Research on digital twin technology and its application in intelligent operation and maintenance of highspeed railway infrastructure

Purpose–This paper analyzes the application of digital twin technology in the field of intelligent operation and maintenance of high-speed railway infrastructure from the perspective of top-level design.Design/methodology/approach–This paper provides a comprehensive overview of the definition,connotations,characteristics and key technologies of digital twin technology.It also conducts a thorough analysis of the current state of digital twin applications,with a particular focus on the overall requirements for intelligent operation and maintenance of high-speed railway infrastructure.Using the Jinan Yellow River Bridge on the Beijing–Shanghai high-speed railway as a case study,the paper details the construction process of the twin system from the perspectives of system architecture,theoretical definition,model construction and platform design.Findings–Digital twin technology can play an important role in the whole life cycle management,fault prediction and condition monitoring in the field of high-speed rail operation and maintenance.Digital twin technology is of great significance to improve the intelligent level of high-speed railway operation and management.Originality/value–This paper systematically summarizes the main components of digital twin railway.The general framework of the digital twin bridge is given,and its application in the field of intelligent operation and maintenance is prospected.

Application Strategies of Spatial Refinement Design in Ancient Cities Supported by Digital Te-Zhaoyu Ancient City in Qixian County as an Example

Digital technology provides a method of quantitative investigation and data analysis for contemporary landscape spatial analysis,and related research is moving from image recognition to digital algorithmic analysis,providing a more scientific and macroscopic way of research.The key to refinement design is to refine the spatial design process and the spatial improvement strategy system.Taking the ancient city of Zhaoyu in Qixian County,Shanxi Province as an example,(1)based on obtaining the integrated data of the ancient city through the drone tilt photography,the style and landscape of the ancient city are modeled;(2)the point cloud data with spatial information is imported into the point cloud analysis platform and the data analysis is carried out from the overall macroscopic style of the ancient city to the refinement level,which results in the formation of a more intuitive landscape design scheme,thus improving the precision and practicability of the landscape design;(3)Based on spatial big data,it starts from the spatial aggregation level,spatial distribution characteristics and other evaluation index system to achieve the refinement analysis of the site.Digital technology and methods are used throughout the process to explore the refined design path.

ValueofDigitalX—RayPhotographyinDiagnosisofCongenitalHeartDisease

目的探讨数字化X线摄影在先天性心脏病诊断中的应用价值。方法收集我院2009-01-01—10-31经数字化X线摄影检查阳性并经临床随访或手术证实的先天性心脏病患者97例,对其临床及影像学资料进行回顾性分析。结果 97例患者中,房间隔缺损46例（47.4%）,动脉导管未闭17例（17.5%）,室间隔缺损13例（13.4%）,法洛四联症5例（5.2%）,肺动脉瓣狭窄3例（3.1%）,镜面右位心4例（4.1%）,右位主动脉弓7例（7.2%）,其他复杂畸形2例（2.1%）。X线表现为：肺血增多、肺血减少及心影形态失常。结论数字化X线摄影准备简单、安全、快捷,禁忌证少,整体感强,同时还是术后随访的重要检查手段,目前仍然能够为先天性心脏病的诊断提供独特和有价值的信息。

Full-field mapping of internal strain distribution in red sandstone specimen under compression using digital volumetric speckle photography and X-ray computed tomography

It is always desirable to know the interior deformation pattern when a rock is subjected to mechanicalload. Few experimental techniques exist that can represent full-field three-dimensional （3D） straindistribution inside a rock specimen. And yet it is crucial that this information is available for fully understandingthe failure mechanism of rocks or other geomaterials. In this study, by using the newlydeveloped digital volumetric speckle photography （DVSP） technique in conjunction with X-ray computedtomography （CT） and taking advantage of natural 3D speckles formed inside the rock due to materialimpurities and voids, we can probe the interior of a rock to map its deformation pattern under load andshed light on its failure mechanism. We apply this technique to the analysis of a red sandstone specimenunder increasing uniaxial compressive load applied incrementally. The full-field 3D displacement fieldsare obtained in the specimen as a function of the load, from which both the volumetric and the deviatoricstrain fields are calculated. Strain localization zones which lead to the eventual failure of the rock areidentified. The results indicate that both shear and tension are contributing factors to the failuremechanism. 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

