多孔氮掺杂FeP/C纳米纤维作为钾离子电池负极

由于自然界中钾储量巨大且K+/K电位低,钾离子电池(PIBs)被认为是锂离子电池的替代品之一。因此,在这项工作中,我们合成了多孔氮掺杂FeP/C纳米纤维(P-FeP/C-N NFs),一种用于PIB的新型电极材料。通过简单的静电纺丝和随后的煅烧处理,将聚丙烯腈(PAN)和聚甲基丙烯酸甲酯(PMMA)分别用作氮源和造孔剂,引入氮提高了材料的导电性,多孔结构的形成增加了比表面积。将P-FeP/CN NFs用作钾离子电池的电极,表现出优异的电化学性能。P-FeP/C-N NFs电极在100 mA/g循环250次后放电容量为274.2 mA·h/g,在1000 mA/g循环300次后放电容量为171.3 mA·h/g。即使在5000 mA/g下,也显示出150.1 mA·h/g的高放电容量。结果表明P-FeP/C-N NFs有望成为钾离子电池负极材料的候选材料。

Restraining migration and dissolution of transition-metal-ions via functionalized separator for Li-rich Mn-based cathode with high-energy-density

Lithium-rich manganese-based materials(LRMs) are promising cathode for high-energy-density lithiumion batteries due to their high capacity,low toxicity,and low cost.However,LRMs suffer from serious voltage decay and capacity fade due to continual migration and dissolution of transition metal ions(TMs) during cycling process.Herein,a novel strategy is proposed to inhibit the TMs migration of LRMs through a modified separator by means of functionalized carbon coating layer,which depends on the chemical constraint of the abundant functional groups in the modified super P.In addition,it has been found that the dissolution of TMs can be restrained based on the Le Chatelier's principle.Moreover,the modified separator owns good wettability toward the electrolyte.As a result,the LRMs cathode with the modified separator delivers a high discharge capacity of 329.93 mA h g-1 at 0.1 C,and achieves good cyclic performance,the enhanced reaction kinetics and low voltage decay.Therefore,this work provides a new idea to promote the comprehensive electrochemical performances of Li-ion batteries with LRMs cathode through a strategy of separator modification.

Study on Evaluation Method of Failure Pressure for Pipeline with Axially Adjacent Defects

The interaction between axially adjacent defects is more significant than that between circumferentially aligned defects.However,the existing failure pressure assessment methods cannot accurately predict the failure pressure of axial adjacent defects.In the paper,the finite element model is adopted to analyze the influence of defect size,distribution mode and spacing between adjacent defects on failure pressure.A new failure pressure evaluation method is proposed by establishing the effective depth calculation model of corrosion colony with different distribution model.The burst test of X52 pipeline is carried out to verify the applicability of the method.It shows that the results of new method are consistent with the test results of pipeline with various defects and steel grades.

Mapping theme trends and knowledge structures for human neural stem cells:a quantitative and co-word biclustering analysis for the 2013-2018 period

Neural stem cells,which are capable of multi-potential differentiation and self-renewal,have recently been shown to have clinical potential for repairing central nervous system tissue damage.However,the theme trends and knowledge structures for human neural stem cells have not yet been studied bibliometrically.In this study,we retrieved 2742 articles from the PubMed database from 2013 to 2018 using "Neural Stem Cells" as the retrieval word.Co-word analysis was conducted to statistically quantify the characteristics and popular themes of human neural stem cell-related studies.Bibliographic data matrices were generated with the Bibliographic Item Co-Occurrence Matrix Builder.We identified 78 high-frequency Medical Subject Heading(MeSH)terms.A visual matrix was built with the repeated bisection method in gCLUTO software.A social network analysis network was generated with Ucinet 6.0 software and GraphPad Prism 5 software.The analyses demonstrated that in the 6-year period,hot topics were clustered into five categories.As suggested by the constructed strategic diagram,studies related to cytology and physiology were well-developed,whereas those related to neural stem cell applications,tissue engineering,metabolism and cell signaling,and neural stem cell pathology and virology remained immature.Neural stem cell therapy for stroke and Parkinson’s disease,the genetics of microRNAs and brain neoplasms,as well as neuroprotective agents,Zika virus,Notch receptor,neural crest and embryonic stem cells were identified as emerging hot spots.These undeveloped themes and popular topics are potential points of focus for new studies on human neural stem cells.

