect and flexoelectric effect of strain gradient play important roles in the electromechanical coupling response of piezoelectric micro-components. In this ...paper, the large deflection bending problem of circular piezoelectric micro-actuator is studied based on the extended linear dielectric theory. In addition to the piezoelectric effect, the flexoelectric effect, the stiffening effect of strain gradient and the high-order electric field effect of polarization gradient are introduced. According to the variational principle, a size-dependent model of circular piezoelectric micro-actuator is established to investigate its electromechanical coupling response. The contributions of piezoelectric effect and flexoelectric effect on large deflection behaviors of piezoelectric micro-actuator are revealed. It is hoped that the research results will be helpful to further understand the electromechanical coupling properties of piezoelectric micro-components and improve the control precision of piezoelectric micro-actuator.
Abstract
Flexoelectricity will dominate the electromechanical coupling of intelligent components in MEMS/NEMS due to its size-dependency. This paper focuses on investigating the flexoelectric ...responses of intelligent components of the circular plate type, which are commonly used in MEMS/NEMS. Utilizing Hamilton’s principle, the nonlinear flexoelectric circular plate model is presented by combining von Kármán plate theory and flexoelectric theory. The equilibrium equations and all boundary conditions are obtained and then discretized. The nonlinear static bending of the simply supported axisymmetric flexoelectric circular plate is investigated by combining DQM and iteration method. The distributions of dimensionless bending deflection and electric potential are analyzed under different loads. Moreover, the nonlinear free vibration behaviors are also investigated by combining the Galerkin method and Lindstedt–Poincaré Method. The flexoelectric effect and stiffening effect of strain gradient are revealed. This paper will be helpful to promote the application of flexoelectric intelligent components of the circular plate type, which are encountered commonly in engineering.
Increasing evidence showed that long noncoding RNAs (lncRNAs) played an important role in the occurrence and development of tumors. To date, lncRNA small nucleolar RNA host gene 12 (SNHG12) has ...revealed an oncogenic role in various tumors. However, the role of SNHG12 in cervical cancer is still unclear. Therefore, we focused on the biological function and molecular mechanism of SNHG12 in the tumorigenesis of cervical cancer. In this study, the expression of miR‐125b was observably downregulated in cervical cancer cells. Meanwhile, the expression of SNHG12 was obviously upregulated in cervical cancer cell lines (HeLa, SiHa, Caski, C4‐1, and C33A) compared with the immortalized cervical epithelial cells. The further assay showed that miR‐125b was a target of SNHG12 in cervical cancer. Moreover, a negative relationship between miR‐125b and SNHG12 was found in cervical cancer. In addition, SNHG12 inhibition restrained the proliferation, migration, and invasion of cervical cancer cells. Meanwhile, miR‐125b mimics repressed the expression of signal transducer and activator of transcription 3 (STAT3). The further assay showed that STAT3 was a target of miR‐125b in cervical cancer. In addition, sh‐STAT3 repressed the migration and invasion of cervical cancer cells. Furthermore, it showed that miR‐125b inhibitors reversed STAT3 expression restrained by the reduction of SNHG12 expression. In general, SNHG12 modulated STAT3 by sponging miR‐125b in cervical cancer and played an important role in the development of cervical cancer.
“Small nucleolar RNA host gene 12 (SNHG12) might be a novel biomarker for the diagnosis or treatment of cervical cancer and SNHG12/miR‐125b/ signal transducer and activator of transcription 3 axis was implicated in the progression of cervical cancer.”
Graphene quantum dots (GQDs) have attracted tremendous research interest due to the unique properties associated with both graphene and quantum dots. Here, a new application of GQDs as ideal ...electrode materials for supercapacitors is reported. To this end, a GQDs//GQDs symmetric micro‐supercapacitor is prepared using a simple electro‐deposition approach, and its electrochemical properties in aqueous electrolyte and ionic liquid electrolyte are systematically investigated. The results show that the as‐made GQDs micro‐supercapacitor has superior rate capability up to 1000 V s−1, excellent power response with very short relaxation time constant (τ0 = 103.6 μs in aqueous electrolyte and τ0 = 53.8 μs in ionic liquid electrolyte), and excellent cycle stability. Additionally, another GQDs//MnO2 asymmetric supercapacitor is also built using MnO2 nanoneedles as the positive electrode and GQDs as the negative electrode in aqueous electrolyte. Its specific capacitance and energy density are both two times higher than those of GQDs//GQDs symmetric micro‐supercapacitor in the same electrolyte. The results presented here may pave the way for a new promising application of GQDs in micropower suppliers and microenergy storage devices.
