朔黄铁路重载列车电控空气制动试验研究

重载列车的制动技术是重载运输发展的关键。针对国内朔黄铁路,对重载列车电控空气制动系统进行试验研究,比较分析有无电控空气制动系统作用下列车制动系统的性能指标。实验结果显示:电控空气制动系统性能指标达到设计要求,在缓解车钩作用力、同步列车管及制动缸压力和缩短制动距离等方面具有明显的优势,该电控空气制动系统能够保证重载长、大列车运行的安全性。

VMD引导的轮对与轴承复合故障诊断方法

针对列车轮对轴承系统复合故障难以辨识与诊断问题,提出一种变分模态分解(variational mode decomposition,VMD)引导的多故障特征提取匹配方法.首先,为避免预定义模式数在运行过程中对先验知识依赖从而对诊断结果造成影响,对原始轴箱振动数据进行逐阶VMD分解,模式数为2~N;其次,对VMD分解获取的本征模态函数(VMD intrinsic mode functions,VIMF)进行相关峭度计算,提取相关峭度最大的VIMF;然后,将相关峭度最大的VIMF进行平方包络分析,提取故障特征频率;最后,将所提方法与快速峭度谱、相关峭度谱方法进行对比.仿真信号和试验数据分析表明:所提方法完全规避了VMD模型中关键参数K的选择问题,可以准确、有效地分别提取出轮对和轴承的故障特征;与快速谱峭度与相关谱峭度方法相比,获取的故障特征谐波分量在数量和信噪比上均具有明显优势.

车轮扁疤激励下高铁轴箱系统振动特性研究

以某型高速列车轮对和轴箱轴承为研究对象,构建包含轮对轴箱轴承的车辆-轨道耦合动力学模型,研究在京津线轨道不平顺激扰及车轮扁疤激扰工况下轴箱系统内部结构的接触振动特性。结果表明:当车轮出现扁疤缺陷时会引起轴箱在垂向和横向的高频振动;随着车轮扁疤长度的增加,轴箱轴承滚子与外圈接触载荷高频段所占成分逐渐增加,引起轴承滚子与外圈的中高频激振,加速轴承的疲劳破坏;扁疤长度超过30 mm时,0号滚道区域的接触载荷变化较大,扁疤长度50 mm处轴箱轴承滚子与外圈接触载荷均值与扁疤长度10 mm处滚子与外圈接触载荷均值的最大值相比增加了33.38%;当列车运行速度在250 km/h左右时,车轮扁疤长度安全阈应限制在30 mm以内,尽量降低车轮较长扁疤引起的轮轨结构高频振动。

增强的最小相关广义Lp/Lq范数反卷积在旋转机械故障诊断中的应用

用于提取滚动轴承故障周期冲击特征的最小相关广义Lp/Lq范数反卷积(MCG-Lp/Lq-D)存在对先验周期参数的精确度要求过高的问题。因此有必要提出一种新的周期估计方法-具有约束的自适应周期估计(APEC),该方法可以在强噪声条件下依然能够稳定的给出周期信息的真实估计或其近似值,随后将APEC引入到MCG-Lp/Lq-D构造了新的盲解卷积算法EMCG-Lp/Lq-D,该方法不仅能在强噪声条件下通过APEC自适应调整故障周期,同时还继承了MCG-Lp/Lq-D对噪声和异常值鲁棒的特点。由于APEC是一种需要先验周期(不要求精确周期)指导的周期估计方法,这使得其在低信噪比(SNR)条件下具有更好的鲁棒性来估计故障周期,从而使EMCG-Lp/Lq-D的运用范围相较于MCG-Lp/Lq-D的更广泛。最后,仿真和实验验证了EMCG-Lp/Lq-D的有效性和优越性。

基于目标优化的移不变字典匹配追踪轴承故障诊断算法研究

滚动轴承作为一种关键旋转零部件,在高速列车上得到了广泛的应用。滚动轴承的故障诊断对维护列车的安全、舒适具有重要意义。在故障诊断过程中,实现早期微弱故障的探测以及并发故障的分离和提取至关重要。为此,提出了一种基于蜣螂优化算法的移不变字典匹配追踪算法。该算法采用预定义字典结构和循环提取的思想,首先,引入了蜣螂优化算法,并建立了一种基于相关峭度的新型目标优化函数,以此自适应构建预定义移不变结构的脉冲字典。同时,为了自适应获取匹配追踪框架中的最优稀疏度,提出了基于Hoyer指标的最优稀疏度获取准则。为了验证该算法的优越性,对高速列车传动系统中常见的齿轮箱轴承和轴箱轴承的故障信号进行了分析和对比。结果表明,该算法对早期微弱故障的检测具有更强的鲁棒性,同时对并发故障也具有较好的自适应检测能力,具有一定的工程应用价值。

