检索结果-内蒙古大学图书馆

numerical modeling of an umbrella arch as a pre-support system in difficult geological conditions: a case study

BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT 2016年第1期75卷 211-221页

作者： Elyasi, Ayub Bagherzadeh, Parisa Javadi, Mohammad Moradi, Taher Moharrami, Javad Parnian, Saeid Amrac, Mohsen Tarbiat Modares Univ Dept Min Engn Tehran Iran Tarbiat Modares Univ Dept Min Engn Fac Engn Tehran Iran Shadid Bahonar Univ Kerman Dept Min Engn Kerman Iran Consultant Engn Inst Iman Sazan Tehran Iran Univ Tehran Dept Min Engn Tehran Iran

In order to prevent the collapse of ceilings and walls of large tunnels, especially in difficult geological conditions, either a sequential excavation method (SEM) or ground reinforcing method, or a combination of both, can be utilized. The first part of the adit tunnel in northwestern Iran is being drilled in alluvium material with very weak geotechnical parameters. Despite applying an SEM in constructing this tunnel, analyzing the numerical modeling done using FLAC3D, as well as observations during drilling, indicate tunnel instability. To increase operational safety and to prevent collapse, a pre-support system was designed and implemented. The results of the numerical modeling accompanied by monitoring during operation, as well as the results of instrumentation, indicate the efficacy of this method for preventing collapse in alluvium material along the tunnel route. modeling the behavior of the umbrella arch shows that the location of the maximum compressive force will change with a change in the tunnel arc location. Moreover, displacement, force and moment exerted on the pipes will change during drilling steps according to a certain pattern.

关键词： SEM Alluvium material numerical modeling Pre-support system Monitoring Instrumentation

来源：评论

学校读者我要写书评

暂无评论

numerical modeling of miniature cyclone

引用

POWDER TECHNOLOGY 2017年 320卷 325-339页

作者： Sun, Ximing Zhang, Zhenzhong Chen, Da-Ren Tsinghua Univ Inst Nucl & New Energy Technol Beijing 100084 Peoples R China Tsinghua Univ Inst Nucl & New Energy Technol Collaborat Innovat Ctr Adv Nucl Energy Technol Key Lab Adv Reactor Engn & SafetyMinist Educ Beijing 100084 Peoples R China Virginia Commonwealth Univ Dept Mech & Nucl Engn Particle Lab 401 West Main St Richmond VA 23284 USA

In this work, fluid flow with particle motion in a miniature cyclone is simulated using a Eulerian-Lagrangian approach. The RNG k-epsilon, linear pressure-strain RSM, and low-Re stress-omega RSM models are investigated to describe air flow. Moreover, the discrete phase model (DPM) is applied to track particle motion. numerical prediction results are compared with experimental data. The three computational fluid dynamics models are proven suitable to the cyclone body alone without inlet contraction and outlet expansion. However, only the former two models are suitable for full cyclone prediction;they present a typical swirling flow coupled with an incoming jet flow because of their low-Re corrections, thereby yielding a low turbulent viscosity in the impinging region near the wall. Therefore, the DPM with the boundary condition of trap on inlet contraction section and cyclone bottom can track particle motion in a miniature cyclone. (C) 2017 Elsevier B.V. All rights reserved.

关键词： Miniature cyclone numerical modeling Eulerian-Lagrangian approach Pressure drop Penetration curve

来源：评论

学校读者我要写书评

暂无评论

numerical modeling of Photothermal Experiments on Layered Samples with Mirage-Effect Signal Detection

引用

INTERNATIONAL JOURNAL OF THERMOPHYSICS 2017年第6期38卷 1-12页

作者： Bodzenta, Jerzy Kazmierczak-Balata, Anna Bukowski, Roman Nowak, Marian Solecka, Barbara Silesian Tech Univ Inst Phys Konarskiego 22B PL-44100 Gliwice Poland

modeling of the probe beam deflection caused by temperature gradients for layered sample was realized in COMSOL Multiphysics, which utilizes finite element method to analyze heat transport. The sample consisted of a 100-nm-thick layer on a 500-mu m-thick substrate. It was also assumed that the sample was illuminated with either a Gaussian or a flat top beam of harmonically modulated intensity. To obtain the probe beam deflection signal, the normal and tangential components of the temperature gradient in the air above the sample were integrated over the probe beam path. The numerical model of the experiment gave insight into the various parameter dependencies, e.g., the thermal and optical properties of the substrate and the layer, and the geometry of the experiment. These insights are used in the analysis of experimental data and in the planning of future measurements.