Neuroregeneration and functional recovery after stroke: advancing neural stem cell therapy toward clinical application

Stroke is a main cause of death and disability worldwide.The ability of the brain to selfrepair in the acute and chronic phases after stroke is minimal;however,promising stem cell-based interventions are emerging that may give substantial and possibly complete recovery of brain function after stroke.Many animal models and clinical trials have demonstrated that neural stem cells(NSCs)in the central nervous system can orchestrate neurological repair through nerve regeneration,neuron polarization,axon pruning,neurite outgrowth,repair of myelin,and remodeling of the microenvironment and brain networks.Compared with other types of stem cells,NSCs have unique advantages in cell replacement,paracrine action,inflammatory regulation and neuroprotection.Our review summarizes NSC origins,characteristics,therapeutic mechanisms and repair processes,then highlights current research findings and clinical evidence for NSC therapy.These results may be helpful to inform the direction of future stroke research and to guide clinical decision-making.

Progress in clinical trials of stem cell therapy for cerebral palsy

Cerebral palsy is the most common disease in children associated with lifelong disability in many countries.Clinical research has demonstrated that traditional physiotherapy and rehabilitation therapies cannot alone cure cerebral palsy.Stem cell transplantation is an emerging therapy that has been applied in clinical trials for a variety of neurological diseases because of the regenerative and unlimited proliferative capacity of stem cells.In this review, we summarize the design schemes and results of these clinical trials.Our findings reveal great differences in population characteristics, stem cell types and doses, administration methods, and evaluation methods among the included clinical trials.Furthermore, we also assess the safety and efficacy of these clinical trials.We anticipate that our findings will advance the rational development of clinical trials of stem cell therapy for cerebral palsy and contribute to the clinical application of stem cells.

Caveolin-1 downregulation promotes the dopaminergic neuron-like differentiation of human adipose-derived mesenchymal stem cells

Previous studies have shown that caveolin-1 is involved in regulating the differentiation of mesenchymal stem cells.However,its role in the differentiation of human adipose mesenchymal stem cells into dopaminergic neurons remains unclear.The aim of this study was to investigate whether caveolin-1 regulates the differentiation of human adipose mesenchymal stem cells into dopaminergic-like neurons.We also examined whether the expression of caveolin-1 could be modulated by RNA interference technology to promote the differentiation of human adipose mesenchymal stem cells into dopaminergic-like neurons.The differentiation of human adipose mesenchymal stem cells into dopaminergic neurons was evaluated morphologically and by examining expression of the markers tyrosine hydroxylase,Lmx1a and Nurr1.The analyses revealed that during the differentiation of human adipose mesenchymal stem cells into dopaminergic neurons,the expression of caveolin-1 is decreased.Notably,the downregulation of caveolin-1 promoted the differentiation of human adipose mesenchymal stem cells into dopaminergic-like neurons,and it increased the expression of tyrosine hydroxylase,Lmx1a and Nurr1.Together,our findings suggest that caveolin-1 plays a negative regulatory role in the differentiation of dopaminergic-like neurons from stem cells,and it may therefore be a potential molecular target for strategies for regulating the differentiation of these cells.This study was approved by the Medical Ethics Committee of the First Affiliated Hospital of Dalian Medical University of China(approval No.PJ-KS-KY-2020-54)on March 7,2017.

