Numerical modeling of shrinkage induced cracking in cementitious materials with three-dimensional simulation and phase-field method

Modeling rapid self-sealing of cracks in cementitious materials using superabsorbent polymers

A probabilistic analysis of acoustic emission events and associated energy release during formation of shear and tensile cracks in cementitious materials under uniaxial compression

Research progress on the self-healing mechanism and technology of cracks in cementitious materials

Three-dimensional PD-FEM coupled simulation of drying shrinkage cracking in cementitious materials: Mechanisms and aggregate effects

Improving the durability and sustainability of concrete structures has been driving the enormous number of research papers on self-healing mechanisms that have been published in the past decades. The vast developments of computer science significantly contributed to this and enhanced the various possibilities numerical simulations can offer to predict the entire service life, with emphasis on crack development and cementitious self-healing. The aim of this paper is to review the currently available literature on numerical methods for cementitious self-healing and fracture development using Phase-Field (PF) methods. The PF method is a computational method that has been frequently used for modeling and predicting the evolution of meso- and microstructural morphology of cementitious materials. It uses a set of conservative and non-conservative field variables to describe the phase evolutions. Unlike traditional sharp interface models, these field variables are continuous in the interfacial region, which is typical for PF methods. The present study first summarizes the various principles of self-healing mechanisms for cementitious materials, followed by the application of PF methods for simulating microscopic phase transformations. Then, a review on the various PF approaches for precipitation reaction and fracture mechanisms is reported, where the final section addresses potential key issues that may be considered in future developments of self-healing models. This also includes unified, combined and coupled multi-field models, which allow a comprehensive simulation of self-healing processes in cementitious materials.

Two- versus three-dimensional direct simulations of turbulent methane flame kernels using realistic chemistry

Evaluation of the diffusion coefficient of cement paste from pore size distribution using three-dimensional simulation

Aerostatic spindles offer low heat generation and high rotation accuracy, which make them an ideal choice for ultra-precision drum lathe, where extremely high motional accuracy and thermal stability are required. However, the limitations such as insufficient load capacity and stiffness have restricted their permissible application range and make them not suitable for large ultra-precision machine tools including drum lathe. In order to improve the load capacity and stiffness, this paper presents a high load capacity aerostatic spindle with pocketed orifice-type restrictors. Fluent is adopted and three-dimensional simulation models of aerostatic spindle with orifice and feeding pocket are set up to analyze the load characteristics. The simulation results show that this restrictor can enhance the throttling effect of orifice and suppress the pressure drop away from the orifice. Moreover, for aerostatic journal bearing, when eccentricity ratio is in the range of 0.2–0.3 and gas supply pressure is 0.6 MPa, carrying capacity and stiffness can reach up to 9499.4 N and 2813.1 N/μm. Finally, a group of loading experiments are carried out which prove that the novel three-dimensional simulation method is feasible and accurate to calculate the load characteristics of aerostatic spindles.

This paper presents a new parallel algorithm and performance results of iterative solution methods for three-dimensional MOSFET simulation with Gummel's method. A splitting-up operator method is proposed for incomplete factorization of sparse matrices arising from semiconductor device equations, suitable for parallel computations. This method is combined with the conjugate gradients and BiCGSTAB procedure to obtain a new parallel version of the iterative solution methods. Natural parallelism is realized by developing the solution method according to the natural ordering. In large-scale simulations of greater than 100000 grid nodes, the high parallel efficiency level over 90% can be achieved using a new-type massively parallel computer: ADENART with up to 256 processors. The real performance of the solution methods is superior to those calculated by the vectorized version of the ICCG and ILUBiCGSTAB methods using a vector-type supercomputer.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In order to improve the efficiency and accuracy of numerical simulation of gravity anomalies in large-scale complex models, this paper proposes a method for three-dimensional numerical simulation of gravity anomalies under arbitrary terrain, and implements its CPU-GPU parallel acceleration scheme. By performing a two-dimensional Fourier transform along the horizontal direction, three-dimensional partial differential satisfied by gravitational potential are transformed into one-dimensional ordinary differential equations in different wavenumbers, reducing computational and storage requirements. Moreover, the ordinary differential equations in different wavenumbers are independent of each other and have good parallelism. By retaining the vertical direction as the spatial domain and introducing traveling wave decomposition, the effects caused by upper and lower boundaries are eliminated. The vertical grid is arbitrary. A two-dimensional quasi-complete information Fourier transform is utilized to enhance both the accuracy and efficiency of the Fourier transform process, allowing both uniform and non-uniform flexible sampling. Based on the high parallelism, one-dimensional ordinary differential equations are solved in parallel using CPU, and quasi-complete information Fourier transform are computed in parallel using GPU. An abnormal sphere is designed to analyze the wavenumber spectral distribution characteristics of the anomalous potential and summarize the wavenumber sampling rules. The logarithmic uniform sampling in the wavenumber domain has high accuracy. Compared with Gauss-FFT, the quasi-complete information Fourier transform selects fewer wavenumbers and exhibits higher accuracy. The computational efficiency is greatly enhanced through the use of single-precision CPU-GPU parallel scheme, and a model with tens of millions of nodes only takes a few seconds. Two terrain models are designed to verify the algorithm’s adaptability to arbitrary complex terrains. This is significant for achieving fine inversion imaging and interpretation of gravity anomalies under large-scale complex conditions.