Depositional process of hyperpycnal flow deposits:A case study on Lower Cretaceous Sangyuan outcrop in the Luanping Basin,Northeast China

Sedimentary process research is of great significance for understanding the distribution and characteristics of sediments.Through the detailed observation and measurement of the Sangyuan outcrop in Luanping Basin,this paper studies the depositional process of the hyperpycnal flow deposits,and divides their depositional process into three phases,namely,acceleration,erosion and deceleration.In the acceleration phase,hyperpycnal flow begins to enter the basin nearby,and then speeds up gradually.Deposits developed in the acceleration phase are reverse.In addition,the original deposits become unstable and are taken away by hyperpycnal flows under the eroding force.As a result,there are a lot of mixture of red mud pebbles outside the basin and gray mud pebbles within the basin.In the erosion phase,the reverse deposits are eroded and become thinner or even disappear.Therefore,no reverse grading characteristic is found in the proximal major channel that is closer to the source,but it is still preserved in the middle branch channel that is far from the source.After entering the deceleration phase,normally grading deposits appear and cover previous deposits.The final deposits in the basin are special.Some are reverse,and others are normal.They are superimposed with each other under the action of hyperpycnal flow.The analysis of the Sangyuan outcrop demonstrates the sedimentary process and distribution of hyperpycnites,and reasonably explain the sedimentary characteristics of hyperpycnites.It is helpful to the prediction of oil and gas exploration targets in gravity flow deposits.

Hydromassage of macular hole edges for large and persistent full-thickness macular holes

●AIM:To introduce the macular hole(MH)hydromassage technique as a potentially beneficial approach for the treatment of large or persistent MH.●METHODS:This retrospective observational case series comprised 16 consecutive patients(17 eyes)diagnosed with MH.Inclusion criteria involved a hole aperture diameter larger than 600μm or the presence of an unclosed MH larger than 600μm following the previous vitrectomy.Standard MH repair procedures were administered in all cases,involving the manipulation and aspiration of the hole margin through the application of water flow with a soft-tip flute needle.A comprehensive assessment was conducted for each case before and after surgery,and optical coherence tomography(OCT)images were captured at every follow-up point.●RESULTS:The mean preoperative aperture diameter was 747±156μm(range 611-1180μm),with a mean base diameter of 1390±435μm(range 578-2220μm).Following surgery,all cases achieved complete anatomical closure of MH,with 13 cases(76.5%)exhibiting type 1 closure and 4 cases(23.5%)demonstrating type 2 closure.No significant differences were observed in the preoperative OCT variables between the two closure types.Eyes with type 1 closure showed a significantly improved visual acuity(0.70±0.10,range 0.50-0.80)compared to those with type 2 closure(0.90±0.12,range 0.80-1.00,P=0.014).●CONCLUSION:The MH hydromassage technique demonstrates promising results,achieving acceptable closure rates in cases of large or persistent MH.This technique may serve as an effective adjunctive maneuver during challenging MH surgery.

稀疏性多源完全领域适配迁移诊断方法研究

高速列车在行驶过程中,其滚动轴承的工况往往会发生变化,如转向架的轴箱轴承转速变化等,在此情况下,传统的基于非平稳信号分析的滚动轴承故障诊断技术很难对故障进行有效检测。为了在变化的工况下实现故障类型的自适应识别,基于深度迁移学习的滚动轴承智能故障诊断技术逐渐被应用于轴承故障诊断领域中。然而,深度迁移学习智能故障诊断技术在工程应用中仍存在模型复杂度高的问题。此外,传统领域适配方法在进行迁移诊断时主要进行整体领域差异的对齐,忽略了不同域下同一故障状态的子域特征分布,导致模型的泛化能力差。同时,领域适配在滚动轴承智能故障诊断中的应用主要集中在单源领域,当源领域和目标领域数据分布差异过大时,单个源领域学习到的数据特征有限,可能无法达到较高的可迁移性。为改善上述问题,提出一种稀疏性多源完全领域适配迁移诊断方法,为验证所提算法的有效性,采用不同的故障数据建立不同的故障诊断场景并进行分析。结果表明,该方法中提出的周期循环稀疏设计模式使得卷积层和全连接层的权重矩阵包含大量规则排列的零权重参数,能够有效降低模型的复杂度。同时,该方法在进行数据特征的迁移时,考虑了全局和局部差异的对齐,能够一定程度改善模型的泛化能力。此外,通过不同数目源领域的试验验证分析,表明多源领域适配方法具有较好的迁移诊断效果,对于迁移诊断技术的实际应用具有一定的指导意义。