关键词： Layered samples Mirage effect numerical modeling Photodeflection

来源：评论

学校读者我要写书评

暂无评论

numerical modeling of behavior of railway ballasted structure with geocell confinement

引用

GEOTEXTILES AND GEOMEMBRANES 2013年 36卷 33-43页

作者： Leshchinsky, Ben Ling, Hoe I. Oregon State Univ Dept Forest Engn Resources & Management Corvallis OR 97331 USA Columbia Univ Dept Civil Engn & Engn Mech New York NY 10027 USA

Railroad foundations are geotechnical structures that are highly dependent on quality ballast to dampen impact loading and railway vibration, facilitate easy construction, distribute stresses more evenly, reduce long-term settlements and provide a competent base under low confining pressures. However, there are various instances where the use of ballast alone may not be completely adequate or could be prohibitively expensive, i.e. costly transport of select materials, weak subgrade, etc. One possible method of managing these issues is the use of geosynthetics, primarily reinforcements that utilize a confining mechanism to enhance the strength of a soil by utilizing its own internal friction: a mechanism where geocell is applicable. Based on prior large-scale laboratory tests of ballast embankments with geocell confinement and relevant numerical modeling, an acceptable material model was validated for a parametric study using finite element analysis. The purpose of the parametric study is to investigate the effects of geocell confinement on ballasted embankments when encountering a soft subgrade, weaker ballast, or varying reinforcement stiffnesses. This analysis suggests that based on numerical modeling, geocell confinement can have a significant benefit when used on a wide range of subgrade stiffnesses, when using weaker ballast and that mechanically, most polymeric materials commonly used for geosynthetic reinforcements are adequate. The composite effect of the confined ballast selected as infill also demonstrates a "mattressing" effect, distributing stresses more uniformly to the subgrade, which can provide higher bearing capacities and possibly less settlement, all while preventing significant lateral spreading. In certain situations, the benefits provided by behavior of the geocell-ballast composite may be economical by allowing for use of weaker/inferior ballast, less embankment maintenance upon problem soils, improved bearing capacity and reduced foundation s

关键词： Railroad Ballast Geocell Confinement numerical modeling Finite element

来源：评论

学校读者我要写书评

暂无评论

numerical modeling of hypervelocity impacts

引用

INTERNATIONAL JOURNAL OF IMPACT ENGINEERING 2006年第1-12期33卷 244-253页

作者： Fortov, V. E. Kim, V. V. Lomonosov, I. V. Matveichev, A. V. Ostrik, A. V. Russian Acad Sci Inst Problems Chem Phys Chernogolovka 142432 Russia

This research presents a new "finite-size particle in cell" method developed for numerical modeling of processes at high energy density. It uses the Lagrangian-Eulerian representation of media which allows one to match contact and free surfaces and to calculate flows with strong deformations. Efficient models of thermodynamic properties, elastic-plastic deformation and fragmentation have been employed in the gas dynamic code adapted for parallel computations. 3D and 2D numerical modeling of plate penetration by impactors of different geometry has been done in a wide range of velocities. The influence of used materials properties models on numerical results has been investigated. (C) 2006 Elsevier Ltd. All rights reserved.

关键词： hypervelocity impact numerical modeling

来源：评论

学校读者我要写书评

暂无评论

numerical modeling of stress and strain associated with the bending of an oil pipeline by a migrating pingo in the permafrost region of the northern Tibetan Plateau

引用

ENGINEERING GEOLOGY 2008年第1-2期96卷 62-77页

作者： Wu, Zhenhan Barosh, Patrick J. Wang, Lianjie Hu, Daogong Wang, Wei PJ Barosh & Assoc Bristol RI 02809 USA Chinese Aca3demy Geol Sci Inst Geomech Beijing 100081 Peoples R China