A Model for Estimating Total Forest Coverage with Ground-Based Digital Photography

Vegetation fractional coverage (VFC) is one of the key indicators of vegetation distribution. In the work a measurement-based model was developed to derive total forest VFC (TG) as well as the VFC of trees (T) and shrub-grasses (G) separately in a subtropical forest area in Nanjing, China. Both upward and downward photographs were taken with a digital camera in 72 quadrats (10 m × 10 m each). Fifteen models were established and validated. Models jointly using both T and G performed better than those using the T and G separately. The best model, TG = T + G- 1.134 × T × G- 0.025 (R2 = 0.9115, P < 0.01, root mean squared error = 0.0789), is recommended for application. This model provides a good way to obtain total forest VFC values through taking tree and shrub-grass photos on ground below tree canopy rather than above tree canopy.

PIV analysis and high-speed photographic observation of cavitating flow field behind circular multi-orifice plates

Based on a self-developed hydrodynamic cavitation device with different geometric parameters for circular multi-orifice plates,turbulence characteristics of cavitating flow behind multi-orifice plates,including the effects of orifice number and orifice layout on longitudinal velocity,turbulence intensity,and Reynolds stress,were measured with the particle image velocimetry(PIV)technique.Flow regimes of the cavitating flow were also observed with high-speed photography.The experimental results showed the following:(1)high-velocity multiple cavitating jets occurred behind the multi-orifice plates,and the cavitating flow fields were characterized by topological structures;(2)the longitudinal velocity at each cross-section exhibited a sawtooth-like distribution close to the multi-orifice plate,and each sawtooth indicated one jet issuing from one orifice;(3)there were similar magnitudes and forms for the longitudinal and vertical turbulence intensities at the same cross-section;(4)the variation in amplitude of Reynolds stress increased with an increase in orifice number;and(5)the cavitation clouds in the flow fields became denser with the increase in orifice number,and the clouds generated by the staggered layout of orifices were greater in number than those generated by the checkerboard-type one for the same orifice number.The experimental results can be used to analyze the mechanism of killing pathogenic microorganisms through hydrodynamic cavitation.

Analysis of droplet transfer of pulsed MIG welding based on electrical signal and high-speed photography

In order to study how welding parameters affect welding quality and droplet transfer, a synchronous acquisition and analysis system is established to acquire and analyze electrical signal and instantaneous images of droplet transfer simultaneously, which is based on a self-developed soft-switching inverter. On the one hand, welding current and voltage signals are acquired and analyzed by a self-developed dynamic wavelet analyzer. On the other hand, images are filtered and optimized after they are captured by high-speed camera. The results show that instantaneous waveforms and statistical data of electrical signal contribute to make an overall assessment of welding quality, and that optimized high-speed images allow a visual and clear observation of droplet transfer process. The analysis of both waveforms and images leads to a further research on droplet transfer mechanism and provides a basis for precise control of droplet transfer.

Evaluating the impact of sampling schemes on leaf area index measurements from digital hemispherical photography in Larix principis-rupprechtii forest plots

