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shrinkage of magnetosphere observed by TC-1 satellite during the high-speed solar wind stream

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Science China(Technological Sciences) 2008年第10期51卷 1695-1703页

作者： H. RME I. DANDOURAS C. M. CARR Centre d'Etude Spatiale des Rayonnements BP 4346 31028 Toulouse cedex 4 France The Blackett Laboratory Imperial College London SW7 2BZ UK

During the interval 06:14―07:30 UT on August 24, 2005, since the Earth’s magneto- pause was suddenly compressed by the persistent high-speed solar wind stream with the southward component of the interplanetary magnetic field (IMF), the magnetopause moved inward for about 3.1 RE. Meanwhile, TC-1 satellite shifted from northern plasma sheet to the northern lobe/mantle region, although it kept inward flying during the interval 06:00―07:30UT. The shift of TC-1 from the plasma sheet to the lobe/mantle is caused by the simultaneous inward displacements of the plasma sheet and near-Earth lobe/mantle region, and their inward movement velocity is larger than the inward motion velocity of TC-1. The joint inward dis-placements of the magnetopause, the lobe/mantle region and the plasma sheet indicate that the whole magnetosphere shrinks inward due to the magnetospheric compression by the high-speed solar wind stream, and the magnetospheric ions are attached to the magnetic field lines (i.e. ‘frozen’ in magnetic field) and move inward in the shrinking process of magnetosphere. The large shrinkage of magne-tosphere indicates that the near-Earth magnetotail compression caused by the strong solar wind dynamic pressure is much larger than its thickening caused by the southward component of the IMF, and the locations of magnetospheric regions with different plasmas vary remarkably with the variation of the solar wind dynamic pressure.

关键词： solar wind dynamic pressure shrinkage of magnetosphere storm sudden commencement substorm

shrinkage Reducing Measures for Engineering Cementitious Composites

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Journal of Wuhan University of Technology(Materials Science) 2008年第6期23卷 907-911页

作者：杨英姿 School of Civil Engineering Harbin Institute of Technology China Building Materials Academy

Inhibition measurement of shrinkage of engineering cementitious composites （ECC） was investigated due to typical ECC with higher free drying *** effects of expanded admixture （EA）,shrinkage reducing admixture （SRA）,coarse sand＋stone powder （CS＋SP） and superabsorbent polymer （SAP） on drying shrinkage and mechanical properties were *** experimental results show that ECC incorporating EA,SRA and coarse sand can retain around 60% of the typical ECC＇s free drying *** polymerl（SAP） can delay the development of free drying shrinkage of ECC at different ages,and the effect of SAP is not distinct like the actions of EA,superabsorbent polymer（SRA） and coarse ***,SAP may act as artificial flaw to form a more homogeneous defect system that increases the potential of saturated multiple cracking,hence the ductility of ECC will be improved greatly.

关键词： engineered cementitious composites (ECC) shrinkage SAP

shrinkage Behavior of High Performance Concrete at Different Elevated Temperatures under Different Sealing Conditions

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Journal of Wuhan University of Technology(Materials Science) 2006年第3期21卷 138-141页

作者：潘志华 NAKAMURA Hidemi WEE Tionghuan College of Materials Science & Engineering Nanjing University of TechnologyNanjing 210009China Research and Development Center Taiheiyo Cement CorporationChiba 285-8655Japan Department of Civil Engineering National University of SingaporeSingapore

The shrinkage behavior of high performance cement concrete made from Portland cement, ultra fine granulated blast furnace slag and pulverized fly ash with addition of superplasticizer at different temperatures from ambient temperature to 120 ℃ under different seuliug conditions was investigated by means of length change measurement on cylindrical concrete specimens along with curing age. Results show that drying shrinkage deformations of titled concrete specimens increased rapidly as the curing temperature rose. The development of dryiing shrinkage deformatian can be efficiently controlled with the aid of aluminum tape sealing as compared with the unsealed specimens, especially when the curing temperature is below 60℃ , although it will increase dramatically when the curing temperature is elevated to above 90%＂ . Polymer coating on concrete specimens showed a similar effect on the control of drying shrinkage as the sealing operation with aluminum tape.