Small seasonal pingos formed in Quaternary deposits along active fault zones in permafrost of the northern Tibetan Plateau exert destructive forces to oil pipelines, bridges, culverts and other engineering facilities along the Golmud-Lhasa railway and highway. The pingos are particularly hazardous as they change position, or migrate, nearly every year. Three-dimensional finite element modeling reveals the enormous force from exerted by a pingo at the 86th station of the highway. A good representation of the stress and strain fields resulting from an expansion of a pingo and bending of an oil pipeline at the station are calculated after due consideration of the interaction between permafrost, pingo and pipeline. This followed establishing an engineering-geologic model from the field data and determining the mechanical properties of the media from field and laboratory tests. The maximum, intermediate and the minimal principal compressive stresses are calculated as well as those for the plastic strain. Concentrations of principal stress and plastic strain occur beneath the pipeline bend and both the principal compressive stress and resulting plastic strain become very small away from the pingo. Also, the bottom of the pingo is dominated by minimal values of principal stress and strain and the potential bending of a buried pipe caused by an expansion of a pingo is indicated to decrease as depth of burial increases. The pingo growth at the 86th station resulted in the bending upward of a 20m section of a buried oil pipeline, but it did not break and spill oil. Analysis of the pipe within the bend found the maximum, intermediate, and minimal principal compressive stress ranges that leads to plastic strain within the bent pipe. Compressive stress and plastic strain concentrations form in the inner sides of inflexions in the pipe bend, and tensional stress and plastic strain concentrations form in their outer sides where stress exceeds the yield limit of the pipe, but many

关键词： migrating pingo numerical modeling stress plastic strain permafrost Tibetan Plateau hazard assessment Golmud-Lhasa Railway

来源：评论

学校读者我要写书评

暂无评论

numerical modeling of metal-dielectric metasurface as an element of microwave sensors for biomedical applications

引用

LOW TEMPERATURE PHYSICS 2024年第1期50卷 15-20页

作者： Kuznetsova, K. S. Pashynska, V. A. Eremenko, Z. E. NAS Ukraine O Ya Usykov Inst Radiophys & Elect UA-61085 Kharkiv Ukraine NAS Ukraine B Verkin Inst Low Temp Phys & Engn UA-61103 Kharkiv Ukraine Leibniz Inst Solid State & Mat Res D-01069 Dresden Germany

This paper reports the results of numerical modeling of wave reflection coefficient behavior of the metal-dielectric metasurface at microwaves that can be used for biomedical applications. The study includes optimization of the working parameters of the metasurface-based structure as a sensitive element of a microwave sensoring systems for determination of proteins concentration in different solutions. In the current research a unit with the geometry, which is similar to the geometry of one well of the standard 96-multiwell laboratory microplate, is used as a resonant metasurface unit cell and liquid-holding structure. Human serum albumin (HSA) is used as a protein specimen in our model study. The present numerical modeling is based on the results of our previous experimental measurements of complex permittivity values of HSA water solutions and its biochemical reaction mixtures using microwave dielectrometry method and the developed setup. The unit cell approach calculations are performed by COMSOL Multiphysics software. The optimization of working parameters of the metal-dielectric metasurface structure with tested solutions allow us to observe the resonance effects of the wave reflection coefficient in the microwave range. We can determine the HSA concentration changes in water solutions and enzymatic reaction mixtures by the resonance frequency shift of the wave reflection coefficient of the metal-dielectric metasurface. Developed metal-dielectric metasurface-based structure demonstrates prospects to be used as a sensitive element of microwave sensors for proteins concentration determination with biomedical purposes.

关键词： metal-dielectric metasurface microwave numerical modeling COMSOL multiwell plate Human serum albumin aqueous solution

来源：评论

学校读者我要写书评

暂无评论

numerical modeling of groundwater flow and nitrate transport using MODFLOW and MT3DMS in the Karaj alluvial aquifer, Iran

引用

ENVIRONMENTAL MONITORING AND ASSESSMENT 2023年第1期195卷 1-34页

作者： Shakeri, Reza Nassery, Hamid Reza Ebadi, Taghi Amirkabir Univ Technol Dept Civil & Environm Engn Tehran Iran Shahid Beheshti Univ Sch Earth Sci Dept Minerals & Groundwater Resources Tehran Iran

