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Analytical Solutions of Cracks Emanating from an Elliptic Hole in an Infinite Plate under Tension

Chinese Journal of Mechanical Engineering 2014年第5期27卷 1057-1063页

作者： LIU Shuhong DUAN Shijie Department of Engineering Mechanics Shijiazhuang Tiedao University The Key Laboratory for Health Monitoring and Control of Large Structures of Hebei Province Department of Adult Education Shijiazhuang Tiedao University

It is a common phenomenon that the cracks originating from a hole can cause structural damage in ***,the fracture mechanics studies of hole edge crack problems are not *** problem of an elliptical hole with two collinear edge cracks of unequal length in an infinite plate under uniform tension at infinity is *** on the complex variable method,the analytical solutions of stress functions and stress intensity factors are *** stress distribution along the axes and the edge of the elliptical hole is given *** numerical results show that there is obvious stress concentration near the hole and cracks,and the stresses tend to applied loads at distances far from the defect,which conform to Saint-Venant’s ***,the stress functions are proved to be *** special conditions,the present configuration becomes the Griffith crack,two symmetrical cracks emanating from an elliptical hole,two cracks of unequal length emanating from a circular hole,a crack at the edge of a circular hole,or a crack emanating from an elliptical *** with available results,stress intensity factors for these special shapes of ellipses and cracks show good *** stress intensity factor for two cracks of unequal length at the edge of an elliptical hole increases with the crack length and the major-to-minor axis ratio of the elliptical *** stress distribution in an infinite plate containing an elliptic hole with unsymmetrical cracks is given for the first time.

关键词： hole crack stress distribution stress intensity factor

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Effective intrusion detection for railway scene based on video analytics 8

Effective intrusion detection for railway scene based on vid...

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8th International Conference on Structural health monitoring of Intelligent Infrastructure, SHMII 2017

作者： Li, Y.D. Lin, Y.B. Zhang, C. Zhao, W.G. School of Electronic and Information Engineering North China University of Technology Beijing100041 China Key Laboratory for Health Monitoring and Control of Large Structures Shijiazhuang050043 China Institute of Structure Health Monitoring and Control Shijiazhuang Tiedao University Shijiazhuang050043 China

ISBN: (纸本)9781925553055

Intrusion detection for railway scene is the essential method to avoid railway accidents caused by the invasions of pedestrians, falling rocks, animals, etc. In this paper, an automatic computer-vision based scheme is proposed to detect abnormal events in the track area, and send pre-warning signals to the control center. First, background is estimated by Gaussian mixture models, and the targets are obtained from the difference image between foreground and background combining with threshold, morphological filtering and connected component labeling. Second, mean shift algorithm is used to track the invasive target. To improve the tracking robustness, Histogram of Oriented Gradient (HOG) is chosen as the feature space to establish the target model, which has strong discriminative ability and robustness over illumination variation and small distortion of object. Third, behavior analysis is conducted based on target trajectory to determine whether there exist abnormal events in the track area. If yes, alarm messages with high-definition pictures are sent to control center. The proposed method has been operated on K141 spot of Shuohuang railway. The practical running results show that the intrusion detection system is effective and robust in railway scene. © 2017 International Society for Structural health monitoring of Intelligent Infrastrucure. All rights reserved.

关键词： Intrusion detection

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Experimental and numerical studies on the buoyancy-driven smoke movement in inclined short tunnel fires under natural ventilation

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Tunnelling and Underground Space Technology 2025年 163卷

作者： Guo, Qinghua Yan, Zhiguo Xi, Baoping Li, Xingli Zhang, Yao School of Safety and Emergency Management Engineering Taiyuan University of Science and Technology 66 Waliu Road Taiyuan030024 China State Key Laboratory of Disaster Reduction in Civil Engineering Tongji University 1239 Siping Road Shanghai200092 China College of Mining Engineering Taiyuan University of Technology 18 West Xin Kuangyuan Road Taiyuan030024 China Key Laboratory of Large Structure Health Monitoring and Control Shijiazhuang050043 China

