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Numerical and experimental analyses of methane leakage in shield tunnel

《结构与土木工程前沿（英文）》页码 1011-1020 doi: 10.1007/s11709-023-0956-z

摘要： Tunnels constructed in gas-bearing strata are affected by the potential leakage of harmful gases, such as methane gas. Based on the basic principles of computational fluid dynamics, a numerical analysis was performed to simulate the ventilation and diffusion of harmful gases in a shield tunnel, and the effect of ventilation airflow speed on the diffusion of harmful gases was evaluated. As the airflow speed increased from 1.8 to 5.4 m/s, the methane emission was diluted, and the methane accumulation was only observed in the area near the methane leakage channels. The influence of increased ventilation airflow velocity was dominant for the ventilation modes with two and four fans. In addition, laboratory tests on methane leakage through segment joints were performed. The results show that the leakage process can be divided into “rapid leakage” and “slight leakage”, depending on the leakage pressure and the state of joint deformation. Based on the numerical and experimental analysis results, a relationship between the safety level and the joint deformation is established, which can be used as guidelines for maintaining utility tunnels.

关键词： shield tunnel harmful gas leakage numerical analysis laboratory test

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Experimental study of pollution effect on the behavior of high voltage insulators under alternative current

Hani BENGUESMIA, Nassima M’ZIOU, Ahmed BOUBAKEUR

《能源前沿（英文）》 2021年第15卷第1期页码 213-221 doi: 10.1007/s11708-017-0479-1

摘要： In this paper, the impact of the conductivity and the distribution of pollution on the behavior of the high voltage insulator cap and pin 1512L, artificially polluted is described. An experimental model in form of a disc is proposed. This experimental model reproduces the real model which is the 1512L insulator. Besides, a comparative study is presented. For this comparative study, different solutions are adopted to s`imulate the pollution (containing NaCl+ distilled water) that has different conductivities for a discontinuous distribution of the pollution on the insulator under an AC voltage. Furthermore, the influence of the pollution on the flashover voltage and the leakage current is studied. Finally, the behavior of real and experimental model of the insulator is investigated.

关键词： 1512L insulator circular model artificial pollution flashover leakage current discontinuous pollution high voltage

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Effects of leakage and friction on the miniaturization of a Wankel compressor

Yilin ZHANG, Wen WANG

《能源前沿（英文）》 2011年第5卷第1期页码 83-92 doi: 10.1007/s11708-010-0125-7

摘要： This paper presents a numerical simulation of the performance of a meso-scale Wankel compressor and discusses the factors affecting its miniaturization. The discussion is related to the effect of leakage and friction on the design limit (cooling capacity and dimension) of the meso Wankel compressor. In the simulation, the main leakage comes from the gaps between the rotor and the endplates as well as between the seal apex and the cylinder. The largest friction originates from the clearance among the end face of the eccentric shaft, the end faces of the rotor, and the endplates. The decreasing cooling capacity of the meso Wankel compressor increases the proportion of leakage to displacement and causes the coefficient of performance COP and the mechanical efficiency to decrease. The rational design cooling capacity limit for the meso-scale Wankel compressor is approximately 4 W.

关键词： meso-scale Wankel compressor leakage friction

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Cohesive zone model-based analyses of localized leakage of segmentally lined tunnels

《结构与土木工程前沿（英文）》 2023年第17卷第4期页码 503-521 doi: 10.1007/s11709-023-0927-4

摘要： This paper presents a novel approach for simulating the localized leakage behavior of segmentally lined tunnels based on a cohesive zone model. The proposed approach not only simulates localized leakage at the lining segment, but also captures the hydromechanically coupled seepage behavior at the segmental joints. It is first verified via a tunnel drainage experiment, which reveals its merits over the existing local hydraulic conductivity method. Subsequently, a parametric study is conducted to investigate the effects of the aperture size, stratum permeability, and spatial distribution of drainage holes on the leakage behavior, stratum seepage field, and leakage-induced mechanical response of the tunnel lining. The proposed approach yields more accurate results than the classical local hydraulic conductivity method. Moreover, it is both computationally efficient and stable. Localized leakage leads to reduced local ground pressure, which further induces outward deformation near the leakage point and slight inward deformation at its diametrically opposite side. A localized stress arch spanning across the leakage point is observed, which manifests as the rotation of the principal stresses in the adjacent area. The seepage field depends on both the number and location of the leakage zones. Pseudostatic seepage zones, in which the seepage rate is significantly lower than that of the adjacent area, appear when multiple seepage zones are considered. Finally, the importance of employing the hydromechanical coupled mechanism at the segment joints is highlighted by cases of shallowly buried tunnels subjected to surface loading and pressure tunnels while considering internal water pressure.