Optimum designs of cell configuration and polycrystalline silicon (poly-Si) grown by atmospheric pressure chemical vapor deposition (APCVD) have been demonstrated. In order to realize high-efficiency thin film poly-Si solar cells, a novel method of quasi three-dimensional simulation using a cylindrical coordinate system was carried out. Grain boundaries interface recombination velocity based on the simulation should be less than 10/sup 3/ cm/s. Even at a relatively short diffusion length of L/sub n/=50 /spl mu/m, high efficiency larger than 16% will be expected at a thickness of 5-20 /spl mu/m. Poly-Si films with columnar diameter of around 5 /spl mu/m were successfully deposited on foreign substrates with APCVD at a high growth rate of 0.8 /spl mu/m/min.

Abstract— Twenty‐four refractory inclusions (40–230 μm, with average of 86 ± 40 μm) were found by X‐ray mapping of 18 ordinary chondrites. All inclusions are heavily altered, consisting of finegrained feldspathoids, spinel, and Ca‐pyroxene with minor ilmenite. The presence of feldspathoids and lack of melilite are due to alteration that took place under oxidizing conditions as indicated by FeO‐ZnO‐rich spinel and ilmenite. The pre‐altered mineral assemblages are dominated by two types: one rich in melilite, referred to as type A‐like, and the other rich in spinel, referred to as spinelpyroxene inclusions. This study and previous data show similar type and size distributions of refractory inclusions in ordinary and enstatite chondrites.A survey of refractory inclusions was also conducted on Allende and Murchison in order to make unbiased comparison with their counterparts in other chondrites. The predominant inclusions are type A and spinel‐pyroxene, with average sizes of 170 ± 130 μm (except for two mm‐sized inclusions) in Allende and 150 ± 100 μm in Murchison. The relatively larger sizes are partially due to common conglomerating of smaller nodules in both chondrites. The survey reveals closely similar type and size distributions of refractory inclusions in various chondrites, consistent with our previous data of other carbonaceous chondrites. The petrographic observations suggest that refractory inclusions in various groups of chondrites had primarily formed under similar processes and conditions, and were transported to different chondrite‐accreting regions. Heterogeneous abundance and distinct alteration assemblages of refractory inclusions from various chondrites could be contributed to transporting processes and secondary reactions under different conditions.

The order noise in low-frequency band has great impact on the sound quality of exhaust noise. The muffler with valve becomes one of the means to eliminate low-frequency noise. The actual muffler with valve is analyzed by experiment and three-dimensional numerical simulation methods. It is found that the resonance frequency shift towards high frequency as the valve's opening degrees increase. Further, a sub structural unit, named adjustable lumped inertance resonator(ALIR), is extracted from the actual muffler with valve. Three-dimensional numerical simulation and an in-line lumped element model are used to calculate the lumped inertance of the valve structure with different opening angles. The lumped model of ALIR is established. The results show that the lumped inertance, which changes with the valve's opening degrees, is the key factor on the shifting of resonance frequency. Therefore the low frequency silencer mechanism of the muffler with valve is successfully revealed. At last, actual vehicle test is implemented with the muffler with valve and a contrast muffler. It is found that the muffler with valve can effectively eliminate the order noise tracing the engine speed times.

Modeling the uncoupled damage-healing behavior of self-healing cementitious material with phase-field method

Due to economic, environmental and technical benefits, one of the most widespread applications of natural zeolites is to be found in the cement and concrete industry. Application of natural zeolite in the manufacture of pozzolanic cements began from the first decades of the 20th century and shows a growing trend in recent decades. Use of natural zeolite as a supplementary cementitious material in the production of cement, mortar and concrete has been investigated in many studies. Generally, it is shown that the use of natural zeolite leads to the improvement of mechanical strength and durability properties of cement and concrete composites. In addition to pozzolanic properties, some other characteristics of natural zeolites have made them useful in special applications. This chapter aims to review the characteristics of natural zeolites and their effects on the engineering properties of cement and concrete composites.