The paper focuses on the smoke flow movement in inclined short tunnel fires. Small-scale tunnel fire tests and numerical simulations are implemented by considering the tunnel inclination, heat release rate (HRR), tunnel height and upward distance from fire source to upward opening. The comprehensive impacts of tunnel inclination, HRR and upward length on the smoke back-layering flow and the influencing mechanism are emphasized. It is found that as the upward distance and tunnel inclination increase, the back-layering length decreases, and at the meantime, the decrease rate is affected by the HRR. Specifically, under a certain tunnel inclination, as the upward distance increases, the back-layering length decreases faster as HRR becomes greater. Besides, as the tunnel inclination increases, the decrease rate of the back-layering length against the upward distance also becomes greater under a larger HRR. Meanwhile, it is found that when the fire is located near the upward opening, back-layering length becomes longer as HRR increases, however, the increase trend levels off as the tunnel becomes steeper. This leads to the results that the back-layering length may increase, level off and decrease with HRRs. Based on these findings, a prediction correlation for the back-layering length is established considering multi-factors (tunnel inclination, upward length, HRR and tunnel height). Furthermore, the verification is implemented by comparing the calculated back-layering length and test and numerical simulation results, showing an acceptable prediction. © 2025 Elsevier Ltd

关键词： Buoyancy

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Analysis of transverse thermal regime difference of high-speed railway roadbed in seasonally frozen regions 15

Analysis of transverse thermal regime difference of high-spe...

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15th International Conference of the International Association for Computer Methods and Advances in Geomechanics, IACMAG 2017

作者： Zhang, Yuzhi Wen, An Cheng, Boyuan Key Laboratory for Health Monitoring and Control of Large Structures in Hebei Province Shijiazhuang Tiedao University Shijiazhuang Hebei050043 China

The transverse thermal regime differences are widespread for high-speed railway roadbed in seasonally frozen regions. Based on the monitored data of four typical roadbed sections from Harbin-Dalian high-speed railway in seasonally frozen regions of China, the external influence and heat absorption of roadbed different parts are studied quantitatively through the comparisons of the temperature amplitude and average temperature, and then the characteristics of the frost penetration development are analyzed. The temperature variation laws of the coldest and hottest months with depth are also analyzed. On the basis of the above analysis, the influence factors and potential hazards of the transverse differences are discussed. It is stated that: the west shoulders are most influenced by the external environment. The coldest and warmest month temperatures at a certain depth are characterized by a spindle shape. The increase of the latitude and roadbed height may aggravate the transverse thermal regime difference. In addition, the roadbed transverse thermal difference may induce the uneven roadbed deformation, hence, the roadbed stability and the ride comfort of track structure maybe threated. Therefore, the relevant monitoring and deformation mechanics studies should be further reinforced. © 2017 15th International Conference of the International Association for Computer Methods and Advances in Geomechanics

关键词： Deformation

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Construction of stability monitoring and evaluation system for high-speed railway roadbed in cold regions 8

Construction of stability monitoring and evaluation system f...

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8th International Conference on Structural health monitoring of Intelligent Infrastructure, SHMII 2017

作者： Zhang, Yuzhi Sun, Baochen Zhao, Weigang Wen, An The Key Laboratory for Health Monitoring and Control of Large Structures in Hebei Province Shijiazhuang Tiedao University Shijiazhuang Hebei050043 China

ISBN: (纸本)9781925553055

Along with the development of economy, the high-graded transportation line project are extending towards the cold regions gradually. The high-speed railway (HSR) in cold regions requires extreme high stability, thus the rigorous enigineering demands challenge the roadbed stability severely. The construction of the automatic monitoring and evaluation system of the HSR roadbed in cold regions, to master the safety conditions in real time, will guarantee the safe operation of high-speed train strongly. Through the characteristics analysis of the HSR roadbed in cold regions, the monitoring indices, static deformation combined with dynamic responses, are determined. The layout plan of monitoring points, which integrates the transverse discontinuity with horizontal continuity, is put forward. On the basis of conquering the continous high-precision collection sensors and technology suitable for the severe environment in cold regions, the automatic continous monitoring system of the HSR roadbed is developed, and the evaluation method of roadbed stability based on the on-site data information mining and numerical model is built. The monitoring system and stability method have realized the continous monitoring and stability evaluation of the Harbin-Dalian HSR under the water-heat-load combined action. This will be conductive to provide the scientific support for the stability change mechanism, the operation and maintenance of the HSR roadbed in cold regions. © 2017 International Society for Structural health monitoring of Intelligent Infrastrucure. All rights reserved.