关键词： segmentally lined tunnel localized leakage cohesive element hydraulic behavior numerical modeling

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Long-term settlement behavior of ground around shield tunnel due to leakage of water in soft deposit

Huaina WU, Yeshuang XU, Shui-long SHEN, Jin-chun CHAI

《结构与土木工程前沿（英文）》 2011年第5卷第2期页码 194-198 doi: 10.1007/s11709-011-0105-y

摘要： The lining of shield tunnel is usually composed of segments, in which the joints, cracks, and the grouting holes (hereafter called lining deficit) exist. During the long-term running, soils and groundwater may leak from these kinds of lining deficit. The leaking of soil and groundwater causes the long-term ground loss around tunnel and thus results in the settlement of ground surface. This paper aims to analyze the impact of the leakage of groundwater through segments on the long-term settlement of ground surface. The adopted analytical method is based on the theory of groundwater seepage by using numerical simulation. The analyzed results show that settlement of ground surface increases gradually with the increase of the leaked volume of tunnel segments. When the leaked volume was unevenly distributed, differential settlement occurred locally. Comparative analysis by changing the leaked volume was conducted. The results reveal that there is a linear relationship between settlement and leaked volume when the leaked volume was controlled within the allowable limit.

关键词： lining deficit leakage of water shield tunnel settlement soft deposit

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A building unit decomposition model for energy leakage by infrared thermography image analysis

Yan SU, Fangjun HONG, Lianjie SHU

《能源前沿（英文）》 2020年第14卷第4期页码 901-921 doi: 10.1007/s11708-020-0679-y

摘要： A quantitative energy leakage model was developed based on the thermography image data measured for both external and internal building surfaces. The infrared thermography images of both surfaces of doors, windows, and walls of an office building in the Hengqin Campus of University of Macao were taken at various times in a day for four seasons. The transient heat ﬂux for sample units were obtained based on measurements of the seasonal transient local temperature differences and calculations of the effective thermal conductivity from the multiple-layer porous medium conduction model. Effects of construction unit types, orientations, and seasons were quantitatively investigated with unit transient orientation index factors. The corresponding electric energy consumption was calculated based on the air conditioning system coefficient of performance of heat pump and refrigerator cycles for different seasons. The model was validated by comparing to the electric meter records of energy consumption of the air conditioning system. The uncertainties of the predicted total building energy leakage are about 14.7%, 12.8%, 12.4%, and 15.8% for the four seasons, respectively. The differences between the predicted electric consumption and meter values are less than 13.4% and 5.4% for summer and winter, respectively. The typical daily thermal energy leakage value in winter is the highest among the four seasons. However, the daily electric energy consumption by the air conditioning system in summer and autumn is higher than that in winter. The present decomposition model for energy leakage is expected to provide a practical tool for quantitative analysis of energy leakage of buildings.

关键词： heat conductivity heat coefficient heat &fllig ux infrared thermography thermal image

