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  • Open Access

    ARTICLE

    Comparison of extracardiac conduit and lateral tunnel for functional single-ventricle patients: A meta-analysis

    Zhiyong Lin, Hanwei Ge, Jiyang Xue, Guowei Wu, Jie Du, Xingti Hu, Qifeng Zhao

    Congenital Heart Disease, Vol.12, No.6, pp. 711-720, 2017, DOI:10.1111/chd.12503

    Abstract Objective: This study aims to assess and compare the early and long-term effects of extracardiac conduit (EC) and lateral tunnel (LT) in patients with a functional single ventricle through metaanalysis.
    Design: A systematic search was performed in PubMed, Embase, Cochrane Library, CNKI, VIP, CBM, and WanFang databases for papers that were published until August 1, 2016. Cochrane systematic review method was used for paper screening and information retrieve, and RevMan 5.3 software was applied for the meta-analysis.
    Results: Data for 10 studies with a total of 3814 patients were retrieved. The advantages of EC comparing to LT include: lower 30… More >

  • Open Access

    ARTICLE

    Progressive loss of bone mass in children with Fontan circulation

    Simone Goa Diab1, Kristin Godang2, Lil‐Sofie Ording Müller3, Runar Almaas4, Charlotte de Lange3, Leif Brunvand1, Kari Margrethe Hansen1, Anne Grethe Myhre5, Gaute Døhlen1, Erik Thaulow1,6, Jens Bollerslev2,6, Thomas Möller1

    Congenital Heart Disease, Vol.14, No.6, pp. 996-1004, 2019, DOI:10.1111/chd.12848

    Abstract Objective: We investigated bone mineral density (BMD) at different ages after the Fontan completion, and we evaluated the relationship between BMD, vitamin D levels, and pertinent patient variables.
    Methods: A cross‐sectional sample of 64 patients was examined with dual‐energy X‐ray absorptiometry (DXA) scans to determine BMD. Of these patients, 24 were also examined with BoneXpert software to determine bone mass density (BMX), expressed as the bone health index (BHI). Blood samples from all patients were analyzed. Patients were divided into three different age groups; A: 4‐9 years old (n = 22), B: 10‐15 years old (n = 21), and C:… More >

  • Open Access

    ARTICLE

    Comparison between the Seismic Performance of Buried Pipes and Pipes in a Utility Tunnel

    Wei Liu1, 2, *, Qianxiang Wu2

    CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.2, pp. 661-690, 2020, DOI:10.32604/cmes.2020.07764

    Abstract A utility tunnel system consists of pipes and ancillary facilities. In this paper, a finite element model of a concrete utility tunnel with pipes inside is established. Several tunnel segments were built to simulate a real utility tunnel, while the pipe was fixed by springs on the brackets in the utility tunnel. Using the discrete soil spring element to simulate the soil-structure interaction, actual earthquake records were adopted as excitation to analyze the seismic responses of pipes in a utility tunnel. Moreover, the influences of different parameters, including soil type, earthquake records, and field apparent wave velocity on the seismic… More >

  • Open Access

    ARTICLE

    Laboratory Model Tests and DEM Simulations of Unloading- Induced Tunnel Failure Mechanism

    Abierdi1, Yuzhou Xiang2, Haiyi Zhong2, Xin Gu2, Hanlong Liu2, 3, Wengang Zhang2, 3, *

    CMC-Computers, Materials & Continua, Vol.63, No.2, pp. 825-844, 2020, DOI:10.32604/cmc.2020.07946

    Abstract Tunnel excavation is a complicated loading-unloading-reloading process characterized by decreased radial stresses and increased axial stresses. An approach that considers only loading, is generally used in tunnel model testing. However, this approach is incapable of characterizing the unloading effects induced by excavation on surrounding rocks and hence presents radial and tangential stress paths during the failure process that are different from the actual stress state of tunnels. This paper carried out a comparative analysis using laboratory model testing and particle flow code (PFC2D)-based numerical simulation, and shed light upon the crack propagation process and, microscopic stress and force chain variations… More >

  • Open Access

    ARTICLE

    An Investigation into the Effects of the Reynolds Number on High-Speed Trains Using a Low Temperature Wind Tunnel Test Facility

    Yundong Han1, Dawei Chen1, Shaoqing Liu1, Gang Xu2

    FDMP-Fluid Dynamics & Materials Processing, Vol.16, No.1, pp. 1-19, 2020, DOI:10.32604/fdmp.2020.06525