关键词： Railroads

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Effects of the reattachment on dry galloping in the critical Reynolds number range 9

Effects of the reattachment on dry galloping in the critical...

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9th Asia Pacific Conference on Wind Engineering, APCWE 2017

作者： Ma, Wenyong Liu, Qingkuan Liu, Xiaobing Key Laboratory for Health Monitoring and Control of Large Structure Shijiazhuang Tiedao University Hebei province China Department of Wind Science and Engineering Shijiazhuang Tiedao University Shijiazhuang City Hebei Province China

large amplitude vibrations of circular cylinders in the critical Reynolds number range are reproduced in wind tunnels. Displacements and wind pressure for the cylinders are measured synchronously to reveal the characteristics of aerodynamic force for the vibrating cylinders in a Reynolds number range where flow re-attaches on the rear of the cylinder. Effects of these reattachments on the aerodynamic forces and the vibrations are discussed. The results show that the reattachment can produce unsteady aerodynamic force and excite large amplitude vibration when it forms unstable separation bubble at the early critical Reynolds number range. Once it develops stable separation bubble, the reattachment mitigates the vibrations by creating strong negative aerodynamic damping. © 9th Asia Pacific Conference on Wind Engineering, APCWE 2017. All Rights Reserved.

关键词： Circular cylinders

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Effective concrete surface crack detection based on extreme learning machine 8

Effective concrete surface crack detection based on extreme ...

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8th International Conference on Structural health monitoring of Intelligent Infrastructure, SHMII 2017

作者： Wang, Baoxian Zhao, Weigang Zhang, Hao Wang, Xinmin Zhang, Guangyuan Structural Health Monitoring and Control Institute Shijiazhuang Tiedao University Shijiazhuang050043 China Key Laboratory for Health Monitoring and Control of Large Structures Shijiazhuang050043 China Collaborative Innovation Center of Large Infrastructure Disaster Prevention and Reduction of Hebei Province China

ISBN: (纸本)9781925553055

Concrete surface crack detection has been an important field for the safety of civil engineering structure. However, under the background of high-density data acquiring demand, the existing crack detecting methods could not obtain the favorable efficiency and capability. In this work, we present a novel concrete surface crack detector for efficiently dealing with the massive crack images. Specifically, discrete cosine transformation is firstly utilized to extract the frequency domain characteristics of concrete surface images. Then, with the calculated image frequency features, an emergent learning technique (i.e., Extreme Learning Machine) is exploited to find the optimal separate hyper-plane between the crack object and backgrounds. Experiments on the crack images from the railway ballast-less track slab validate the effectiveness of the proposed method. © 2017 International Society for Structural health monitoring of Intelligent Infrastrucure. All rights reserved.

关键词： Frequency domain analysis

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Multi-block SSD based on small object detection for UAV railway scene surveillance

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Chinese Journal of Aeronautics 2020年第6期33卷 1747-1755页

作者： Yundong LI Han DONG Hongguang LI Xueyan ZHANG Baochang ZHANG Zhifeng XIAO North China University of Technology Beijing 100144China Key Laboratory of Large Structure Health Monitoring and Control Shijiazhuang 050043China Unmanned System Research Institute Beihang UniversityBeijing 100083China Guangdong Provincial Key Laboratory of Computer Vision and Virtual Reality Technology Shenzhen Institutes of Advanced TechnologyChinese Academy of SciencesShenzhen 518055China School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100083China State Key Laboratory of Information Engineering in Surveying Wuhan UniversityWuhan 430079China

