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Time reversal method for guided wave inspection in pipes

DENG Fei, WU Bin, HE Cunfu

《机械工程前沿（英文）》 2008年第3卷第3期页码 251-260 doi: 10.1007/s11465-008-0050-1

摘要： The application of the time reversal method in pipe-like structures based on finite element method (FEM) is investigated. A steel pipe model measuring 70 mm × 3.5 mm is used to analyze the reflection coefficient of the (0,2) mode with the time reversal process. Simulation results show that the time reversal array method is beneficial to the improvement of the signal-to-noise ratio of a guided wave inspection system. As the intercepting window is widened, more energy is included in re-emitted signals, which leads to a large reflection coefficient of the (0,2) mode. In parallel, a circumferential locating method based on the time reversal method is described. The time reversal process used for guided wave inspection leads to the temporal and spatial focusing. When the time reversal signals are re-emitted, the angular profile obtained at the axial location of the defect can be used to determine the circumferential location of the defect. Except for a pipe with one defect, the circumferential locating method has been verified on another pipe model with two defects. Meanwhile, the elements number of the time reversal array has been discussed for enhancing the discrimination of the defect circumferential location.

关键词： reversal process beneficial circumferential location energy number

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Analytical algorithms of compressive bending capacity of bolted circumferential joint in metro shield

《结构与土木工程前沿（英文）》页码 901-914 doi: 10.1007/s11709-023-0915-8

摘要： The integrity and bearing capacity of segment joints in shield tunnels are associated closely with the mechanical properties of the joints. This study focuses on the mechanical characteristics and mechanism of a bolted circumferential joint during the entire bearing process. Simplified analytical algorithms for four stress stages are established to describe the bearing behaviors of the joint under a compressive bending load. A height adjustment coefficient, α, for the outer concrete compression zone is introduced into a simplified analytical model. Factors affecting α are determined, and the degree of influence of these factors is investigated via orthogonal numerical simulations. The numerical results show that α can be specified as approximately 0.2 for most metro shield tunnels in China. Subsequently, a case study is performed to verify the rationality of the simplified theoretical analysis for the segment joint via numerical simulations and experiments. Using the proposed simplified analytical algorithms, a parametric investigation is conducted to discuss the factors affecting the ultimate compressive bending capacity of the joint. The method for optimizing the joint flexural stiffness is clarified. The results of this study can provide a theoretical basis for optimizing the design and prediciting the damage of bolted segment joints in shield tunnels.

关键词： shield tunnel segment joint joint structural model failure mechanism

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Ductile extension of 3-D external circumferential cracks in pipe structures

Wuchao YANG, Xudong QIAN

《结构与土木工程前沿（英文）》 2011年第5卷第3期页码 294-303 doi: 10.1007/s11709-011-0115-9

摘要： This study investigates the ductile fracture resistance of 3-D external circumferential cracks in the wall of a steel pipe under remote tension, using a damage-mechanism model originally proposed by Gurson and Tvergaard. The ductile crack extension utilizes an element extinction technique implemented in the computational cell framework. The key parameter for the computational cell method, i.e., the initial porosity ratio , is calibrated using both the fracture resistance and the load-deformation responses obtained from fracture tests of multiple single-edge bend [SE(B)] specimens made of high-strength steel, HY80, which has a yield strength of 630 MPa. The fracture resistance along the 3-D semi-elliptical crack front is computed from the calibrated cell model. Based on the similarity concept in the near-tip stress-strain fields, this study demonstrates that an equivalent 2-D axi-symmetric model provides conservative estimations of the fracture resistance for 3-D circumferential cracks in pipes.

关键词： ductile fracture computational cell method G-T model J-R curve

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On the potential of iPhone significant location data to characterize individual mobility for air pollution

《环境科学与工程前沿（英文）》 2022年第16卷第5期 doi: 10.1007/s11783-022-1542-7

摘要：

● We evaluated the accuracy of iPhone data in capturing time-activity patterns.

关键词： Air pollution exposure Human mobility iPhone Significant Location Smartphone data

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Space-time evolution rules study on acoustic emission location in rock under cyclic loading

Jiang XU, Shuchun LI, Yunqi TAO, Yongdong JIANG, Xiaojun TANG,

《结构与土木工程前沿（英文）》 2009年第3卷第4期页码 422-427 doi: 10.1007/s11709-009-0056-8

摘要： An acoustic emission (AE) location experiment was performed on sandstone using an advanced AE test system. The space-time evolution rule regarding damage was analyzed under cyclic loading as well as AE. The results show that AE on static loading process is consistent with the damage evolution rule of compression and the elastic-plastic deformation phase; at the beginning of cyclic loading with low duration time and energy, AE events came from a small crack. The location result showed that most events occurred in the core zone forming at the static loading process, and the location points changed slowly. AE energy changed little during the metaphase of cyclic process. There was a modest increase of location points in every cycle. The tendency of steady development could be predicted from the AE location events. At the end of each cyclic loading, the quantity of AE events and energy increased quite rapidly, reaching a maximum at the last cycle. AE events had high energy and duration time. Location events changed quite rapidly and assembled and linked continuously in the core zone. At the same time, they expanded to the top of specimen. A macroscopic crack finally formed. In the postfailure process, some AE events still existed due to fracturing of gliding friction. Owing to the inner stress balance of rock even after loading stopped, minor AE events still occurred.