Human umbilical cord-derived mesenchymal stem cells promote repair of neonatal brain injury caused by hypoxia/ischemia in rats

Administration of human umbilical cord-derived mesenchymal stem cells(hUC-MSCs)is believed to be an effective method for treating neurodevelopmental disorde rs.In this study,we investigated the possibility of hUC-MSCs treatment of neonatal hypoxic/ischemic brain injury associated with maternal immune activation and the underlying mechanism.We established neonatal rat models of hypoxic/ischemic brain injury by exposing pregnant rats to lipopolysaccharide on day 16 or 17 of pregnancy.Rat offspring were intranasally administe red hUC-MSCs on postnatal day 14.We found that polypyrimidine tract-binding protein-1(PTBP-1)participated in the regulation of lipopolysaccharide-induced maternal immune activation,which led to neonatal hypoxic/ischemic brain injury.Intranasal delive ry of hUC-MSCs inhibited PTBP-1 expression,alleviated neonatal brain injury-related inflammation,and regulated the number and function of glial fibrillary acidic protein-positive astrocytes,there by promoting plastic regeneration of neurons and im p roving brain function.These findings suggest that hUC-MSCs can effectively promote the repair of neonatal hypoxic/ischemic brain injury related to maternal immune activation through inhibition of PTBP-1 expression and astrocyte activation.

Template-Free Synthesis of Sb_2S_3 Hollow Microspheres as Anode Materials for Lithium-Ion and Sodium-Ion Batteries

Hierarchical Sb_2S_3 hollow microspheres assembled by nanowires have been successfully synthesized by a simple and practical hydrothermal reaction. The possible formation process of this architecture was investigated by X-ray diffraction, focused-ion beam-scanning electron microscopy dual-beam system, and transmission electron microscopy. When used as the anode material for lithium-ion batteries, Sb_2S_3 hollow microspheres manifest excellent rate property and enhanced lithium-storage capability and can deliver a discharge capacity of 674 m Ah g^(-1) at a current density of 200 m A g^(-1) after 50 cycles. Even at a high currentdensity of 5000 m A g^(-1), a discharge capacity of541 m Ah g^(-1) is achieved. Sb_2S_3 hollow microspheres also display a prominent sodium-storage capacity and maintain a reversible discharge capacity of 384 m Ah g^(-1) at a current density of 200 m A g^(-1) after 50 cycles. The remarkable lithium/sodium-storage property may be attributed to the synergetic effect of its nanometer size and three-dimensional hierarchical architecture, and the outstanding stability property is attributed to the sufficient interior void space,which can buffer the volume expansion.

Acoustic pressure simulation and experiment design in seafloor mining environment

针对海底采矿环境下,悬浮泥沙对换能器声场分布影响严重的问题,基于KZK(Khokhlov–Zabolotkaya–Kuznetsov)方程,提出了混浊水域中声场分析方法。首先,对清洁水域声吸收和悬浮泥沙引起的粘滞声吸收进行分析,并由此建立采矿环境下声衰减系数随频率变化的规律曲线。然后,利用MATLAB,通过KZK方程的频域求解方法,对清洁水域和混浊水域中换能器轴向声场进行数值计算。仿真结果表明,悬浮泥沙对近场距离内轴向声压的影响不大,而随着距离的增大,换能器轴向声压幅值很快衰减,悬浮泥沙使远场区声压幅值严重降低。模拟采矿实验测量频率为200 kHz,波束角为7.5°换能器的轴向声压分布,结果表明,仿真结果与实验结果的一致性较好,KZK方程可以有效描述混浊水域中的声场分布。

Influence of multi-stage heat treatment on the microstructure and mechanical properties of TC21 titanium alloy

Duplex-structured TC21 alloy samples were first solution-treated at a higher temperature in theα+βregion(940°C)with furnace cooling(FC),air cooling(AC),and water cooling(WC),followed by a second-stage solution treatment at a lower temperature in theα+βregion(900°C),and then finally aged at 590°C.The effects of the morphology and quantity ofαphases on the structure and properties of the TC21 alloy after the different heat treatments were analyzed.The in-situ tensile deformation process and crack propagation behavior were observed using scanning electron microscopy(SEM).The quantity of equiaxedαphases as well as the thickness of lamellarαphases reduced,the tensile strength increased firstly and then decreased,the elongation decreased with the increasing cooling rate after the first-stage solution treatment.The amount and size of lamellarαphases increased after the second-stage solution treatment because of sufficient diffusion of the alloying elements,thereby leading to increased tensile strength.The amount of dispersedαphases increased after the third-stage aging treatment owing to the increase in the nucleation rate,resulting in a noteworthy strengthening effect.After the third-stage aging treatment,the first-stage FC sample exhibited better mechanical properties because it contained more equiaxedαandβtrans phases than the first-stage AC and WC samples.