A method of multi-block Single Shot Multi Box Detector(SSD)based on small object detection is proposed to the railway scene of unmanned aerial vehicle *** address the limitation of small object detection,a multi-block SSD mechanism,which consists of three steps,is ***,the original input images are segmented into several overlapped ***,each patch is separately fed into an SSD to detect the ***,the patches are merged together through two *** the first stage,the truncated object of the sub-layer detection result is *** the second stage,a sub-layer suppression and filtering algorithm applying the concept of non-maximum suppression is utilized to remove the overlapped boxes of *** boxes that are not detected in the main-layer are *** addition,no sufficient labeled training samples of railway circumstance are available,thereby hindering the deployment of SSD.A two-stage training strategy leveraging to transfer learning is adopted to solve this *** deep learning model is preliminarily trained using labeled data of numerous auxiliaries,and then it is refined using only a few samples of railway scene.A railway spot in China,which is easily damaged by landslides,is investigated as a case *** results show that the proposed multi-block SSD method produces an overall accuracy of 96.6%and obtains an improvement of up to 9.2%compared with the traditional SSD.

关键词： Deep learning Multi-block Single Shot MultiBox Detector(SSD) Objection detection Railway scene Unmanned aerial vehicle remote sensing

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Low-cost and miniature all-silica Fabry–Perot pressure sensor for intracranial pressure measurement

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Chinese Optics Letters 2014年第11期12卷 49-52页

作者：李玉婷张文涛王兆刚许红彬韩晶李芳 Optoelectronics System Laboratory Institute of SemiconductorsChinese Academy of Sciences Key Laboratory of Structure Health Monitoring and Control of Hebei Province Shijiazhuang Tiedao University

The monitoring of increased intracranial pressure（ICP） is necessary in the diagnosis and treatment of patients with neurological disease because it can provide an insight into the mechanism of the head injury. In this letter, we develop a novel miniature Fabry–Perot（F-P） sensor for ICP measurement. The proposed sensor is fabricated by using a commercially available fusion splicer and a fiber cleaver, by which many difficult art problems involved in fabrication are solved and the online monitoring of the F-P cavity is actualized. The sensor exhibits a linear response to the applied pressure over the range of 0–25 k Pa（ample for ICP measurement）, with a sensitivity of 10.18 nm/k Pa, a resolution of 0.1 k Pa, and a reduced thermal sensitivity of 0.068 nm/°C, which shows it can meet the requirements of ICP measurement.

关键词： Low-cost and miniature all-silica Fabry Perot pressure sensor for intracranial pressure measurement ICP length

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Analysis on GPR echo signal enhancement algorithm based on subspace sparsity deconvolution

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Journal of Engineering Science and Technology Review 2016年第6期9卷 43-51页

作者： Yong, Yang Yanliang, Du Weigang, Zhao Baoxian, Wang Hao, Zhao School of Mechanical Electronic and Control Engineering Beijing Jiaotong University Beijing100044 China The Key Laboratory for Health Monitoring and Control of Large Structures in Hebei Province Shijiazhuang Tiedao University Shijiazhuang050043 China Department of Urban and Civil Engineering Ibaraki University Hitachi316-8511 Japan

Strong reflection interference of rebar is the main barrier against ground-penetrating radar (GPR) detection of internal diseases in reinforced concrete structure. Deconvolution can strengthen GPR echo data through acquiring structural layer data. However, existing deconvolution echo signal processing algorithms cannot be applied to process the GPR echo data because of the hypothesis that the wavelet is in the minimum phase system, which is inconsistent with the attenuation of GPR wavelet during two-way travel time. To resolve this problem, a new subspace sparsity deconvolution algorithm was proposed in this paper to enhance the echo signal of rebar lower diseases. A wavelet signal attenuation model of layered structure was firstly established to analyse the influencing factors of disease echo signal attenuation under different conditions. On this basis, the sparsity deconvolution algorithm based on wavelet iteration was placed to enhance GPR echo signal quickly by using the constraint condition of subspace errors. The processing of GPR forward simulation data also reveals that the proposed algorithm can inhibit noises effectively and acquire layer information from the concrete structure when the local signal-to-noise ratio is larger than -19.7dB. The proposed algorithm is clearly superior to the existing automatic gain control algorithm with respect to the echo enhancement effect of GPR. Results show that this method overcomes the minimum phase restriction of deconvolution and it is of great significance to detect and recognize inter-layer diseases of high-speed railway ballastless tracks. © 2016 Eastern Macedonia and Thrace Institute of Technology. All rights reserved.

关键词： Concrete construction

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