As an abundant and attractive element, the emergence of new carbon-based materials brings revolutionary development in material science and technology. Carbon-based materials have spawned ...considerable interest for fabricating polymer composites/nanocomposites with greatly improved mechanical, thermal, gas barrier, conductivity, and flame retardant performance. In this review, the importance of carbon-based materials and the necessity of fire resistance for polymeric materials are initially introduced. Then, the fundamental flame retardant mechanisms and experimental analytical techniques are described to understand the relationship between structures and flame retardant properties. The main section is dedicated to the preparation and properties of multifunctional polymer composites/nanocomposites with carbon-based materials, with special emphasis on the flame retardant properties of these materials. A wide variety of carbon-based materials are discussed for use in flame retardant polymer nanocomposite, including graphite, graphene, carbon nanotubes, fullerenes as well as some new emerging carbon forms (carbon nitride, carbon aerogels, etc). Finally, a brief outlook at the developments in carbon-based materials for flame retardant polymeric composites is given by discussing the major progress, opportunities, and challenges.
This paper constructs a gray clustering assessment model, combines the indicators of information technology literacy, technology-supported learning, and information technology teaching ability to ...evaluate the information technology teaching ability of A college teachers, and explores the use of information technology equipment of college teachers. And through the construction and calculation of the whitening weight function to refine the classification of college teachers’ informatization teaching ability, for different categories of teachers’ informatization application presenting different characteristics, using one-way ANOVA and adding the Scheffe (C) test to test the inter-group variability of different categories, in-depth exploration of the influencing factors of teachers’ informatization teaching in different categories. The results show that the overall water mean of teachers’ informatization teaching ability in school A is 3.88±0.59, and the model divides teachers’ informatization teaching level in college A into three categories: 3.8-4.5, 3-3.8, and 1-3, with the proportion of each category being 27.8%, 40.1%, and 32.1%, respectively. This study focuses on analyzing the relevant factors affecting teachers’ informatization teaching ability and puts forward countermeasure suggestions according to local conditions, which is of great significance to deepen the reform of education and teaching.
We herein report an optogenetically activatable CRISPR-Cas9 nanosystem for programmable genome editing in the second near-infrared (NIR-II) optical window. The nanosystem, termed nanoCRISPR, is ...composed of a cationic polymer-coated Au nanorod (APC) and Cas9 plasmid driven by a heat-inducible promoter. The APC not only serves as a carrier for intracellular plasmid delivery but also can harvest external NIR-II photonic energy and convert it into local heat to induce the gene expression of the Cas9 endonuclease. Due to high transfection activity, the APC shows strong ability to induce a significant level of disruption in different genomic loci upon optogenetic activation. Moreover, the precise control of genome-editing activity can be simply programmed by finely tuning exposure time and irradiation time in vitro and in vivo and also enables editing at multiple time points, thus proving the sensitivity and inducibility of such an editing modality. The NIR-II optical feature of nanoCRISPR enables therapeutic genome editing at deep tissue, by which treatment of deep tumor and rescue of fulminant hepatic failure are demonstrated as proof-of-concept therapeutic examples. Importantly, this modality of optogenetic genome editing can significantly minimize the off-target effect of CRISPR-Cas9 in most potential off-target sites. The optogenetically activatable CRISPR-Cas9 nanosystem we have developed offers a useful tool to expand the current applications of CRISPR-Cas9, and also defines a programmable genome-editing strategy toward high precision and spatial specificity.
Recently, realistic image generation using deep neural networks has become a hot topic in machine learning and computer vision. Such an image can be generated at pixel level by learning from a large ...collection of images. Learning to generate colorful cartoon images from black-and-white sketches is not only an interesting research problem, but also a useful application in digital entertainment. In this paper, we investigate the sketch-to-image synthesis problem by using conditional generative adversarial networks (cGAN). We propose a model called auto-painter which can automatically generate compatible colors given a sketch. Wasserstein distance is used in training cGAN to overcome model collapse and enable the model converged much better. The new model is not only capable of painting hand-draw sketch with compatible colors, but also allowing users to indicate preferred colors. Experimental results on different sketch datasets show that the auto-painter performs better than other existing image-to-image methods.
