公民网络参与的文献综述——基于CiteSpace的图谱量化分析

本研究以中国知网数据库1997-2016年的482篇公民网络参与文献为样本,借助信息可视化软件CiteSpace进行分析.本文通过发文量时间、高被引文献、关键词共现网络节点、时间变化及聚类分析等形式发掘公民网络参与研究的热点及变化趋势.接着,本研究借助聚类分析的结果,按比例从482篇文献中选取代表各个聚类的52篇文献进行分析,从而进一步了解我国公民网络参与的主题、内容以及研究方法.

近十年国内教育数据挖掘领域的应用技术分析

教育数据挖掘是一个跨学科的研究领域,它综合多门学科的方法和技术应用于教育环境,以解决教育问题。为了研究国内近十年教育数据挖掘领域技术使用情况,文章以“教育数据挖掘”为关键词在CNKI进行检索,筛选了2010—2020年125篇教育数据挖掘领域技术类文献,对其技术的使用以及使用变化进行总结分析。研究结果表明,一些传统的数据挖掘方法日渐式微,技术的使用正向多元化、跨领域的方向发展。

燃料电池汽车能量管理测评研究分析

能量管理对燃料电池汽车的经济性能有着重要的影响。本文从现有燃料电池汽车的驱动模式、控制策略、测试工况以及典型燃料电池汽车的能量流测试4个方面进行了综述分析,提出了燃料电池汽车能量流测试评价的关键指标。

Deep Learning Based User Grouping for FD-MIMO Systems Exploiting Statistical Channel State Information

The joint spatial division and multiplexing(JSDM)is a two-phase precoding scheme for massive multiple-input-multiple-output(MIMO)system under frequency division duplex(FDD)mode to reduce the amount of channel state information(CSI)feedback.To apply this scheme,users need to be partitioned into groups so that users in the same group have similar channel covariance eigenvectors while users in different groups have almost orthogonal eigenvectors.In this paper,taking the clustered user model into account,we consider the user grouping of JSDM for the downlink massive MIMO system with uniform planar antenna array(UPA)at base station(BS).A deep learning based user grouping algorithm is proposed to improve the efficiency of the user grouping process.The proposed grouping algorithm transfers the statistical CSI of all users into a picture,and utilizes the deep learning enabled objective detection model you look only once(YOLO)to divide the users into different groups rapidly.Simulation results show that the proposed user grouping scheme can achieve higher sum rate with less time delay.

Superhydrophobic magnetic Fe_(3)O_(4) polyurethane sponges for oil-water separation and oil-spill recovery

The effective and affordable separation of oil and water,a crucial process in the safe han dling of environmental disasters such as crude oil spills and recovery of valuable resources is a highly sought-after yet challenging task.Herein,superhydrophobic PU sponge was fab ricated for the fast and cost-effective adsorptive separation of oil and different organic sol vents from water.Octadecyltrichlorosilane(OTS)-functionalized Fe_(3)O_(4)@SiO_(2)core-shell mi crospheres were dip-coated on the surface of porous materials via a dip-coating process thereby endowing them with superhydrophobicity.Owing to the hydrophobic interaction between OTS molecules and oil and increased capillary force in the micropores,the result ing superhydrophobic sponge served as a selective oil-sorbent scaffold for absorbing oil from oil-water mixtures,including oil-water suspensions and emulsions.Remarkably,after the recovery of the adsorbed oil via mechanical extrusion,these superhydrophobic materials could be reused multiple times and maintain their oil-water separation efficacy even afte 10 oil-water separation cycles.

Tailoring the multiscale mechanics of tunable decellularized extracellular matrix (dECM) for wound healing through immunomodulation

With the discovery of the pivotal role of macrophages in tissue regeneration through shaping the tissue immune microenvironment, various immunomodulatory strategies have been proposed to modify traditional biomaterials. Decellularized extracellular matrix (dECM) has been extensively used in the clinical treatment of tissue injury due to its favorable biocompatibility and similarity to the native tissue environment. However, most reported decellularization protocols may cause damage to the native structure of dECM, which undermines its inherent advantages and potential clinical applications. Here, we introduce a mechanically tunable dECM prepared by optimizing the freeze-thaw cycles. We demonstrated that the alteration in micromechanical properties of dECM resulting from the cyclic freeze-thaw process contributes to distinct macrophage-mediated host immune responses to the materials, which are recently recognized to play a pivotal role in determining the outcome of tissue regeneration. Our sequencing data further revealed that the immunomodulatory effect of dECM was induced via the mechnotrasduction pathways in macrophages. Next, we tested the dECM in a rat skin injury model and found an enhanced micromechanical property of dECM achieved with three freeze-thaw cycles significantly promoted the M2 polarization of macrophages, leading to superior wound healing. These findings suggest that the immunomodulatory property of dECM can be efficiently manipulated by tailoring its inherent micromechanical properties during the decellularization process. Therefore, our mechanics-immunomodulation-based strategy provides new insights into the development of advanced biomaterials for wound healing.

Microstructure and mechanical properties of C_(x)Hf_(0.25)NbTaW_(0.5) refractory high-entropy alloys at room and high temperatures

The microstructure and mechanical properties of as-cast and isothermally annealed C_(x)Hf_(0.25)NbTaW_(0.5)(x=0,0.05,0.15,0.25)refractory high-entropy alloys(RHEAs)were studied.Both the as-cast and annealed RHEAs consisted of disordered body-centered cubic solid solution phase and metal carbide(MC)phase with a face-centered cubic crystal structure(Fm-3 m space group).The primary carbides were enriched with Hf and C elements and tended to form lamellar eutectic-like microstructure in the interdendrites.The lamellar eutectic-like structure in the interdendrites would be formed from the decomposition of sub-carbide M_(2)C under the influence of Hf element.After isothermal annealing,slatted carbides were precipitated on the matrix,and the distribution became more uniform with high C content.The formation of carbides strongly influenced the mechanical properties both at room and high temperatures.The yield strength values of C_(x)Hf_(0.25)NbTaW_(0.5) RHEA at 1473 and 1673 K were 792 and 749 MPa,respectively.The result had exceeded the high temperature mechanical properties of currently known RHEAs.Moreover,this RHEA exhibited high-temperature performance stability and excellent plasticity,exceeding 30 and 50%at room and elevated temperatures(above 1273 K),respectively.During thermal deformation,carbon-containing RHEAs obtained more severe work hardening than that of ACHO RHEAs,and required greater dynamic recrystallization to achieve the dynamic equilibrium.

The influence of two-dimensional organic adlayer thickness on the ultralow frequency Raman spectra of transition metal dichalcogenide nanosheets

Recently, it has been reported that physisorbed adsorbates can be trapped between the bottom surface of twodimensional(2D) materials and supported substrate to form2 D confined films. However, the influence of such 2D confined adsorbates on the properties of 2D materials is rarely explored. Herein, we combined atomic force microscopy(AFM), Kelvin probe force microscopy(KPFM) and Raman spectroscopy especially the ultralow frequency(ULF) Raman spectroscopy to explore the influence of 2D confined organic adlayer thickness on the ULF breathing modes of few-layer MoS2 and WSe2nanosheets. As the thickness of organic adlayers increased, red shift, coexistence of blue and red shifts as well as blue shift of ULF breathing mode was observed. KPFM measurement confirmed the enhanced n-doping and p-doping behaviors of organic adlayers as their thickness increased,respectively. Our results will provide new insights into the interaction between 2D confined adsorbates and bottom surface of 2D nanosheets, which could be useful for modulating properties of 2D materials.