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海洋CO2管道输送技术现状与展望

王子明,李清平,李姜辉,范振宁,张建

《中国工程科学》 doi: 10.15302/J-SSCAE-2023.06.017

摘要：

管道输送是经济高效的CO2运输方式，海洋CO2运输是离岸碳捕集、利用与封存（CCUS）产业链的关键环节和规模化开展离岸CCUS工程建设所需的核心技术。本文明晰了我国实施离岸CCUS的优势、典型海洋碳运输情境和海洋CO2运输方式，剖析了国内外海洋CO2管道输送的技术与工程概况；从CO2流体相态及流动安全，沿程腐蚀风险评估、监测及预警，CO2泄漏实时监测技术，高压CO2泄放及对环境的影响等方面梳理了海洋CO2管道输送工艺技术现状；从CO2管道材料断裂行为及止裂措施、高耐蚀及密封材料、碳钢管道长寿命运行的关键腐蚀控制技术、注采井筒的腐蚀风险评估等方面梳理了海洋CO2管道材料技术现状。研究认为，加快发展适应海洋CO2管道输送复杂工况的材料体系、全流程CO2管道的智慧管理与数字孪生技术、海底CO2管道全生命周期运行关键技术、在役海底管道改输评估与保障技术，采取加快推动我国近海碳封存CO2管网规划、拓展和深化跨行业 / 跨机构合作模式创新、系统建设海陆统筹的标准体系、引导专业化技术服务企业深度参与海底CO2管网建设等举措，促进我国海洋CO2管道输送体系高质量建设。

关键词： CO2管道；离岸CCUS；海底管道；管道腐蚀；管道断裂；泄漏监测

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Aggravation of membrane fouling and methane leakage by a three-phase separator in an external anaerobic

Chao Pang, Chunhua He, Zhenhu Hu, Shoujun Yuan, Wei Wang

《环境科学与工程前沿（英文）》 2019年第13卷第4期 doi: 10.1007/s11783-019-1131-6

摘要：

The existence of three-phase separator did not affect COD removal in the EAnCMBR.

The existence of three-phase separator aggravated methane leakage of EAnCMBR.

The existence of three-phase separator aggravated membrane fouling rate of EAnCMBR.

Start-up of EAnCMBR equipped three-phase separator was slightly delayed.

关键词： Anaerobic membrane bioreactor Three-phase separator Membrane fouling Methane leakage Sludge property

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在现场可编程门阵列中用于降低泄漏功率的动态电源门控 Research Article

Hadi JAHANIRAD

《信息与电子工程前沿（英文）》 2023年第24卷第4期页码 582-598 doi: 10.1631/FITEE.2200084

摘要：现场可编程门阵列（FPGA）器件由于其低设计成本和可重构性，在电子系统中得到广泛应用。在手持电子系统等电池受限的应用中，低功耗FGPA的需求很大。在现代集成电路技术中，泄漏功率几乎相当于动态功率，因此降低泄漏功率可以显著节省能耗。我们提出一种基于静态随机存取存储器（SRAM）的FPGA高效架构，其中每个模块定义了两种模式（活动模式和休眠模式）。在休眠模式下，模块消耗超低泄漏功率。当模块输出对新输入向量的评估时，模块模式由休眠模式动态改变为活动模式。在产生正确的输出后，该模块返回到休眠模式。所提电路设计在活动模式和休眠模式下都降低了泄漏功耗。通过在FPGA-SPICE软件上实现北卡罗来纳州微电子中心（MCNC）基准电路，将所提出的低泄漏FPGA体系结构与最先进的体系结构进行比较。仿真结果表明，休眠模式下泄漏功耗降低约95%。此外，与以往的最佳设计相比，总功耗（泄漏功耗+动态功耗）降低15%以上。平均面积开销（4.26%）小于其他电源门控设计。

关键词：现场可编程门阵列（FPGA）；泄漏功率；电源门控；晶体管级电路设计

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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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利用机器视觉技术对化工厂管道进行自动视觉泄漏检测与定位 Reiew