Background:Digital hemispherical photography(DHP)is widely used to estimate the leaf area index(LAI)of forest plots due to its advantages of high efficiency and low cost.A crucial step in the LAI estimation of forest plots via DHP is choosing a sampling scheme.However,various sampling schemes involving DHP have been used for the LAI estimation of forest plots.To date,the impact of sampling schemes on LAI estimation from DHP has not been comprehensively investigated.Methods:In this study,13 commonly used sampling schemes which belong to five sampling types(i.e.dispersed,square,cross,transect and circle)were adopted in the LAI estimation of five Larix principis-rupprechtii plots(25m×25 m).An additional sampling scheme(with a sample size of 89)was generated on the basis of all the sample points of the 13 sampling schemes.Three typical inversion models and four canopy element clumping index(Ωe)algorithms were involved in the LAI estimation.The impacts of the sampling schemes on four variables,including gap fraction,Ωe,effective plant area index(PAIe)and LAI estimation from DHP were analysed.The LAI estimates obtained with different sampling schemes were then compared with those obtained from litter collection measurements.Results:Large differences were observed for all four variable estimates(i.e.gap fraction,Ωe,PAIe and LAI)under different sampling schemes.The differences in impact of sampling schemes on LAI estimation were not obvious for the three inversion models,if the fourΩe algorithms,except for the traditional gap-size analysis algorithm were adopted in the estimation.The accuracy of LAI estimation was not always improved with an increase in sample size.Moreover,results indicated that with the appropriate inversion model,Ωe algorithm and sampling scheme,the maximum estimation error of DHP-estimated LAI at elementary sampling unit can be less than 20%,which is required by the global climate observing system,except in forest plots with extremely large LAI values(~>6.0).However,obtaining an LAI from DHP with an estimation error lower than 5%is impossible regardless of which combination of inversion model,Ωe algorithm and sampling scheme is used.Conclusion:The LAI estimation of L.principis-rupprechtii forests from DHP was largely affected by the sampling schemes adopted in the estimation.Thus,the sampling scheme should be seriously considered in the LAI estimation.One square and two transect sampling schemes(with sample sizes ranging from 3 to 9)were recommended to be used to estimate the LAI of L.principis-rupprechtii forests with the smallest mean relative error(MRE).By contrast,three cross and one dispersed sampling schemes were identified to provide LAI estimates with relatively large MREs.

Development of High-Speed On-Of Valves and Their Applications

With the widespread application of the computer and microelectronic technology in the industry,digitization becomes the inevitable developing trend of the hydraulic technology.Digitization of the hydraulic components is critical in the digital hydraulic technology.High-speed on-of valves(HSVs)which convert a train of input pulses into the fast and accurate switching between the on and of states belong to widely used basic digital hydraulic elements.In some ways,the characteristics of the HSVs determine the performance of the digital hydraulic systems.This paper discusses the development of HSVs and their applications.First,the HSVs with innovative structures which is classifed into direct drive valves and pilot operated valves are discussed,with the emphasis on their performance.Then,an overview of HSVs with intelligent materials is presented with considering of the switching frequency and fow capacity.Finally,the applications of the HSVs are reviewed,including digital hydraulic components with the integration of the HSVs and digital hydraulic systems controlled by the HSVs.

A survey of high-speed high-resolution current steering DACs

Digital to analog converters(DAC)play an important role as a bridge connecting the analog world and the digital world.With the rapid development of wireless communication,wideband digital radar,and other emerging technologies,better performing high-speed high-resolution DACs are required.In those applications,signal bandwidth and high-frequency linearity often limited by data converters are the bottleneck of the system.This article reviews the state-of-the-art technologies of high-speed and high-resolution DACs reported in recent years.Comparisons are made between different architectures,circuit implementations and calibration techniques along with the figure of merit(FoM)results.

Mirror-assisted multi-view high-speed digital image correlation for dual-surface dynamic deformation measurement

Based on the recently proposed mirror-assisted multi-view digital image correlation(MV-DIC),we establish a cost-effective and easy-to-implement mirror-assisted multi-view high-speed digital image correlation(MVHS-DIC)method and explore its applications for dual-surface full-field dynamic deformation measurement.In contrast to the general requirement of four expensive high-speed cameras for dual-surface dynamic deformation field measurement,the established mirror-assisted MVHS-DIC halves the cost by involving only two synchronized high-speed cameras and two planar mirrors.The two synchronized high-speed cameras can dynamically measure the front and rear surfaces of a sheet sample simultaneously through the reflection of the two mirrors.The results on the two surfaces are then transformed into the same coordinate system,leading to the required dual-surface 3D dynamical deformation fields.The effectiveness and accuracy of the established system are validated through modal tests of a cantilever aluminum sheet.The vibration measurement of a drum and dual-surface transient deformation measurement of a smartphone in the drop-collision process further prove its practicability.Benefiting from the attractive advantages of multi-view dynamic deformation measurement in a cost-efficient way,the established mirror-assisted MVHS-DIC is expected to encourage more comprehensive dynamic mechanical behavior characterization of regular-sized materials and structures in vibration and impact engineering fields.