钠离子电池正极复合材料Na0.44MnO2/石墨烯的合成与性能（英文）

本文通过水热法合成了Na0.44MnO2纳米棒,并系统地研究和优化了合成该材料的实验参数。实验结果表明,在200℃下,水热反应16 h获得的Na0.44MnO2纳米棒展现了最好的电化学性能。在2.0~4.0 V的电压窗口,50mA/g电流密度下,该材料具有110.7mA·h/g的初始放电比容量,循环100周后的容量保持率为74.7%。为了进一步提高该材料的电化学性能,将石墨烯与其混合球磨,得到了Na0.44MnO2/石墨烯复合材料。在50mA/g电流密度下,该复合材料首次放电比容量为106.9mA·h/g,100周循环后,放电比容量仍保持为91.8mA·h/g,容量保持率为85.9%。此外,当电流密度提高到500和1000 mA/g时,该复合材料分别具有89和78mA·h/g的放电比容量。与石墨烯复合,Na0.44MnO2材料的循环性能与倍率性能得到了显著提高。

简单固相法合成锂离子电池用Na2FePO4F/C复合材料（英文）

选用二水合磷酸铁为铁源,经乙醇辅助球磨和固相反应制备了氟磷酸亚铁钠/碳复合材料。X-射线衍射证实产品有高的结晶度和相纯度。扫描电镜和透射电镜照片显示,球形氟磷酸亚铁钠粒子的粒径分布在50~300 nm之间;从高分辨透射电镜图可以看出,在氟磷酸亚铁钠/碳复合材料的表面包覆了一层厚度为3.6 nm的碳层。碳层的包覆能有效地遏制氟磷酸亚铁钠粒子的长大及粒子的团聚。以锂片作为负极组装半电池,在0.5C,1C,2C倍率下,复合材料的放电比容量分别为102.8,96.4,90.3 mA·h/g。0.5C循环100次后电池的放电比容量为98.9 mA·h/g,容量保持率为96.2%。从循环伏安曲线计算得到氟磷酸亚铁钠/碳复合材料的锂离子扩散系数为1.71×10^–9cm^2/s。显然,固相法是制备锂离子电池正极材料用氟磷酸亚铁钠/C复合材料的有效方法。

Intelligent Segmentation and Measurement Model for Asphalt Road Cracks Based on Modified Mask R-CNN Algorithm

Nowadays, asphalt road has dominated highways around the world. Among various defects of asphalt road, crackshave been paid more attention, since cracks often cause major engineering and personnel safety incidents. Currentmanual crack inspection methods are time-consuming and labor-intensive, and most segmentation methods cannot detect cracks at the pixel level. This paper proposes an intelligent segmentation and measurement model basedon the modified Mask R-CNN algorithm to automatically and accurately detect asphalt road cracks. The modelproposed in this paper mainly includes a convolutional neural network (CNN), an optimized region proposalnetwork (RPN), a region of interest (RoI) Align layer, a candidate area classification network and a Mask branch offully convolutional network (FCN). The ratio and size of anchors in the RPN are adjusted to improve the accuracyand efficiency of segmentation. Soft non-maximum suppression (Soft-NMS) algorithm is developed to improvethe segmentation accuracy. A dataset including 8,689 images (512× 512 pixels) of asphalt cracks is established andthe road crack is manually marked. Transfer learning is used to initialize the model parameters in the trainingprocess. To optimize the model training parameters, multiple comparison experiments are performed, and the testresults show that the mean average precision (mAP) value and F1-score of the optimal trained model are 0.952 and0.949. Subsequently, the robustness verification test and comparative test of the trained model are conducted andthe topological features of the crack are extracted. Then, the damage area, length and average width of the crackare measured automatically and accurately at pixel level. More importantly, this paper develops an automatic crackdetection platform for asphalt roads to automatically extract the number, area, length and average width of cracks,which can significantly improve the crack detection efficiency for the road maintenance industry.