关键词： high performance concrete shrinkage granulated blast-furnace slag fly ash elevated temperature sealing condition

Influence of curing conditions on the shrinkage behavior of three-dimensional printed concrete formwork

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Frontiers of Structural and Civil Engineering 2024年第8期18卷 1225-1236页

作者： M.BEKAERT K.van TITTELBOOM G.de SCHUTTER Magnel-Vandepitte Laboratory for structural Engineering and Building Materials Department of Structural Engineering and Building MaterialsFaculty of Engineering and ArchitectureGhent UniversityGhent 60 B-9052Belgium

The use of three-dimensional(3D)printed concrete as formwork is becoming more widely applied within the ***,the technology is still not optimized and there are many reports of preliminary cracking during the curing of cast *** is believed to result from differential shrinkage between the printed and cast *** cracks(in the printed concrete or at the interface between the infill and printed concrete)form a preferential path for aggressive substances and can reduce the durability of the combined concrete *** ensure the desired service life of the structure,it is important that the differential shrinkage between cast and printed concrete is *** study investigated the effect of curing conditions on the differential shrinkage behavior of 3D and cast *** influence of prewetting of the dry-cured 3D printed formwork was also *** the experimental program,a vibrated and self-compacting concrete were used as cast *** 3D printed formwork was produced and combined with cast concrete to simulate a concrete *** formwork was cured for 1,7,or 28 d exposed to the air(relative humidity:60%or 95%)or submerged in *** length change of the combined elements was observed over 56 d after concrete casting and throughout the thickness of the *** show that increasing the curing period in dry conditions of the printed concrete leads to an expansion of the formwork on the first day after *** expansion leads to a non-uniform strain evolution throughout the curing period of the combined *** concrete formwork stored in wet conditions does not expand after the casting process but tends to show a decreasing linear deformation within the whole elements.

关键词： 3D concrete printing formwork shrinkage curing

Effects of microfine aggregate in manufactured sand on bleeding and plastic shrinkage cracking of concrete

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Frontiers of Structural and Civil Engineering 2022年第11期16卷 1453-1473页

作者： Branavan ARULMOLY Chaminda KONTHESINGHA Anura NANAYAKKARA Department of Civil Engineering University of Sri JayewardenepuraMount Lavinia 10370Sri Lanka Department of Civil Engineering University of MoratuwaMoratuwa 10400Sri Lanka

Construction industries have started to utilize manufactured sand(MS)as an effective alternative for river sand in ***-grade parent rocks are crushed to obtain MS,which also produces a considerable amount of microfine aggregate(MFA).The higher percentage of MFA could lead to both positive and negative effects on the performance of cement-based *** research was done to examine the influence of varying MFA levels,specifically 0%,3%,6%,9%,and 12%(by weight)as the partial replacements of MS on bleeding and plastic shrinkage cracking of *** addition to the varying MFA levels,some concrete mixes also included fly ash(FA)and superplasticizer to investigate the effect of free-water content in the *** bleeding test data were taken as on-site measurements,while the cracks from the plastic shrinkage cracking test were evaluated using an image processing *** results concluded that the MFA replacements and the effective water-to-cement ratio have a significant effect on the selected concrete *** the increasing replacement levels,cumulative bleeding and crack initiation life gradually decreased,while a progressive increase was observed for crack width,crack length,and crack area.

关键词： manufactured sand fresh concrete microfines admixtures shrinkage cracking

Pre-reinforcement grout in fractured rock masses and numerical simulation for optimizing shrinkage stoping configuration

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Journal of Central South University 2017年第12期24卷 2924-2931页

作者： YU Shao-feng WU Ai-xiang WANG Yi-ming LI Tao School of Civil and Resource Engineering University of Science and Technology Beijing Beijing 100083 China Key Laboratory of High-Efficient Mining and Safety of Metal of Ministry of Education University of Science and Technology Beijing Beijing 100083 China

Proper room and pillar sizes are both critical factors for safe mining and high ore recovery rate in shrinkage stoping mining of underground metal mines. The rock masses of Tangdan copper mine of China are fractured, which needs much reinforcement and support prior to mining. Cement-sodium silicate grout technology was selected, then its related parameters such as grout pressure, diffusion radius and time were calculated and proposed. In order to test the effect of the pressured grout in the fractured No.4 ore block, field experiments were conducted. To optimize stoping configuration, three-dimensional numerical simulation with ANSYS and FLAC 3 D softwares was proposed. The results show that the drilling porosity and mechanical properties of the rock masses are increased obviously. After grout, ore recovery rate is increased by 10.2 % employing the newly designed stoping configuration compared with the previous. Last, analyzed from the surface movements, roof subsidence and the maximum principal stress of the pillars, the mining safety is probable of being ensured.