Microscopic oil occurrence in high-maturity lacustrine shales:Qingshankou Formation,Gulong Sag,Songliao Basin

Occurrence and mobility of shale oil are prerequisites for evaluating shale oil reserves and prioritizing exploration targets,particularly for heterogeneous lacustrine shales.The Qingshankou Formation in the Gulong Sag,Songliao Basin is a classic lacustrine pure shale reservoir that contains abundant shale oil resources.The predicted geological reserves of the shale are 1.268×10^(9) t.In this study,field emission scanning electron microscope(FE-SEM),the modular automated processing system(MAPS),pyrolysisgas chromatography(Py-GC),low-pressure nitrogen gas adsorption(LPNA),Soxhlet extraction,pyrolysis,and 2-D nuclear magnetic resonance(NMR)were integrated to describe the shale oil components,microscopic occurrence,mobility,and the effective pore size distribution.Meanwhile,the related controlling factors are discussed.The shale oil in the Qingshankou Fm exists dominantly in the matrix pores of the clay minerals,with small amounts distributed in the intergranular pores of terrigenous clastic grains,intercrystalline pores of pyrite,intragranular pores of ostracod shells,and micro-fractures.Shale oil is distributed in the pore spaces of variable sizes in different lithofacies.The clay mineral-laminated shales are characterized by the broadest range of pore size and largest volume of pore spaces with shale oil distribution,while the ostracod-laminated shales have limited pore spaces retaining oil.Furthermore,the proposed integrated analysis evaluates the shale oil molecules existing in two states:movable,and adsorbed oil,respectively.The result illustrates that movable oil takes up 30.6%e79.4%of the total residual oil.TOC,mineral composition,and pore structures of the shale joint together to control the states and mobility of the shale oil.TOC values are positively correlated with the quantities of shale oil regardless of the state of oil.The mineral components significantly impact the state of shale oil.Noticeable differences in the states of oil were observed following the changing types of minerals,possibly due to their difference in adsorption capacity and wettability.Clay minerals attract more adsorbed oil than movable oil.Felsic minerals generally decrease the occurrence of total and adsorbed oil.Carbonate plays a positive role in hydrocarbon retention of all the shale oil states.As for the pore structure,the average pore size exerts a critical impact on the total,movable,and adsorbed oil content.The total pore volume and specific surface area of shales play a principal role in controlling the total yields and amounts of adsorbed oil.This research improves the understanding of the occurrence characteristics and enrichment mechanisms of shale oil in terrestrial pure shales and provides a reference for locating favorable shale oil exploration areas.

轴承滚子缺陷激励下高铁轴箱系统振动特性研究

以某型高速列车转向架上轮对和轴箱系统为研究对象,构建一种包含轴箱轴承滚子缺陷的车辆-轨道耦合动力学模型,并利用现场试验数据验证轴箱轴承−车辆−轨道耦合动力学模型的有效性。通过仿真计算获得在京津线轨道随机不平顺激扰工况下轴箱的振动加速度时间历程以及轴承滚子与外圈的接触载荷时间历程,结合轴承滚子缺陷数学分析模型,研究轴承滚子缺陷激扰工况下轴箱系统内部结构的接触振动特性。研究结果表明:当轴承滚子出现缺陷时,轴箱横向和垂向振动加速度包络谱在滚子故障频率和2倍滚子故障频率的倍频处出现振动加速度峰值,且以保持架旋转频率10.32 Hz进行振幅调制;缺陷滚子与外圈接触载荷频谱主要分布在0~100 Hz的低频段,在200~1000 Hz频段内出现以轴承保持架旋转频率为频率间隔的一系列峰值;随着轴承滚子缺陷宽度的增加,滚子与外圈接触载荷中高频段所占成分逐渐增加,表明轴承滚子缺陷宽度的增加会逐渐引起轴承滚子与外圈的中高频激振,加强轴箱轴承内部构件之间的动态作用从而加速轴承的疲劳破损失效;列车运行速度在250 km/h左右时,仿真数据表明轴承滚子缺陷宽度需限制在1 mm以内,尽量减少因轴承滚子缺陷宽度过大而引起的滚子与外圈接触载荷升高造成结构疲劳等一系列问题。