All-inorganic CsPbI
perovskite quantum dots have received substantial research interest for photovoltaic applications because of higher efficiency compared to solar cells using other quantum dots ...materials and the various exciting properties that perovskites have to offer. These quantum dot devices also exhibit good mechanical stability amongst various thin-film photovoltaic technologies. We demonstrate higher mechanical endurance of quantum dot films compared to bulk thin film and highlight the importance of further research on high-performance and flexible optoelectronic devices using nanoscale grains as an advantage. Specifically, we develop a hybrid interfacial architecture consisting of CsPbI
quantum dot/PCBM heterojunction, enabling an energy cascade for efficient charge transfer and mechanical adhesion. The champion CsPbI
quantum dot solar cell has an efficiency of 15.1% (stabilized power output of 14.61%), which is among the highest report to date. Building on this strategy, we further demonstrate a highest efficiency of 12.3% in flexible quantum dot photovoltaics.
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•The poly(aniline-co-pyrrole) random copolymer was successfully synthesized.•A strong interaction between the pyrrole and the aniline units was detected on the PANiPy chain.•A ...self-assembled layered morphology was formed between SWCNT and PANiPy.•A highest power factor of 98.5 μW·m−1·k−2 was achieved in PANiPy/SWCNTs composite.
The electrical conductivity of conducting polymer depends strongly on the alignment of the polymer chains, and a fully aligned polymer backbone strongly enhances the conjugation. Herein, the pyrrole unit was introduced onto the polyaniline backbone to improve the alignment of the polyaniline (PANi) main chain. The nanostructured poly(aniline-co-pyrrole) random copolymer (PANiPy) was successfully synthesized via a sustainable method without mechanical agitation. FTIR, Raman and XPS spectra confirmed the strong interaction between the pyrrole and the aniline units. Single wall carbon nanotubes (SWCNTs) were applied to improve the membrane forming performance of insoluble conjugated polymers and the polymer/SWCNT composites were prepared. The SEM results revealed that the synthesized polymer exhibited a nanostructured morphology. Nanostructured PANiPy was well dispersed in the SWCNT bundles and formed a self-assembled layered morphology. The PANiPy/SWCNT composite film achieved the highest power factor of 98.5 μW·m−1·k−2, which was much higher than that most carbon-based thermoelectric composites. The results demonstrated that introducing the pyrrole units onto the PANi backbone was a good strategy to tune the alignment of PANi chain, and the thermoelectric performance of PANi/SWCNT composite was enhanced. Moreover, the experimental procedure is attractive as a sustainable process for materials preparation in chemical engineering.
One of the biggest challenges in content based image retrieval is to solve the problem of “semantic gaps” between low-level features and high-level semantic concepts. In this paper, we aim to ...investigate various combinations of mid-level features to build an effective image retrieval system based on the bag-of-features (BoF) model. Specifically, we study two ways of integrating the SIFT and LBP descriptors, HOG and LBP descriptors, respectively. Based on the qualitative and quantitative evaluations on two benchmark datasets, we show that the integrations of these features yield complementary and substantial improvement on image retrieval even with noisy background and ambiguous objects. Two integration models are proposed: the patch-based integration and image-based integration. By using a weighted K-means clustering algorithm, the image-based SIFT-LBP integration achieves the best performance on the given benchmark problems comparing to the existing algorithms.
A novel region-based image fusion framework based on multiscale image segmentation and statistical feature extraction is proposed. A dual-tree complex wavelet transform (DT-CWT) and a statistical ...region merging algorithm are used to produce a region map of the source images. The input images are partitioned into meaningful regions containing salient information via symmetric alpha-stable (S alphaS) distributions. The region features are then modeled using bivariate alpha-stable (B alphaS) distributions, and the statistical measure of similarity between corresponding regions of the source images is calculated as the Kullback-Leibler distance (KLD) between the estimated B alphaS models. Finally, a segmentation-driven approach is used to fuse the images, region by region, in the complex wavelet domain. A novel decision method is introduced by considering the local statistical properties within the regions, which significantly improves the reliability of the feature selection and fusion processes. Simulation results demonstrate that the bivariate alpha-stable model outperforms the univariate alpha-stable and generalized Gaussian densities by not only capturing the heavy-tailed behavior of the subband marginal distribution, but also the strong statistical dependencies between wavelet coefficients at different scales. The experiments show that our algorithm achieves better performance in comparison with previously proposed pixel and region-level fusion approaches in both subjective and objective evaluation tests.
