离心叶轮流场对背压脉动的响应特性研究

本文首先采用数值模拟方法开展高速离心压缩机叶轮出口下游背压脉动的流场响应特性研究,分析指出高转速离心叶轮的气动性能波动随着背压脉动频率的增加而增大,但不同背压脉动频率下各时刻的流场分布具有相似结构。然后采用动态模态分解(DMD)方法对背压脉动下非定常流动的模态场进行分析,不同脉动频率下的非定常流场均包含叶轮转频的各阶谐波模态,流场响应的零阶模态为反映平均流场的基本模态,各阶谐波模态均为极限环模态,其它均为近似极限环振荡或衰减模态,流场响应的非定常成分主要由一阶谐波模态贡献。DMD分析结果表明:DMD方法能够对叶轮非定常流场变化特性进行降阶解构及准确预测。

3D printing of architectured graphene-based aerogels by cross-linking GO inks with adjustable viscoelasticity for energy storage devices

Three-dimensional(3D)functional graphenebased architecture with superior electrical conductivity and good mechanical strength has promising applications in energy storage and electrics.Viscoelasticity-adjustable inks make it possible to achieve desired 3D architectures with interconnected and continuous interior networks by microextrusion printing.In this work,ultra-low-concentration graphene oxide(GO)inks of~15 mg·ml-1 have been obtained and demonstrated in direct 3D printing with a facile cross-linking(direct ink writing).The rheological behavior of the GO strategy by cations,which is the lowest concentration to achieve direct ink writing inks,could be adjusted from 1×10^(4) to 1×10^(5) Pa·s^(-1) with different concentrations of cations due to strong cross-linking networks between GO sheets and cations.Meanwhile,the specific strength and electrical conductivity of 3D-printed graphene architecture are notably enhanced,reaching up to 51.7×10^(3) N·m·kg^(-1)and 119 S·m^(-1),which are superior to conventional graphene aerogels.Furthermore,3D printing graphene-based architecture assembled in micro-superc apacitor exhibits excellent electrochemical performance,which can be ascribed to the effective ion transportation through the interconnected networks.The strategy demonstrated is useful in the design of complex-shaped,graphene-based architectures for scalable manufacturing of practical energy storage applications.

Underwater Superoleophobic-Oleophilic Chips for Femtomolar Aflatoxins Identification

Underwater superoleophobic-oleophilic chips were developed to achieve oil extracting from aqueous solution and oil-droplet con-densing to preset microwell.The double-hierarchical(extracting-condensing)enrichment strategy drastically improves the sensitivi-ty for organic contaminants or components,whose signal amplification approaches 459.7 times that of primary solution and 25.9 times that of single condensing enrichment strategy.Low to femtomolar limit of detection(2.6×10^(-15)mol/L)sensitivity and 6 vari-ous aflatoxins or mildewed foods identification demonstrate the significance and promotion for environment monitoring,water pu-rification,and so on.

Augmented Flow Simulation Based on Tight Coupling Between Video Reconstruction and Eulerian Models

Hybrid approaches such as combining video data with pure physics-based simulation have been popular in the recent decade for computer graphics. The key motivation is to clearly retain salient advantages from both data-driven method and model-centric numerical simulation, while overcoming certain difficulties of both. The Eulerian method, which has been widely employed in flow simulation, stores variables such as velocity and density on regular Cartesian grids, thereby it could be associated with （volumetric） video data on the same domain. This paper proposes a novel method for flow simulation, which is tightly coupling video-based reconstruction with physically-based simulation and making use of meaningful physical attributes during re-simulation. First, we reconstruct the density field from a single-view video. Second, we estimate the velocity field using the reconstructed density field as prior. In the iterative process, the pressure projection can be treated as a physical constraint and the results of each step are corrected by obtained velocity field in the Eulerian framework. Third, we use the reconstructed density field and velocity field to guide the Eulerian simulation with anticipated new results. Through the guidance of video data, we can produce new flows that closely match with the real scene exhibited in data acquisition. Moreover, in the multigrid Eulerian simulation, we can generate new visual effects which cannot be created from raw video acquisition, with a goal of easily producing many more visually interesting results and respecting true physical attributes at the same time. We demonstrate salient advantages of our hybrid method with a variety of animation examples.

Multicenter evaluation of a simple and sensitive nucleic acid self-testing for SARS-CoV-2

A rapid and accurate COVID-19 diagnosis is a prerequisite for blocking the source of infection as soon as possible and taking the appropriate medical action.Herein,we developed GeneClick,a device for nucleic acid self-testing of SARS-CoV-2,consisting of three modules:a sampling kit,a microfluidic chip-based disposable cartridge,and an amplification reader.In addition,we evaluated the clinical performance of GeneClick using 2162 nasal swabs collected at three medical institutions,using three commercial RT-qPCR kits and an antigen self-test as references.Compared to RT-qPCR,the sensitivity and specificity of the GeneClick assay were 97.93%and 99.72%,respectively,with a kappa value of 0.979(P<0.01).Of the 2162 samples,2076 were also tested for SARS-CoV-2 antigens.Among the 314 positive samples identified by GeneClick assay,63 samples were undetected by antigen tests.Overall,the GeneClick nucleic acid self-test demonstrated higher accuracy than the antigen-based detection.Based on the additional features,including simple operation,affordable price,portable device,and reliability of smartphone APP-driven sampling and result reporting,GeneClick offers a powerful tool for field-based SARS-CoV-2 detection in primary healthcare institutions or at-home use.