延伸奇异值分解包及其在高速列车轮对轴承故障诊断中的应用

结合多分辨奇异值分解包的分解结构和对滚动轴承故障信号的Hankel矩阵的奇异值分布特性研究,提出了延伸奇异值分解包。该算法的核心包括矩阵递推构造和矩阵重构。以分量信号能量为指标,提出了有效分量信号的筛选准则,并基于该准则,进一步提出了延伸奇异值分解包的快速算法。仿真结果表明,延伸奇异值分解包对信号中共振频带分量信号具有很好的分解能力,方法具有强鲁棒性,同时极大地改善了奇异值分解包中出现的模态混叠。应用高速列车轮对轴承试验数据对该方法进行试验验证,结果表明,该方法能有效分离高速列车轮对轴承复合故障信号的不同共振频带信号,对筛选的有效分量信号进行包络分析,可有效提取不同类型的故障特征频率及其谐波,对共振频带的聚集性和故障的表征力相比奇异值分解包均有显著提高。

高速列车轴箱轴承多故障滚动体振动模型及其缺陷定位方法

针对传统时域分析方法识别滚动轴承故障滚动体数量和相位信息容易失效的问题,建立了存在多个故障滚动体的滚动轴承振动模型,并提出了基于包络谱和卷积平均思想的故障滚动体定位方法。所提模型综合考虑了包括轴承几何结构、轴转速、轴承载荷分布、传递函数、振动的指数衰减和滚动体随机滑动等多个因素。结合所提模型,推导出不同滚动体缺陷激发的最大冲击的时间间隔受缺陷在滚动体上的位置分布的影响,导致该时间间隔存在较大波动。阐述了传统时域分析中,采用最大冲击间隔定位故障滚动体容易失效的原因。应用高速列车轴箱轴承试验数据验证了所提模型的准确性和所提缺陷定位方法的有效性,结果表明,所提模型对理解滚动体故障轴承的振动机理和对设计具体的分析和诊断工具有所帮助,所提缺陷定位方法能有效识别故障滚动体的数量和间隔信息,相比传统时域分析方法,缺陷定位的效率和抗噪声干扰能力得到了显著提高。

高阶频率加权能量算子在列车轴箱轴承故障诊断中的应用

针对轴箱轴承振动信号中微弱故障冲击难以识别的问题,提出了高阶频率加权能量算子的信号解调方法,进而完成轴箱轴承的故障诊断。频率加权能量算子(FWEO)通过在解调时加入信号中瞬时频率的权重,从而提高了干扰情况下解调的鲁棒性,但是当干扰信号能量较大时,FWEO依然无法有效解调轴承的故障冲击信息。因此,在FWEO基础上通过高阶的导数运算,形成了高阶频率加权能量算子(HFWEO)。HFWEO通过高阶导数运算提高了瞬时频率的权重,从而有效提高了HFWEO对干扰信号的抑制作用;使用相关峭度准则确定合适的阶次,保证HFWEO在提高抗干扰性的同时又引入较少的高频噪声,从而实现更可靠的轴箱轴承故障诊断。使用所提出的解调方法对仿真信号与轴箱轴承振动信号进行解调,并与传统解调方法进行对比,结果表明,提出的HFWEO能量算子对干扰具有很好的抑制作用,可以在较低信号干扰比情况下具有良好的解调效果,同时所提的相关峭度准则可以准确地确定最佳的HFWEO阶次,在复杂干扰情况下依然可以有效提取轴承故障冲击,克服了传统解调方法在干扰严重时的局限性,抑制了干扰的影响,对信号中故障冲击识别更加有效,为更准确、快速判断轴承故障类型提供了可靠保证。