AIM To analyze the risk factors for pancreatic fistula after pancreaticoduodenectomy.METHODS We conducted a retrospective analysis of 539 successive cases of pancreaticoduodenectomy performed at our ...hospital from March 2012 to October 2015. Pancreatic fistula was diagnosed in strict accordance with the definition of pancreatic fistula from the International Study Group on Pancreatic Fistula. The risk factors for pancreatic fistula were analyzed by univariate analysis and multivariate logistic regression analysis.RESULTS A total of 269(49.9%) cases of pancreatic fistula occurred after pancreaticoduodenectomy,including 71(13.17%) cases of grade A pancreatic fistula,178(33.02%) cases of grade B,and 20(3.71%) cases of grade C. Univariate analysis showed no significant correlation between postoperative pancreatic fistula(POPF) and the following factors: age,hypertension,alcohol consumption,smoking,history of upper abdominal surgery,preoperative jaundice management,preoperative bilirubin,preoperative albumin,pancreatic duct drainage,intraoperative blood loss,operative time,intraoperative blood transfusion,Braun anastomosis,and pancreaticoduodenectomy(with or without pylorus preservation). Conversely,a significant correlation was observed between POPF and the following factors: gender(male vs female: 54.23% vs 42.35%,P = 0.008),diabetes(non-diabetic vs diabetic: 51.61% vs 39.19%,P = 0.047),body mass index(BMI)(≤ 25 vs > 25: 46.94% vs 57.82%,P = 0.024),blood glucose level(≤ 6.0 mmol/L vs > 6.0 mmol/L: 54.75% vs 41.14%,P = 0.002),pancreaticojejunal anastomosis technique(pancreatic duct-jejunum double-layer mucosa-to-mucosa pancreaticojejunal anastomosis vs pancreatic-jejunum single-layer mucosa-tomucosa anastomosis: 57.54% vs 35.46%,P = 0.000),diameter of the pancreatic duct(≤ 3 mm vs > 3 mm: 57.81% vs 38.36%,P = 0.000),and pancreatic texture(soft vs hard: 56.72% vs 29.93%,P = 0.000). Multivariate logistic regression analysis showed that gender(male),BMI > 25,pancreatic duct-jejunum double-layer mucosa-to-mucosa pancreaticojejunal anastomosis,pancreatic duct diameter ≤ 3 mm,and soft pancreas were risk factors for pancreatic fistula after pancreaticoduodenectomy.CONCLUSION Gender(male),BMI > 25,pancreatic duct-jejunum double-layer mucosa-to-mucosa pancreaticojejunal anastomosis,pancreatic duct diameter ≤ 3 mm,and soft pancreas were risk factors for pancreatic fistula after pancreaticoduodenectomy.
Virtual synchronous generator technology can effectively improve the anti‐interference characteristics of the system frequency and bus voltage in the microgrid, and solve the problems of insufficient ...damping and low inertia of the system. However, in an islanded microgrid with multiple distributed generation, the difference in line impedance will cause local voltage deviations, which in turn leads to a series of problems, such as reducing power distribution accuracy and increasing bus voltage drop. Therefore, for the island‐type microgrid multi‐inverter distributed power generation parallel system, in order to solve the problem of low power distribution accuracy and large frequency oscillation caused by system parameters in virtual synchronous generator control, an improved virtual synchronous generator control algorithm based on adaptive droop coefficient is proposed in this paper, which not only eliminates the resistance component of the line impedance, makes the system impedance characteristic present a purely inductive nature, but also realises real‐time adjustment of active and reactive power. While maintaining the stability of the bus voltage and system frequency, it maintains high power distribution accuracy and improves the dynamic performance and operational stability of the power grid system.
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