Nitrate is one of the most dangerous pollutants in groundwater, being regarded as a severe environmental hazard and a global-scale problem. The present study aims to analyze the groundwater flow and nitrate contamination in the Karaj unconfined aquifer, Central Iran. Simulation of the quantitative and qualitative status was performed using MODFLOW and MT3DMS. Sampling was done to model groundwater flow for eight seasonal time periods and nitrate pollution transport for four time periods (a total of 420 days), and calibration was carried out by trial-and-error method. Due to the predominance of advection term in the transport of nitrate pollution, the total variation diminishing method was used in transport modeling. The groundwater flow modeling showed a reservoir deficit of - 33 MCUM and 67 cm decrease in the water year 2016-2017 and 173 cm in the entire modeling period (2016-2018) in groundwater level. Also, the RMSE in the calibration and validation stages was obtained from 24.9 to 0.72 and 0.84, respectively. The nitrate contamination transport modeling indicated that there are three nitrate contamination concentration parts with more than safe concentration of nitrate (50 mg/l). The most pollution is in the urban areas in the east of the aquifer. The nitrate pollution is primarily anthropogenic due to industrial and especially domestic wastewater and then fertilizers used in agricultural activities. It can be predicted that with the full implementation of a municipal wastewater collection network, the nitrate pollution concentration in urban areas would reduce significantly to the range of 20 to 25 mg/l.

关键词： Groundwater MODFLOW numerical modeling Nitrate contamination MT3DMS Karaj alluvial aquifer

来源：评论

学校读者我要写书评

暂无评论

numerical modeling of Branching-Streamer Propagation in Ester-Based Insulating Oil Under Positive Lightning Impulse Voltage: Effects From Needle Curvature Radius

引用

IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 2023年第1期30卷 139-147页

作者： Li, Shi Wang, Feipeng Wang, Qiang Ouyang, Liangxuan Chen, Xiaoxiao Li, Jian Chongqing Univ State Key Lab Power Transmiss Equipment & Syst Sec Chongqing 400044 Peoples R China

Ester-based insulating oil provides the possibilities for controlling pollutant emissions and enhancing transformer safeties. A 2-D needle-plate electrode branching-streamer model has been established to numerically investigate the propagation characteristics of initial streamer branches and the effects from needle radius in ester-based insulating oil under lightning impulse (LI) voltage. The results indicate that by adding the source term that affects charge carrier density variation to the current continuity equation, the revised model could better capture the branching-streamer morphology in the experiment than the existing model. The accumulation of positive ions in the streamer branches promotes the electric field distortion, introducing the maximum electric field at the head of the streamer branches, which causes the appearance of the branching streamer due to the localized charge carrier surge (CCS). The electric field at the needle zone is affected by the curvature radius, and the smaller curvature radius enhances the electric field, allowing more space charge to be generated, which leads to easier distortion of the electric field at the head of the streamer branches and promotes forward propagation of the streamer branches. In addition, the smaller curvature radius contributes to the generation of the secondary streamer.

关键词： Oils Mathematical models Discharges (electric) Needles Impact ionization Electrodes Streaming media Dielectric fluids discharge ester-based insulating oil numerical modeling streamer branches

来源：评论

学校读者我要写书评

暂无评论

numerical modeling for Yield Pillar Design: A Case Study

引用

ROCK MECHANICS AND ROCK ENGINEERING 2015年第1期48卷 305-318页

作者： Li, Wenfeng Bai, Jianbiao Peng, Syd Wang, Xiangyu Xu, Ying China Univ Min & Technol Sch Mines Xuzhou Jiangsu Peoples R China W Virginia Univ Coll Engn & Mineral Resources Morgantown WV 26506 USA

Two single-entry gateroad systems employing a yield pillar for bump control in a Chinese coal mine were introduced. The overburden depth of the longwall panels was approximately 390 m. When the width/height (W/H) ratio of the yield pillar was 2.67, coal bumps in the tailgate occurred in front of the longwall retreating face. However, in another panel, the coal bump was eliminated because the W/H ratio was reduced to 1.67. Under this condition, instrumentation results indicated that the roof-to-floor and rib-to-rib convergences reached 1,050 and 790 mm, respectively, during longwall retreat. The numerical model was used to back-analyze the two cases of yield pillar application in the hope to find the principle for yield pillar design. In order to improve the reliability of the numerical model, the strain-hardening gob and strain-softening pillar materials were meticulously calibrated, and the coal/rock interface strength was determined by laboratory direct shear tests. The results of the validated model indicate that if the W/H ratio of the yield pillar equals 1.67, the peak vertical stress in the panel rib (37.7 MPa) is much larger than that in the yield pillar (21.1 MPa);however, the peak vertical stress in the panel rib (30.87 MPa) is smaller than that in the yield pillar (36 MPa) when the W/H ratio of yield pillar is 2.67. These findings may be helpful to the design of yield pillars for bump control.

关键词： Coal bumps Yield pillar design numerical modeling Gob and pillar model Coal/rock interface strength Stress analysis

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：