Photo Socialization in Digital Natives

In the following work of research, we shall present the results of a study on forms of digital photographic socialization as carried out by the so-called ＂digital natives＂ in order to explore their competence in managing digital photographic output and cultural practices. This shall be done under the following categories of analysis： snapshot, organization, socialization, reception, privacy, and copyrights in digital photography. The study explores the forms of digital photography production, technical problems of photographic management and the final uses that digital photographers give to their photos in terms of web tools 2.0, mobile telephones and social networks. Digital photography technology, compact cameras, mobile phones with cameras, specialized websites in photography and the lnternet generate new forms of production and emerging styles of digital photographic socialization. The study is carried out using a defined sample of university students, those digital natives who create and use digital photography.

Algorithm implementation of high-speed laser g yro signal demodulation filter

Based on the characteristics of field-programmable gate array(FPGA) such as multi-task,high-speed,parallelity,etc,a filtering algorithm is presented to filter the output signal of laser gyr o with high-speed and high accuracy.The filter is composed of basic logic cell s,multipliers an d memory inside FPGA.By using an multiplication decomposition method and design ing reliable time-sequence,the filter is realized,which is easy to be transpl anted and of low cost.Furthermore,all the signal demodulation algorithms of t he laser gyr oscope can be integrated in only one FPGA,which reduces the cost and complexity of the system.

DIP付费对医疗服务项目诊疗强度的影响研究

目的:探索DIP付费对医疗服务项目诊疗强度的影响。方法:收集某市2020年1月至2022年12月330家医疗机构住院患者开展数字化摄影诊疗的数据,利用独立样本t检验比较诊疗强度的变化,采用间断时间序列分析考察DIP付费对诊疗强度的影响。结果:DIP付费后三级医院、一级医院数字化摄影诊疗强度分别增加了0.03和0.04,二级医院下降了0.06;三级医院诊疗强度在短期内增加(β_(2)=0.061),长期却呈现下降趋势(β_(3)=-0.007)。结论:DIP付费对医疗服务项目诊疗强度的政策效应可能与政策预期不一致,异质性和同质性并存;要强化DIP支付方式改革与医疗服务价格改革的协同路径。

基于不同数据源的数字孪生小流域底板模型精度检验

为解决小流域综合治理规划设计中基础地形数据获取困难等问题,基于合成孔径雷达卫星遥感影像、倾斜摄影影像、光探测测距影像等3种主流遥感数据源,分别建立栖龙湾小流域数字孪生底板模型,进而提取主沟道纵断面、2块梯田样地边界、10个林地样区的郁闭度,与人工解译和实测结果对比进行精度检验,结果表明:以光探测测距影像为数据源的提取精度最高,以倾斜摄影影像为数据源的提取精度次之,以孔径雷达卫星遥感影像为数据源的提取精度最低。鉴于3种数据源小流域底板模型各有优缺点,可根据实际工作需要进行多源数据融合,以改善数字孪生技术在小流域综合治理规划设计中的应用效果。在栖龙湾小流域内选择石坎梯田地块进行合成孔径雷达卫星遥感影像与倾斜摄影影像数据融合、选择科普展览馆进行倾斜摄影影像与光探测测距影像数据融合,均取得良好的效果。

基于数字孪生的烟田管理系统

烟草农业已通过实施设施农业和全程机械化等手段来提升烟叶的生产效率、烘烤烟草的品质以及农民的收益,但在烟田管理上仍然面临由非线性、互馈性、多尺度等难题带来的效率低下问题。采用数字孪生理论和技术,以昆明地区的烟田管理系统为研究对象,设计多要素物联网数据采集装置,结合无人机倾斜摄影技术,建立一种以虚控实的数字化在线推理和反馈体系的烟田数字模型,以烟草氮元素管理为实践应用,实现了数据驱动的烟田农事管理。结果表明,数字孪生技术能显著提升烟草农业的管理效率,其中氮元素管理服务效率提升71%。数字孪生技术在烟田管理的全过程中都有广泛的应用潜力,为烟草农业的数字化转型提供应用参考。