Mina Fahimipirehgalin, Emanuel Trunzer, Matthias Odenweller, Birgit Vogel-Heuser

《工程（英文）》 2021年第7卷第6期页码 758-776 doi: 10.1016/j.eng.2020.08.026

摘要：

在大型化工厂中，输送液体的管道的泄漏是一个重要的问题。管道的破损不仅会影响工厂的正常运行，同时也增加了维护成本。此外，还会使操作人员的生命安全受到威胁。因此，管道泄漏的检测与定位是维护和状态监测中的关键任务。近年来，大型工厂利用红外（IR）相机进行泄漏检测。红外相机可捕捉温度比周围环境温度高（或低）的液体泄漏。本文针对化工厂中的管道泄漏，提出了一种基于红外视频数据和机器视觉技术的检测与定位方法。由于所提出的方法是以视觉技术为基础，无需考虑泄漏液体的物理性质，因此其适用于任何类型的液体（水、油等）泄漏检测。在本方法中，首先对后续帧进行减影和分块处理，然后对每一分块进行主成分分析，提取特征；接着将分块内所有减影帧都转换为特征向量（作为块分类的依据），根据特征向量，采用k-最近邻算法将块分为正常（无泄漏）和异常（泄漏）两类；最后在各异常块上确定泄漏的位置。本文使用了两种不同格式的数据集（由红外相机拍摄的实验室工厂演示装置的视频图像组成）对上述方法进行评估。结果表明，本文提出的利用红外视频进行管道泄漏检测与定位的方法前景可观，具有较高的检测精度以及合理的检测时间。本文最后讨论了该方法在工厂进行实际推广的可能性及局限性。

关键词：泄漏检测与定位图像分析图像预处理主成分分析 k-最近邻分类

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Modeling and analysis of magnetic dipoles in weak magnetic field

WANG Zhaoxia, ZHANG Weimin, LIU Hongguang

《机械工程前沿（英文）》 2008年第3卷第2期页码 222-225 doi: 10.1007/s11465-008-0028-z

摘要： The magnetic leakage field distribution resulting from linear defects of a tube sample in the geomagnetic field is modeled according to the magnetic dipole theory. The formula to compute the normal component of the weak magnetic field is deduced based on the spatial distribution of the magnetic dipole. The shape and characteristics of the zero line (an important criterion for magnetic memory testing) of the normal field is analyzed under different longitudinal magnetizations. Results show that the characteristics of the zero line should be considered when the metal magnetic memory testing method is used to find and locate the defect.

关键词： geomagnetic theory important criterion magnetic leakage normal component

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Effect of current density on groundwater arsenite removal performance using air cathode electrocoagulation

《环境科学与工程前沿（英文）》 2021年第15卷第6期 doi: 10.1007/s11783-021-1399-1

摘要：

• With the same charge, current density had little effect on As(III) removal in ACEC.

关键词： Electrocoagulation Air cathode Arsenic Current density Energy consumption

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EGG PRODUCTION IN CHINA: CURRENT STATUS AND OUTLOOK

Ning YANG

《农业科学与工程前沿（英文）》 2021年第8卷第1期页码 25-34 doi: 10.15302/J-FASE-2020363

摘要： Eggs are one of the most nutritious and affordable animal products worldwide. From 1985, egg production in China has retained the leading place in the world. A total of 33 Mt of eggs were produced in 2019 representing ˃ 40% of the world total production. Egg production in China is characterized by diversity in several aspects, including layer breeds, products and production systems. New breeds and synthetic lines are developed to improve the genetic potentials of egg production and feed efficiency of layers. In the past, layer farms were run mostly by small households with 100 to 1000 layers per farm. Over the past decades, egg production in China has developed toward standardization and expansion of production systems, and many of these modern intensive farms raise millions of layers. Although the Chinese egg products maintain strong competitiveness over other animal products and imported egg products, the egg industry will grow at a slower pace compared to the past. Chinese consumers are more concerned about the quality and safety of eggs and egg products, as well as the environmental issues related to animal production, which presents challenges for the Chinese egg industry.

关键词： poultry farms China diversity egg production trends

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基于迭代算法的有源电力滤波器谐波电流实时检测新方法

李自成,孙玉坤

《中国工程科学》 2006年第8卷第1期页码 46-50

摘要：

目前，已经提出了多种有源电力滤波器谐波及无功电流检测方法，尽管这些方法各有特点，但都存在着难以克服的问题，如计算量大，实时性差，检测精度不高等。文章在负载电流分析的基础上，提出了一种基于迭代算法的有源电力滤波器谐波电流实时检测方法，该方法具有计算量非常小，实时性好，检测精度高等特点。理论分析与仿真研究证实了该方法的正确性。

关键词：有源电力滤波器谐波电流有功电流无功电流