关键词： location result AE location consistent friction elastic-plastic deformation

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Research and application of visual location technology for solder paste printing based on machine vision

Luosi WEI, Zongxia JIAO

《机械工程前沿（英文）》 2009年第4卷第2期页码 184-191 doi: 10.1007/s11465-009-0034-9

摘要： A location system is very important for solder paste printing in the process of surface mount technology (SMT). Using machine vision technology to complete the location mission is new and very efficient. This paper presents an integrated visual location system for solder paste printing based on machine vision. The working principle of solder paste printing is introduced and then the design and implementation of the visual location system are described. In the system, two key techniques are completed by secondary development based on VisionPro. One is accurate image location solved by the pattern-based location algorithms of PatMax. The other one is camera calibration that is achieved by image warping technology through the checkerboard plate. Moreover, the system can provide good performances such as high image locating accuracy with 1/40 sub-pixels, high anti-jamming, and high-speed location of objects whose appearance is rotated, scaled, and/or stretched.

关键词： machine vision visual location solder paste printing VisionPro

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Network-based optimization techniques for wind farm location decisions

Jorge Ignacio CISNEROS-SALDANA, Seyedmohammadhossein HOSSEINIAN, Sergiy BUTENKO

《工程管理前沿（英文）》 2018年第5卷第4期页码 533-540 doi: 10.15302/J-FEM-2018025

摘要：

This study aims to find appropriate locations for wind farms that can maximize the overall energy output while controlling the effects of wind speed variability. High wind speeds are required to obtain the maximum possible power output of a wind farm. However, balancing the wind energy supplies over time by selecting diverse locations is necessary. These issues are addressed using network-based models. Hence, actual wind speed data are utilized to demonstrate the advantages of the proposed approach.

关键词： wind energy wind farm location network analysis optimization clique s-plex

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Home location inference from sparse and noisy data: models and applications

Tian-ran HU,Jie-bo LUO,Henry KAUTZ,Adam SADILEK

《信息与电子工程前沿（英文）》 2016年第17卷第5期页码 389-402 doi: 10.1631/FITEE.1500385

摘要： Accurate home location is increasingly important for urban computing. Existing methods either rely on continuous (and expensive) Global Positioning System (GPS) data or suffer from poor accuracy. In particular, the sparse and noisy nature of social media data poses serious challenges in pinpointing where people live at scale. We revisit this research topic and infer home location within 100 m×100 m squares at 70% accuracy for 76% and 71% of active users in New York City and the Bay Area, respectively. To the best of our knowledge, this is the first time home location has been detected at such a fine granularity using sparse and noisy data. Since people spend a large portion of their time at home, our model enables novel applications. As an example, we focus on modeling people’s health at scale by linking their home locations with publicly available statistics, such as education disparity. Results in multiple geographic regions demonstrate both the effectiveness and added value of our home localization method and reveal insights that eluded earlier studies. In addition, we are able to discover the real buzz in the communities where people live.

关键词： Home location Mobility patterns Healthcare

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Leakage location system for oil pipeline on basis of stress wave detection

WANG Bangfeng, CHEN Renwen

《机械工程前沿（英文）》 2008年第3卷第3期页码 307-312 doi: 10.1007/s11465-008-0047-9

摘要： An online monitoring system was developed for rapidly determining the exact location of the holing position in an oil pipeline by monitoring and analyzing the characteristics of the strain wave caused by the hole. The system has a master-slaver computer structure based on a remote wireless network. The master system takes charge of managing and controlling the whole system, identifying the holing stress wave, and calculating the holing position. The slaver system is responsible for sampling the strain wave signal from the pipeline. The characteristics of the strain wave signal are extracted by a Hilbert-Huang transform based on a signal processing approach. The exact holing position can be obtained by a time delay locating method with stress wave characteristics. The experimental results of the in-service pipeline show that the average locating error of the system is less than 10 m, the accuracy ratio for the holing alarm is more than 90%, and the time that the system takes to respond to the leakage is less than 10 s.