关键词： shrinkage stoping mining cement-sodium silicate grout effect of pressured grout stoping configuration three-dimensional numerical simulation

Contribution of CNTs/CNFs morphology to reduction of autogenous shrinkage of Portland cement paste

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Frontiers of Structural and Civil Engineering 2016年第2期10卷 224-235页

作者： Feneuil BLANDINE Karin HABERMEHI-CWIRZEN Andrzej CWIRZEN Concrete Technology Laboratory Department of Civil and Structural Engineering School of Engineering Aalto University Rakentajanaukio 4 00076 Aalto Finland Department of Civil Environmental and Natural Resources Engineering Luled University of Technology Luled Sweden

ABSTRACT In this experimental study, carbon nanotubes （CNTs） and carbon nanofibers （CNFs） were dispersed by intensive sonication in water in the presence of superplasticizer and subsequently mixed with Portland cement with water/ cement ratios varying between 0.3 and 0.4. The autogenous shrinkage in the fresh stage was investigated. The CNTs and CNFs were characterized by high resolution scanning electron microscopy （SEM） and the hydrated pastes were studied by X-ray diffraction and SEM. The results showed a reduction of the autogenous shrinkage by 50% for pastes containing small amounts （0.01 wt%） of nanomaterials. Higher additions appeared to be less effective. The highest reduction of shrinkage was observed for carbon nanofibers which were long, rather straight and had diameters of around 200 nm. The result showed that the addition of nanomaterials accelerated the hydration processes especially in the early stages of hydration. The effect was the most pronounced in the case of functionalized nanotubes. The proposed mechanism resulting in the reduction of the autogenous shrinkage was a combination of nano-reinforcing effects, alterations of hydration and microstructure of the hydrated matrix.

关键词： carbon nanotubes shrinkage cement paste

Numerical Simulation of Macrosegregation Caused by Thermal–Solutal Convection and Solidification shrinkage Using ALE Model

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Acta Metallurgica Sinica(English Letters) 2019年第11期32卷 1396-1406页

作者： Kang-Xin Chen Hou-Fa Shen Key Laboratory for Advanced Materials Processing Technology Ministry of Education School of Materials Science and Engineering Tsinghua University

Solidifi cation shrinkage has been recognized as an important factor for macrosegregation formation. An arbitrary Lagrangian–Eulerian(ALE) model is constructed to predict the macrosegregation caused by thermal–solutal convection and solidi-fi cation shrinkage. A novel mesh update algorithm is developed to account for the domain change induced by solidifi cation shrinkage. The velocity–pressure coupling between the non-homogenous mass conservation equation and momentum equation is addressed by a modifi ed pressure correction method. The governing equations are solved by the streamline-upwind/Petrov–Galerkin-stabilized fi nite element algorithm. The application of the model to the Pb-19.2 wt%Sn alloy solidifi cation problem is considered. The inverse segregation is successfully predicted, and reasonable agreement with the literature results is obtained. Thus, the ALE model is established to be a highly effective tool for predicting the macrosegregation caused by solidifi cation shrinkage and thermal–solutal convection. Finally, the effect of solidifi cation shrinkage is analyzed. The results demonstrate that solidifi cation shrinkage delays the advance of the solidifi cation front and intensifi es the segregation.

关键词： Macrosegregation Solidification shrinkage Finite element method Arbitrary Lagrangian–Eulerian(ALE)

Numerical Simulation of shrinkage Cavity Formation in Spheroidal Graphite Iron Castings Based on Micro Modeling

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International Journal of Minerals,Metallurgy and Materials 1998年第1期12卷 9-12页

作者： Wenzhen Li Baicheng Liu Shantong Jin (Metallurgy Engineering School, University of Science and Technology Beijing, Beijing 100083, China)(Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China) Metallurgy Engineering School University of Science and Technology Beijing Beijing 100083 China Department of Mechanical Engineering Tsinghua University Beijing 100084 China

A micro-modeling method (MM) for the quantitative prediction of the shrinkage cavity formation in SGiron castings is proposed. The mathematical models describing the volume changes during the solidification ofspheroidal graphite cast iron are established based on the models of solidification kinetics. The shrinkage cavityformation of T-shaped SG iron castings is calculated with MM method. The calculated results are compared with theexperimental results. It is shown that the predicted size, shape and distribution of shrinkage cavity by MM methodare in good agreement with the measured results.

关键词： solidification shrinkage numerical simulation micro modeling spheroidal graphite cast iron