Graphene quantum dots (GQDs)‐based micro‐supercapacitors are prepared using a simple eletrodeposition approach and their electrochemical properties in aqueous and ionic liquid electrolytes are studied. The GQDs‐based micro‐supercapacitors exhibit superior rate capability, high power response capability, and excellent cyclic stability
Osteoarthritis (OA) is a long‐term and inflammatory disorder featured by cartilage erosion. Here, we describe nomilin (NOM), a triterpenoid with inflammation modulatory properties in variety of ...disorders. In this study, we demonstrated the latent mechanism of NOM in alleviating the progress of OA both in vitro and in vivo studies. The results showed that NOM pre‐treatment suppressed the IL‐1β–induced over‐regulation of pro‐inflammation factors, such as NO, IL‐6, PGE2, iNOS, TNF‐α and COX‐2. Moreover, NOM also down‐regulates the degradation of ECM induced by IL‐1β. Mechanistically, the NOM suppressed NF‐κB signalling via disassociation of Keap1‐Nrf2 in chondrocytes. Furthermore, NOM delays the disease progression in the mouse OA model. To sum up, this research indicated NOM possessed a new potential therapeutic option in osteoarthritis.
When backpropagation neural network (BPNN) is often applied to supervised classification, problems arise, including a slow convergence rate, local extremum, and difficulty in determining the number ...of hidden layers and hidden nodes that affect the classification accuracy and efficiency. These problems can be overcome by using smarter network designs. Adaptive boosting (AdaBoost), which combines multiple weak classifiers to create a strong classifier, has a strong classification advantage. In this article, we propose an acoustic seabed classification method that combines AdaBoost with the particle swarm optimization (PSO). The PSO-BP-AdaBoost algorithm uses multibeam echosounder backscatter data to solve the multiclassification problem of diverse seafloor sediment types with small differences between types. We optimize a BPNN using the PSO algorithm to obtain the optimal initial weight and threshold and combine these to form an AdaBoost strong classifier. The input data is obtained from the sonar mosaic from multibeam echosounder backscatter data collected in Jiaozhou Bay using a series of fine processing techniques. These processing techniques result in 34-dimensional (34-D) features using ReliefF analysis. The most advantageous 8-D features are used as input into the AdaBoost algorithm based on one-level decision tree, PSO-BP algorithm, support vector machine (SVM), and PSO-BP-AdaBoost algorithm. The PSO-BP-AdaBoost classification model has better classification accuracy. The overall accuracy is improved by 12.68%, 6.78%, and 3.56%, respectively, which demonstrates that the PSO-BP-AdaBoost algorithm can be effectively applied to acoustic seabed classification and identification and achieves high precision.
The airborne light detection and ranging (LiDAR) bathymetry (ALB) system is an extension of the ubiquitous topographic LiDAR mapping system and has been most simply characterized as adding a green ...laser to the infrared laser of topo systems. Due to the low point cloud density and monotonous objects in the scene, it is difficult to mosaicing the ALB strips. Therefore, the existing airborne laser scanning strip stitching algorithm has poor performance for ALB strips. In this article, a coarse-to-fine strip mosaicing model for ALB is proposed. The framework is fast and efficient and can handle large ALB data. An improved alpha shapes algorithm can fast and accurately determine the overlap region of strip is applied. Due to different data accuracy and spatial characteristics, the water area and land area are processed separately. A weight distribution-based coarse-to-fine registration model is designed for underwater areas. The topological constraint term is added to the nonrigid iterative closest point (ICP) cost function to prevent excessive deformation caused by outliers. The implicit B-spline surface fitting algorithm using the 3L algorithm and the least-squares trend surface fitting algorithm are applied separately to assign weights for overlapping strips to solve the limitation of no control or less control. Moreover, a random sample consensus (RANSAC)-ICP registration model characterized by the normal vector and curvature is constructed for land area. Finally, the comparisons with ICP highlight the superiority of the proposed approach in flexibility and accuracy. The root-mean-square error (RMSE) is 0.12 m and the maximum error is 0.36 m.