车轮柔性化对高铁轴箱轴承振动特性分析

轴箱轴承作为高速列车旋转系统中最为重要的部件之一,其运行环境恶劣,探究轴箱轴承在恶劣运行工况下的动力学行为是保证高铁安全运行亟待解决的问题。以正在运营的某型高速列车转向架上轮对和轴箱轴承为研究对象,构建一种包含柔性轮对的轴箱轴承-车辆-轨道耦合动力学模型,通过数值和有限元计算,研究在京津线轨道激扰下轴箱轴承内部结构的接触振动特性。研究结果表明:轨道激扰对滚子与外圈的接触载荷影响较大;刚性轮对和柔性轮对计算滚动体与外圈的接触力基本相同,且随着车辆运行,接触载荷呈周期性变化;柔性轮对导致滚动体与外滚道之间的中高频碰撞增加;双列圆锥滚子轴承的第1列轴承和第2列轴承交替承载,第1列轴承承受主要载荷,第2列轴承辅助承载;刚性轮对计算外圈垂向振动加速度最大峰值远大于柔性轮对所计算得到的振动加速度最大峰值,相对刚性轮对而言,柔性轮对的变形能够减弱轮轨间的刚性约束关系,更切实地反映实际运营工况下的轮轨耦合振动关系。

Designing Advanced Aqueous Zinc-Ion Batteries:Principles,Strategies,and Perspectives

Aqueous zinc-ion batteries(AZIBs)are an appealing battery system due to their low cost,intrinsic safety,and environmental-friendliness,while their application is plagued by the obstacles from the cathode,electrolyte,and zinc anode.Summarizing the design principles and strategies toward the optimization of cathode,electrolyte,and zinc anode is crucial for the development of AZIBs.Herein,we present a comprehensive analysis of the design principles and promising strategies toward the improvement of AZIBs.Firstly,the various reaction mechanisms are summarized and the existing issues associated with the cathode,electrolyte,and zinc anode are discussed to guide the rational design of AZIBs.Subsequently,we provide an in-depth and comprehensive discussion on the design principles and strategies for the electrodes/electrolyte/separator optimization,and analyze the advantages and disadvantages of various strategies.Importantly,the design principles and strategies of the newly appeared conversion-type AZIBs,such as Zn-S battery and Zn-Se battery,are also discussed and analyzed.The effect of design strategies on the electrochemical performance and the relationship between the current issues and strategies are also unveiled in detail.Finally,some research trends and perspectives are provided for designing better AZIBs.

Expression of Wnt and NCX1 and its correlation with cardiomyocyte apoptosis in mouse with myocardial hypertrophy

Objective:To study the correlation between expression of Wnt and NCXl and cardiomyocyte apoptosis in mouse with myocardial hypertrophy.Methods:C57B/16 male mice were given the subcutaneous injection of 1 mg/kg isoprenaline to build the myocardial hypertrophy model.After 14 d of model building,mice were executed by cervical vertebra luxation.The ratio of heart weight/body weight(HW/BW) and heart weight/tibia length(HW/TL) was observed and proved using HE staining mat detected the size of eaidiomyocytes.40 male C57B/16 mice were randomly divided into the sham group(normal saline) and model group(isoprenaline),with 20 mice in each group.The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling was applied to detect the cardiomyocyte apoptosis;while Western blot and immunohistochemistry were employed to detect the expression of Wnt and NCX1.Meanwhile,the correlation between these two proteins and cardiomyocyte apoptosis was explored.Results:Compared with the sham group,the ratio of HW/BW and HW/TL was increased in the model group,as well as the bigger and hypertrophied cardiomyocytes,decreased number and increased apoptosis of eaidiomyocytes,and increased positive expression of Wnt3 a,WntSa and NCXl in the cardiac muscle tissue.Besides,there was positive correlation between the expression of Wnt and NCXl and the cardiomyocyte apoptosis.Conclusions:The expression of Wnt3 a,Wnt5a and NCXl in mouse with myocardial hypertrophy is increased and positively correlated with the cardiomyocyte apoptosis.

Sm-Nd dating and rare earth element geochemistry of the hydrothermal calcites from Guling carbonate-hosted talc mineralization in the central Guangxi province,South China