    Abstract A series of tests have been conducted using a Cryogenic Wind Tunnel to study the effect of Reynolds number (Re) on the aerodynamic force and surface pressure experienced by a high speed train. The test Reynolds number has been varied from 1 million to 10 million, which is the highest Reynolds number a wind tunnel has ever achieved for a train test. According to our results, the drag coefficient of the leading car decreases with higher Reynolds number for yaw angles up to 30º. The drag force coefficient drops about 0.06 when Re is raised from 1 million to 10… More >

  • Open Access

    ARTICLE

    Elastoplastic Analysis of Circular Tunnel in Saturated Ground Under Different Load Conditions

    Panpan Zhai1, 2, Ping Xu1, 2, *

    CMC-Computers, Materials & Continua, Vol.62, No.1, pp. 179-197, 2020, DOI:10.32604/cmc.2020.06474

    Abstract When a tunnel is excavated below the groundwater table, groundwater flows in through the excavated wall of the tunnel and seepage forces act on it. These forces significantly affect the ground reaction curve, which is defined as the relationship between the internal pressure and radial displacement of the tunnel wall. This study investigates analytical solutions for seepage forces acting on the lining of a circular tunnel under steady-state groundwater flow. Considering the tunnel’s construction or service period and boundary conditions, the direction of maximum principal stress changes, and the input stress of the Mohr-Coulomb criterion varies. The stress distribution and… More >

  • Open Access

    ARTICLE

    A Study of the Suitable Measurement Location and Metrics for Assessing the Vibration Source Strength Based on the Field-Testing Data of Nanchang Underground Railway

    Ling Zhang1, 2, Xiaoyan Lei1, Jian Jiang2, Qingsong Feng1

    Sound & Vibration, Vol.52, No.5, pp. 22-27, 2018, DOI:10.32604/sv.2018.04058

    Abstract Underground railway vibration source strength is one of the key values used for environmental impact assessment and the evaluation of mitigation measure’s performance. However, currently there is no international standard of measuring the underground railway vibration source strength for such purposes. The available local standards and industrial guidelines do not agree on measurement locations as well as the metrics for presenting the source strength. This has caused many confusions. This paper aims to study the suitable measurement location and metrics using the data from a large scale field-testing carried out at the Nanchang underground railway (Metro Line 1, China) in… More >

  • Open Access

    ARTICLE

    Dynamic Pressures on Tunnel Roofs due to Vehicle Passages

    James D. Barnes1, Ethan R. Brush1, Mark S. Newmark1, Eric E. Ungar1, *

    Sound & Vibration, Vol.52, No.4, pp. 6-8, 2018, DOI:10.32604/sv.2018.03737

    Abstract Pressure and proximity measurements made in a tunnel indicate that a typical vehicle passage produced on the tunnel roof an initial pressure increase of small magnitude, followed by a sharp and more substantial drop in pressure below atmospheric. The magnitude of the pressure drop was found to increase with smaller clearances between the vehicle top and the tunnel roof, consistent with the Bernoulli relation and the vehicle speed. The dynamic pressures potentially may have significant effects on the vibration and noise environments on the lower floors of “air rights construction” buildings that span highways. More >

  • Open Access

    ABSTRACT

    Face stability of shallow shield tunnels in dry sandy ground: model tests, discrete element method simulations and theoretical model

    Renpeng Chen, Linggang kong, Lvjun Tang, Yunmin Chen

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.20, No.4, pp. 99-100, 2011, DOI:10.3970/icces.2011.020.099

    Abstract Face stability is critical in the underground tunneling. In this report, large-scale model tests on the face stability of shallow tunnels for various cover depths (C/D = 0.5, 1, and 2) in dry sandy ground were firstly introduced. Then, a series of three-dimensional DEM models were built to simulated the process of tunnel face failure. The results of the model tests and DEM simulations reveal that a chimney like failure zone appears during the tunnel face failure. It was founded that with the increase of the horizontal displacement of the tunnel face, the support pressure decreases to the limit support… More >

  • Open Access

    ABSTRACT

    A Three-Dimensional Shield Tunnel Model Based on Generalized-FEM

    Lin Yifeng, Zhu Hehua, Cai Yongcang

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.20, No.2, pp. 51-52, 2011, DOI:10.3970/icces.2011.020.051

    Abstract Shield tunnel linings compose of segments , bolts, liners, et.al., which are quite different in geometry and mechanics. Traditional beam-spring joint model and shell-spring joint model is hard to simulate accurately the detailed characteristic. Classical three-dimensional FEM may cause serious mesh-generation difficulty and expensive calculation cost. Based on generalized finite element method and characteristics of shield tunnel, a three-dimensional shield tunnel structure model is established. In the proposed model a sixteen-node solid-shell generalized FE is devised and employed to simulate segments. Joints between segments or rings are modeled with a surface to surface contact generalized FE which comprise hidden-bolts and… More >

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