Showing papers by "Tongji University published in 1987"
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TL;DR: The applicability of linear elastic fracture mechanics to a composite material such as concrete has always been questioned as discussed by the authors, but little work has been done to determine experimentally major influences on these material parameters.
Abstract: The applicability of linear elastic fracture mechanics to a composite material such as concrete has always been questioned. Recently, a new approach to describe failure of concrete has been developed. In this context a material is characterized by its fracture energy and the shape of the descending branch of the strain softening diagram. So far little work has been done to determine experimentally major influences on these material parameters. In this contribution results of test series to study the influence of age of loading, water-cement ratio, and rate of loading are presented. It is shown that a detailed evaluation of the test data necessitates appropriate computer programs. Essentials of these modules are briefly described. It is shown that failure of a beam under three-point bending mode can be predicted in a realistic way if valid material parameters are incorporated in a numerical analysis. Finally, it is pointed out that further studies are needed before a general application of the new approach can be recommended.
126 citations
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TL;DR: A study of the structure of the interfacial zone developed at the marble-C3S interface revealed the existence of a thin "duplex" layer right at the rock surface followed by a C3S paste region with gradually decreasing portlandite content as mentioned in this paper.
42 citations
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TL;DR: In this paper, the authors studied the mechanism of the formation of a structure within the marble - portland cement interfacial zone and its relationship to bond strength. And they found that a carboaluminate layer at the rock-cement paste interface was found to be beneficial for the bond strength while an excessive carbonate dissolution and subsequent precipitation of portlandite at the interface affects the existing bond adversely.
38 citations
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TL;DR: In this article, the influence of the matrix-aggregate bond on the strength and brittleness of concrete is studied, in terms of energy dissipation and crack propagation during failure of concrete.
Abstract: In this paper, the influence of the matrix-aggregate bond on the strength and brittleness of concrete is studied. Six different matrixaggregate interfaces are used to evaluate the interfacial bond capability. The results obtained on the strength and brittleness index of concrete show that strengthening and toughening of concrete can be obtained simultaneously, if the interfacial bonds are changes so that they conform to a rational distribution according to aggregate size. These results are discussed in terms of the energy dissipation and crack propagation during failure of concrete.
31 citations
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TL;DR: In this paper, the authors give a new proof of the sharp upper bound for the indices of convergence of n x n irreducible Boolean matrices with period p, and characterize the matrix with the largest index.
19 citations
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TL;DR: In this paper, the results of XRD, SEM and EPM microhardness showed that there are heavier concentration of ions, with finer crystals and a lower degree of CH orientation at the interfacial zone between steel slag particles and cement paste.
Abstract: The ordinary fine aggregate in concrete has been replaced by ground and sieved steel slag fine aggregate, treated and exposed to air for three months. Compared with concrete made from natural sand, properties such as compressive strength, flexural strength, elastic modulus, permeability and abrasion resistance are considerably improved. The improvement increases with a decrease in w/c ratio, an increase in curing time and an increase in the replacement weight of sand. These results are due to the fact that the steel slag contains some active minerals such as C 3 S, C 2 S, C 4 AF, etc., and shows favorable surface physical characteristics that improve the bond between steel slag particles and cement paste. The results of XRD, SEM and EPM microhardness showed that there are heavier concentration of ions, with finer crystals and a lower degree of CH orientation at the interfacial zone between steel slag particles and cement paste. The study also found small cementitious and fibrous C-S-H crystals growing from the fine aggregate, which are linked with hydrated products from cement paste making the bond and structural characteristic more favorable with cement. The steel slag fine aggregate is an active mineral similar to cement. The bond between the aggregate and cement paste is strengthened both physically and chemically.
18 citations
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TL;DR: In this paper, the relationship between interfacial bond and mechanical behaviour of concrete in the light of both theoretical and experimental research on the microstructure of the interfacial zone is studied.
Abstract: Concrete is a composite material, consisting of hardened cement paste (HCP), aggregate and pores. The interfacial bond between HCP and aggregate is very important in determining some of the properties of concrete, such as the mechanical behaviour and durability. Recently, the microstructure of the transition zones between different aggregates and HCP has been studied and a mechanism for the formation of the transitional zone has been proposed by Maso. The objective of the present work has been to study the relationship between interfacial bond and mechanical behaviour of concrete in the light of both theoretical and experimental research on the microstructure of the interfacial zone.
8 citations
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TL;DR: In this article, an ultrasonic topography of LiNbO3-crystals with Fe++-impurities has been shown to be obtained by means of ultrasonic experiments, where the authors observed that the elastic inhomogeneities before illumination lead to a non-exponential decay of the ultrasonic echo pattern.