Dielectric Characterization and Microwave Roasting of Molybdenite Concentrates at 915 MHz Frequency

The magnetic hysteresis loop was measured to know the magnetic property of molybdenite concentrate.In order to evaluate its microwave absorption capacity, the dielectric properties of molybdenite concentrate was investigated using cavity perturbation method at 915 MHz dependent on densities and temperatures.The parameter data were fitted using regression fit and a model related to the same density and temperature ranges was developed.A nonlinear surface fitting was used to present visually the effect of dielectric parameters on the microwave penetrate depth of molybdnite concentrate.The crystal products of MoO 3 obtained from microwave roasting at different temperatures were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD).The results show both the dielectric constants and loss factors increase in the increase of apparent densities and temperatures with different growth rates in the experimental range.Due to the distinguished trend of dielectric performance dependent on temperatures, two parts in the heating scenario for the molybdenite concentrate samples were divided.The microwave penetration depth is inversely proportional to both apparent densities and temperatures.The nonlinear fitting surfaces indicate the increase of dielectric loss provides an enough decrease in microwave penetration depth.In contrast, the dielectric constant has a positive effect for it.Pure MoO 3 was produced at 800 ℃ by using microwave energy.This work can be helpful to design and simulate microwave system for efficient beneficiation of molybdenite concentrate and to prepare molybdenum products from this concentrate.

Free-standing ternary metallic sulphides/Ni/C-nanofiber anodes for high-performance lithium-ion capacitors

As a promising energy-storage device,the hybrid lithium-ion capacitor coupling with both a large energy density battery-type anode and a high power density capacitor-type cathode is attracting great attention.For the sake of improving the energy density of hybrid lithium-ion capacitor,the free-standing anodes with good electrochemical performance are essential.Herein,we design an effective electrospinning strategy to prepare free-standing MnS/Co4S3/Ni3S2/Ni/C-nanofibers(TMSs/Ni/C-NFs)film and firstly use it as a binder-free anode for hybrid lithium-ion capacitor.We find that the carbon nanofibers can availably prevent MnS/Co4S3/Ni3S2/Ni nanoparticles from aggregation as well as significantly improve the electrochemical performance.Therefore,the binder-free TMSs/Ni/C-NFs membrane displays an ultrahigh reversible capacity of 1246.9 m Ah g-1at 100 m A g-1,excellent rate capability(398 mAh g-1 at2000 mA g-1),and long-term cyclic endurance.Besides,we further assemble the hybrid lithium-ion capacitor,which exhibits a high energy density of 182.0 Wh kg-1at 121.1 W kg-1(19.0 Wh kg-1 at 3512.5 W kg-1)and remarkable cycle life.

Stability Analysis of Cross-Channel Excavation for Existing Anchor Removal Project in Subway Construction

The cutter head will be stuck when the shield machine pass through the area existing anchor left by foundation construction of surrounding high-rise building.Subsurface excavation method is an efficient way to remove the existed anchor.In this paper,a three-dimensional finite element model is developed to study stability of cross-channel excavation.The time-spatial effects of arch crown settlement,intrados uplift and side wall horizontal convergence are analyzed according to different excavation size,lining thickness and lining order.The results show that the excavation size is the main factor to control the deformation of the surrounding soil,especially in arch crown settlement;The influence of lining thickness on the spatial effect of surrounding soil deformation is obvious when the excavation size is large,but little on the time effect;The influence of the lining order on the deformation of the surrounding soil is obvious,in particular,the larger the excavation size,the more obvious advantages of the lining order.Finally,based on the time-spatial effects comparison of nine excavation schemes of the cross-channel,an optimum excavation scheme is adopted in the actual project.