Many carbonate-hosted talc mineralization,which are widespread in South China,exclusively developed in Carboniferous dolomitic limestone with many siliceous bands and nodules,and cherts.One of those typical deposits is the Guling talc deposit in Mashan County,central Guangxi province,with a talc reserve of1.51 million tons.Mineral associations in the deposit are sample,mainly including talc and calcite.In this paper,Sm-Nd isotopic system and rare earth elements and yttrium(REE + Y) for the hydrothermal calcite intergrown with talc are used to constrain the age and origin of the talc mineralization.The hydrothermal calcite samples from the deposit display Sm and Nd concentrations ranging from 0.18 to 0.85 and 0.85 to 4.56 ppm,respectively,and variable Sm/Nd ratios of 0.21-0.24.These calcites further yield an Sm-Nd isochron age of 232 ±19 Ma(2a)(MSWD = 0.47) with an concordant initial ^(143)Nd-^(144)Nd ratios of 0.511967 ± 0.000017,which should be interpreted as the mineralization age of the Guling talc deposit.In addition,the calcite samples are enriched in REE with the variable SREE contents ranging from 4.82 to21.50 ppm and display relatively consistent chondritenormalized REE + Y patterns with the LREE enrichment(LREE/HREE=2.00-3.60)and the obvious negative Eu(δEu=0.52-0.68)and Ce(δCe=0.16-0.33)anomalies.The Y/Ho ratios of seven calcites varies from 43.30 to59.34,with a mean value of 49.73.The available mineral associations and REE parameters(i.e.,REE patterns and Y/Ho ratios) of those calcites indicate that the ore-forming fluids of the talc mineralization be probably derived from the meteoric waters,in particular evolved ones in the Karst areas and the ore-forming materials(e.g.,Si and Mg) are likely to be originated from the ore-bearing dolostone in the Yanguan Formation(C_1y) and underlying siliceous rocks in the Liujiang Formation(D_3l).Furthermore,the talc mineralization could take place within a hydrothermal system with relative oxidizing environment and middle temperature,due to the obvious negative Eu and Ce anomalies in the calcites in the Guling deposit.

The occurrence state of vanadium in the black shale-hosted vanadium deposits in Shangling of Guangxi Province, China

The Shangling vanadium deposit, which occurs in the Lower Devonian Tangding formation black rock series strata, has V2O5 reserves of more than 1.5 million tons and prospective reserves of more than 2 million tons. Preliminary studies on the occurrence state of vanadium(V) in this deposit have been conducted by artificial heavy minerals concentrates, leaching experiments, scanning and transmission electron microscopy and X-ray powder diffraction.These experiments have revealed no independent vanadium mineral occurrences in the Shangling vanadium deposit and the percentages of water-soluble vanadium, hydrochloric acid soluble vanadium and HF soluble vanadium were1.93 %, 21.42 % and 76.47 %, respectively. Based on our data and earlier research, we estimate that the valences state of V absorbed onto the surface of organic matter or clastic particles are +5 and +4, accounting for 10.00 % and13.35 % of the total amount of V, respectively and the valences state of V that exist in the octahedral crystal lattice of authigenic illite include +3 and +4, accounting for71.64 % and 4.83 % of the total amount of V, respectively.By calculating the correlation between the total organic carbon and V, we infer that after deposition and before entering the crystal lattice of illite, V occurs in the form of humate complex or is adsorbed by organic matter. About4.24 % of the Al is in the octahedral crystal lattice of illite,which was replaced by the vanadium under the metallogenic environments of Shanglin.

自适应谱峭度图及其在滚动轴承故障诊断中的应用

提出了一种新的自适应谱峭度图方法。首先采用CEEMDAN方法分解信号的傅里叶频谱,然后对得到的低频IMF分量与残差项进行分层累加计算,对每一层的频谱趋势寻找极小值点,使其作为频谱划分边界,将划分后的各频段通过正交滤波器并利用峭度指标对划分后信号中的故障信息进行评估,构造出一种新的自适应谱峭度图。该方法能够克服快速谱峭度图因遵循固定划分规则易使检测出的频带不能包含完整的故障信息或是提取到无效分量的情况,并且分别利用轴承外圈故障的仿真信号和试验信号,验证了该方法的有效性。

Recent advances in generation of terahertz vortex beams andtheir applications

Last decade has witnessed a rapid development of the generation of terahertz(THz)vortex beams as well as their wide applications,mainly due to their unique combination characteristics of regular THz radiation and orbital angular momentum(OAM).Here we have reviewed the ways to generate THz vortex beams by two representative scenarios,i.e.,THz wavefront modulation via specific devices,and direct excitation of the helicity of THz vortex beams.The former is similar to those wavefront engineering devices in the optical and infrared(IR)domain,but just with suitable THz materials,while the latter is newly-developed in THz regime and some of the physical mechanisms still have not been explained explicitly enough though,which would provide both challenges and opportunities for THz vortex beam generation.As for their applications,thanks to the recent development of THz optics and singular optics,THz vortex beams have potentials to open doors towards a myriad of practice applications in many fields.Besides,some representative potential applications are evaluated such as THz wireless communication,THz super-resolution imaging,manipulating chiral matters,accelerating electron bunches,and detecting astrophysical sources.