超广角视网膜激光扫描成像系统在DR筛查中的应用评价

目的评价超广角视网膜激光扫描成像(UWFSLO)在糖尿病视网膜病变(DR)筛查中的应用价值。方法采用横断面研究,选取2016年10—12月在河北省唐山市开滦康复医院行DR筛查的2型糖尿病患者1288例2304眼,收集患者一般信息,完成UWFSLO和45°水平两视野数字彩色眼底照相检查,比较DR的检出及分级水平。不同眼底检查对DR分级的一致性采用Cohen Kappa检验。结果去除成像不清晰及缺失的图像,最终1857眼纳入分析。彩色眼底照相、UWFSLO复合彩色图像及绿通道图像对DR的检出率分别为31.3%(581/1857)、44.5%(826/1857)和43.4%(807/1857),差异有统计学意义(χ^(2)=85.547,P<0.001),其中UWFSLO复合彩色图像、绿通道图像对DR的检出率均高于彩色眼底照相,差异均有统计学意义(均P<0.001)。45°水平两视野数字彩色眼底照相与UWFSLO复合彩色图像在DR检出分级之间的一致性一般,Kappa值为0.375(P<0.001),完全一致性为64.08%。UWFSLO绿通道图像与复合彩色图像对DR分级的一致性极好,Kappa值为0.953(P=0.008),完全一致性为98.17%。UWFSLO复合彩色图像对微动脉瘤(MA)、视网膜内微血管异常(IRMA)、视网膜新生血管(NV)病变的检出水平均低于绿通道图像,差异均有统计学意义(Z=-16.489、-4.198、-2.111,均P<0.05)。结论UWFSLO较45°水平两视野数字彩色眼底照相对DR的检出及分级评估水平更高,其中绿通道图像在MA、IRMA和小的NV病变检出上更为出色。在大规模人群DR的筛查及诊断中,UWFSLO具有较好的应用价值。

面向智慧城市的数字孪生实景三维建模方法研究

以某市的实景三维建模项目为例,研究探讨了基于无人机倾斜摄影技术构建实景三维模型的方法。通过使用飞马V10搭载D-OP4000倾斜模块,获取项目区的影像数据作为数据源,借助Context Capture和DP-Modeler等倾斜摄影后处理软件系统,进行实景三维的构建,并按照行业现行标准对所构建的实景三维模型进行质检和评估。结果表明,构建的实景三维模型达到了所需的精准度,有效地提升了数字孪生城市数字化建设的效率,为智慧城市动态景观生态的可持续发展提供重要的基础支撑。

基于多视角三维航摄影像的树高提取方法比较

树高是一个重要的立木调查因子,传统树高测量方法是利用测高器人工测量,该方法调查速度慢,效率低下.重叠的立体像对,可以反映地物的高度信息,为大面积树高信息提取提供了可能.本研究采用大疆Phantom 4 RTK无人机获取研究区航摄影像并构建立体像对,分别从不同视角采用三维模型直接测量法、倾斜摄影点云提取法、冠层高度模型局部最大值法进行了树高信息提取.研究结果表明,三种方法林木检测率依次为:82.5%、76.8%、71.1%,测得的树高结果精度分别为:R2=0.730,RMSE=1.699;R2=0.804,RMSE=1.459;R2=0.766,RMSE=1.548.三维模型测量法获取的树高提取率最高,倾斜摄影点云提取的树高值与实测值的拟合度最高.研究结果利用航摄影像能够高效地提取树高信息,为林业研究调查提供一种低成本、高效率的方法.

微距拍摄条件下的裂缝二维变化测量算法

结构性裂缝变化是建筑结构中常见的病害种类。针对微距拍摄下现有裂缝二维检测技术不足的问题,本文根据裂缝变化等效物理模型设计了一种能够适应微距拍摄的标靶,并提出了裂缝二维变化检测算法。本文算法由标靶靶别定位、畸变参数修正、裂缝参数计算等部分构成,由树莓派及摄像头组合形成微距图像采集装置,并基于室内试验验证。结果表明,该算法在微距拍摄下裂缝宽度变化测量精度在0.1 mm以内。