Dielectric Properties and Microwave Heating of Molybdenite Concentrate at 2.45 GHz Frequency

Dielectric properties were measured using cavity perturbation method. The temperature rising behaviors of molybdenite concentrate were investigated in the field of microwave. This process was conducted to show the microwave absorption properties of molybdenite concentrate and the feasibility of microwave roasting molybdenite concentrate to prepare high purity M_OO_3. The dielectric constant,dielectric loss,and loss tangent increase from 3. 51 to 5. 04,0. 22 to 0. 51 and 0. 065 to 0. 102 respectively. They are proportional to the apparent density of molybdenite concentrate in the range of 0. 9-1. 4 g/cm3. The results show that the molybdenite concentrate has good microwave absorption capacity in the conventional density range. The temperature rising curves show that the apparent heating rate of the molybdenite concentrate increases with the increase in microwave power and decreases with the increase in the sample mass and thickness. The temperature of concentrate sample of 100 g reaches approximately 800 ℃ after 5 min of microwave treatment at 0. 5 kW of power. Our findings show that it is feasible to prepare high-purity M_OO_3 from molybdenite concentrate by microwave roasting.

Nitrogen-Doped TiO_2–C Composite Nanofibers with High-Capacity and Long-Cycle Life as Anode Materials for Sodium-Ion Batteries

Nitrogen-doped TiO_2–C composite nanofibers(TiO_2/N–C NFs) were manufactured by a convenient and green electrospinning technique in which urea acted as both the nitrogen source and a pore-forming agent. The TiO_2/N–C NFs exhibit a large specific surface area(213.04 m^2 g^(-1)) and a suitable nitrogen content(5.37 wt%). The large specific surface area can increase the contribution of the extrinsic pseudocapacitance, which greatly enhances the rate capability. Further, the diffusion coefficient of sodium ions(DNa_+) could be greatly improved by the incorporation of nitrogen atoms. Thus, the TiO_2/N–C NFs display excellent electrochemical properties in Na-ion batteries. A TiO_2/N–C NF anode delivers a high reversible discharge capacity of 265.8 mAh g^(-1) at 0.05 A g^(-1) and an outstanding long cycling performance even at a high current density(118.1 m Ah g^(-1)) with almost no capacity decay at 5 A g^(-1) over 2000 cycles. Therefore, this work sheds light on the application of TiO_2-based materials in sodium-ion batteries.

Wire-in-Wire TiO_(2)/C Nanofibers Free-Standing Anodes for Li-Ion and K-Ion Batteries with Long Cycling Stability and High Capacity

Wearable and portable mobile phones play a critical role in the market, and one of the key technologies is the flexible electrode with high specific capacity and excellent mechanical flexibility. Herein, a wire-in-wire TiO_(2)/C nanofibers (TiO_(2) ww/CN) film is synthesized via electrospinning with selenium as a structural inducer. The interconnected carbon network and unique wire- in-wire nanostructure cannot only improve electronic conductivity and induce effective charge transports, but also bring a superior mechanic flexibility. Ulti-mately, TiO_(2) ww/CN film shows outstanding electrochemical performance as free-standing electrodes in Li/K ion batteries. It shows a discharge capacity as high as 303 mAh g^(−1) at 5 A g^(−1) after 6000 cycles in Li half-cells, and the unique structure is well-reserved after long-term cycling. Moreover, even TiO_(2) has a large diffusion barrier of K^(+), TiO_(2) ww/CN film demonstrates excellent perfor-mance (259 mAh g^(−1) at 0.05 A g^(−1) after 1000 cycles) in K half-cells owing to extraordinary pseudocapacitive contribution. The Li/K full cells consisted of TiO_(2) ww/CN film anode and LiFePO_(4)/Perylene-3,4,9,10-tetracarboxylic dianhydride cathode possess outstanding cycling stability and demonstrate practical application from lighting at least 19 LEDs. It is, therefore, expected that this material will find broad applications in portable and wearable Li/K-ion batteries.