High electrocatalytic activity with tunable luminescence is crucial for the development of electrochemiluminescence (ECL) luminophores. In this study, a porphyrin‐based heterobimetallic 2D metal ...organic framework (MOF), (ZnTCPP)Co2(MeIm) (1), is successfully self‐assembled from the zinc(II) tetrakis(4‐carboxyphenyl)porphine (ZnTCPP) linker and cobalt(II) ions in the presence of 2‐methylimidazole (MeIm) by a facile one‐pot reaction in methanol at room temperature. On the basis of the experimental results and the theoretical calculations, the MOF 1 contains paddle–wheel Co2(‐CO2)4 secondary building units (SBUs) axially coordinated by a MeIm ligand, which is very beneficial to the electron transfer between the Co(II) ions and oxygen. Combining the photosensitizers ZnTCPP and the electroactive Co2(‐CO2)4 SBUs, the 2D MOF 1 possesses an excellent ECL performance, and can be used as a novel ECL probe for rapid nonamplified detection of the RdRp gene of SARS‐CoV‐2 with an extremely low limit of detection (≈30 aM).
A novel porphyrin‐based heterobimetallic 2D MOF, (ZnTCPP)Co2(MeIm) (1) is constructed to act as an excellent electrochemiluminescence probe for rapid nonamplified detection of SARS‐CoV‐2.
A simple and rapid photoelectrochemical (PEC) sensor was developed for the label-free detection of a phosphoprotein (α-casein) based on a zirconium based porphyrinic metal–organic framework (MOF), ...PCN-222, which exhibited an enhanced photocurrent response toward dopamine under the O2-saturated aqueous media. In this work, in terms of PEC measurements and cyclic voltammetry, the PEC behaviors of PCN-222 in aqueous media were thoroughly investigated for the first time. Additionally, in the virtue of the steric hindrance effect from the coordination of the phosphate groups and inorganic Zr–O clusters as binding sites in PCN-222, this biosensor showed high sensitivity for detecting α-casein and the limit of detection (LOD) was estimated to be 0.13 μg mL–1. Moreover, the proposed method provides a promising platform for clinic diagnostic and therapeutics.
•The changes in maize growth period and soil water content with planting date adjustment.•The suitably delayed planting time can avoid seasonal drought in spring on maize.•A suitable planting date ...have be determined to increase the maize yield and water-use efficiency in rainfed farming systems in arid and semi-arid areas.
Given the frequent drought pressure caused by the unpredictable and limited precipitation concurrent with global climate change, highly efficient cultivation technologies have been increasingly recognized by various levels of scientific communities. Understanding plant–environment relationships in rainfed dry land may help maximize crop productivity while improving water utilization of farmland. Field experiments were conducted in 2012–2014 at the Dryland Maize Experimental Station of the Northwest A&F University, China to determine the effects of possible drought stress and the environmental factors involved during sowing at different sowing dates on maize vegetative growth and grain yield (Zea mays L.), as well as water-use efficiency (WUE=grain yield per unit of seasonal evapotranspiration). Six planting date (PD) treatments with sowing performed for 6 days from April 10 to May 10 were designed. Results showed that the maize growth period was shortened with the postponement of planting time. The vegetative growth stage and the overlapping stages of vegetative and reproductive growth varied by 4–19 days among various PD practices. However, the reproductive growth stage duration was relatively stable and varied by 3–5 days only among the different PD practices. Within a certain time range, dry matter production per plant did not obviously change across the different PD treatments. However, the dry matter accumulation in the ear after flowering, the yield, and the WUE in the treatments under appropriate PDs (April 16–April 28) were 2.2%–28.8%, 2.3%–24.7%, and 6.6%–15.2% higher, respectively, than those in the early or delayed PDs. These findings resulted from the changes in soil water content with PD adjustment. Yield was highly correlated to the soil moisture content during PD, the rainfall before silking, the effective accumulated temperature after silking, and the sunshine hours after silking. Moreover, the thousand-grain weight was highly correlated with the sunshine hours after silking. In the early PDs, the main factor that affected maize yield was the low content of soil moisture, which generated low effective ear number per unit area and seedling emergence ratio. In the late PDs, the main factors that influenced maize yield were the low effective accumulated temperature and the short sunshine hours during the reproductive growth stage, which produced less dry matter accumulation after silking and lower thousand-grain weight. Under suitable sowing time, the actual harvest ear number per hectare and dry matter accumulation of female ear after silking increased. Similarly, the maize yield and WUE increased. By considering the ecological factors and study results, we recommend that the most suitable sowing time for maize should be determined on the basis of the soil moisture content before April 28. As such, we can effectively achieve high yield and avoid drought in the study region. Overall, the results can provide effective cultivation techniques to prevent drought stress in spring maize in the present agro-ecosystem of northern China and other similar areas.
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