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单站无源定位可观测性评述

邓新蒲

《中国工程科学》 2007年第9卷第11期页码 54-62

摘要：

可观测性分析是单观测器无源定位首先要研究的问题，只有当目标状态 (位置、速度等)是完全可观测的，定位和跟踪问题才能有可靠的、唯一的解。从几何方法、代数方程方法、线性系统方法3方面来阐述单站测角无源定位的状态可观性问题，讨论测频单站无源定位问题的可观测性和定量的可观测性，并对近年来这一领域的相关文献的分析方法和结论进行评述。

关键词：无源定位 TMA 可观测性

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Erratum to: On the potential of iPhone significant location data to characterize individual mobility

《环境科学与工程前沿（英文）》 2022年第16卷第9期 doi: 10.1007/s11783-022-1556-1

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On the location of the secondary instantaneous poles in two-degree-of-freedom spherical mechanisms

Soheil ZARKANDI

《机械工程前沿（英文）》 2014年第9卷第1期页码 34-40 doi: 10.1007/s11465-014-0290-1

摘要：

As the instant centers in planar mechanisms, the instantaneous poles (or instant poles, in brief) can be used for kinematic analysis in spherical mechanisms. One of the mandatory steps in this analysis is the determination of the location of these poles. This paper presents a theorem showing analytically that the locus of an unknown secondary instant pole in two-degree-of-freedom (2-DOF) spherical mechanisms is a great circle (GC). The exact location of the pole on its GC is obtained based on the configuration of the mechanism and velocity ratio of the two inputs. Moreover, using the results of the theorem, a geometrical technique is presented to determine the GC of the pole.

关键词： spherical mechanisms instantaneous poles great circle angular velocity

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矿山微震震源定位研究进展与展望 Review

程久龙,宋广东,孙晓云,温来福,李飞

《工程（英文）》 2018年第4卷第5期页码 653-660 doi: 10.1016/j.eng.2018.08.004

摘要：

震源定位是微震监测技术的核心要素，微震震源定位的准确性关系到微震技术的应用效果。针对矿山微震波场特征，分析了矿山微震定位的特点，指出了基于到时的经典定位方法用于矿山微震定位存在的不足。介绍了近几年来在矿山微震定位方面的研究进展，主要包括Geiger 方法与线性方法联合定位、联合微震事件定位、相对定位法优化、无需预先测速的定位方法、无需拾取初至到时的定位方法，分析各方法的优缺点和可行条件。分析了检波器布置、初至到时拾取、波速模型对微震震源定位的影响，提出了应对措施。解决上述问题的方法包括采用新型融合、组合优化已有的方法、创建新方法以实现高精度微震震源定位。提出了矿山微震精确定位的发展方向，即速度模型优化、逆时成像、被动时间反转镜法、相对干涉成像法等新方法的应用，有望大大提高矿山微震震源定位精度。同时，探讨了多方法多参数信息融合和深度学习在矿山微震定位中的应用前景。这些创新性的微震震源定位方法具有广阔的发展前景。

关键词：微震震源定位影响因素逆时成像研究进展发展前景

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Moving target detection in the cepstrum domain for passive coherent location (PCL) radar

Ji-chuan LI,Xiao-de LU,Hui ZHANG,Peng-cheng YANG,Yu LIU,Mao-sheng XIANG

《信息与电子工程前沿（英文）》 2015年第16卷第9期页码 785-795 doi: 10.1631/FITEE.1500036

摘要： A cepstrum moving target detection (CEPMTD) algorithm based on cepstrum techniques is proposed for passive coherent location (PCL) radar systems. The primary cepstrum techniques are of great success in recognizing the arrival times of static target echoes. To estimate the Doppler frequencies of moving targets, we divide the radar data into a large number of segments, and reformat these segments into a detection matrix. Applying the cepstrum and the Fourier transform to the fast and slow time dimensions respectively, we can obtain the range information and Doppler information of the moving targets. Based on the CEPMTD outlined above, an improved CEPMTD algorithm is proposed to improve the detection performance. Theoretical analyses show that only the target’s peak can be coherently added. The performance of the improved CEPMTD is initially validated by simulations, and then by experiments. The simulation results show that the detection performance of the improved CEPMTD algorithm is 13.3 dB better than that of the CEPMTD algorithm and 6.4 dB better than that of the classical detection algorithm based on the radar cross ambiguity function (CAF). The experiment results show that the detection performance of the improved CEPMTD algorithm is 1.63 dB better than that of the radar CAF.

关键词： Moving target detection Cepstrum techniques Cross ambiguity function (CAF) Passive coherent location (PCL) radar

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火灾中燃料失重速率与烟气向远距离处迁移关系的实验研究

冯文兴,杨立中,方廷勇,黄锐,范维澄

《中国工程科学》 2005年第7卷第1期页码 81-85

摘要：

通过不同燃料在模拟房间—走廊结构实验装置中的燃烧实验，较系统地揭示了不同材料燃烧时失重速率变化与远距离处烟气迁移速度和CO浓度的关系。实验得到了不同燃料燃烧时的失重速率曲线。研究发现，多数燃料的烟气传播速度与失重速率呈线性变化的关系，油料和布料的烟气传播速度对质量失重速率的变化非常敏感；某些燃料燃烧产生有毒成分的峰值迁移到远距离处需要较长的时间。

关键词：火灾失重速率远距离处迁移速度烟气毒性