Abstract: By means of ultrasonic experiments we have observed in Fe-doped LiNbO3-crystals elastic inhomogeneities and an ultrasonic absorption which stronglydecrease under laser illumination. The elastic inhomogeneities before illumination lead to a non-exponential decay of the ultrasonic echo pattern. The corresponding variations of the acoustic velocity and absorption across the sound beam have been displayed directly by an ultrasonic “topography”. — In contrast to the photorefractive behaviour of LiNbO3 the elastic inhomogeneities and the ultrasonic absorption are not enhanced but disappear as soon as the illumination is switched on: Under illumination the echo pattern becomes well exponential as expected for an ideal crystal. The physical nature of the elastic inhomogeneities and the acoustic absorption inside the sample which can be “bleached out” by optical radiation is not yet well understood. But there is evidence that Fe++-impurities play an important role.
6 citations
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TL;DR: In this article, the impact process between a flat-ended rigid body and a column with a rectangular cross-section has been investigated by using split disc for the rigid body, with the two halves bonded together and electrically insulated from each other.
4 citations
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TL;DR: In this article, a matrix resolvent operator in Liouville space is used to combine first and second order dynamic susceptibilities for a set of observables, and a well-defined triangular projector is introduced to rewrite second order susceptibilities in terms of frequencies and memory functions.
Abstract: Combined first and second order dynamic susceptibilities for a set of observables are expressed by a matrix resolvent operator in Liouville-space. A well-defined triangular projector is introduced to rewrite second order susceptibilities in terms of frequencies and memory functions. For these a Markovian type of approximation is established and connected with quantities of first order response.
3 citations
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TL;DR: The interfacial zone between cement paste and embedded steel is a porous one to which the rust can easily diffuse and where it can be deposited as mentioned in this paper, and strengthening the zone makes the passive oxide film more complete, and harder to rupture; the rate of corrosion decreases, the initiation stage of pitting corrosion is delayed, the effect of self-catalysis is weakened, and the acceleration of corrosion is greatly decreased.
Abstract: The interfacial zone between cement paste and embedded steel is a porous one, to which the rust can easily diffuse and where it can be deposited. Strengthening the zone makes the passive oxide film more complete, and harder to rupture; the rate of corrosion decreases, the initiation stage of pitting corrosion is delayed, the effect of self–catalysis is weakened, and the acceleration of corrosion is greatly decreased. Therefore, a strengthened interfacial zone can improve the anti–corrosion properties greatly, with less cost than other methods of inhibiting corrosion.
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TL;DR: In this paper, a SUGRA-GUT E 6 model with an SU(N, 1) invariant Kahler potential was presented, in which the strong CP violation can be eliminated via the invisible axion mechanism.
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TL;DR: In this article, a modified Green-Schwarz covariant supersymmetric string action was used to construct a free four-dimensional string, which is tachyon-free, ghost-free and Lorentz invariant.
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TL;DR: In this paper, the authors discuss the dynamic response of thin plates on the elastic foundations due to the moving loads by means of the variational calculus and take the mass of moving loads into account, treat a series of questions such as the forced oscillations, the influence surfaces of the flexions, the inner forces, resonance conditions and critical speed and so forth.
Abstract: This paper discusses the dynamic response of thin plates on the elastic foundations due to the moving loads by means of the variational calculus. In the text we take the mass of moving loads into account, treat a series of questions such as the forced oscillations, the influence surfaces of the flexions and the influence surfaces of the inner forces, resonance conditions and critical speed and so forth.
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01 Jan 1987TL;DR: In this article, a split-D tension test of the circular ring cut from a cylindrical vessel was used to predict the burst pressure of a FRP pipe or a cylinder vessel, which satisfactorily agrees with the hydrostatic pressure of the pipe.
Abstract: The purpose of this paper is to illustrate how to predict the burst pressure of a FRP pipe or a cylindrical vessel, using the split-D tension test of the circular ring cut from them. Two modification factors must be regarded. The first one results from the additional bending stress in the region near the mid-plane. Two new mechanical models are suggested for calculating the bending stress mentioned above. The second factor is the influence of the material’s variability, which also results in the differences of the experimental data between the ring and the pipe. After considering these two factors, we give the predicted value from the split-D test of the ring, which satisfactorily agrees with the hydrostatic pressure of the pipe.
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TL;DR: In this article, the structure of molten LiF-KCl solution has been simulated by Monte Carlo method and the partial radial distribution function of ions, the molar volume,enthalpy and the heat of mixing of LiF -KCl melt have been calculated.
Abstract: The structure of molten LiF-KCl solution has been simulated by Monte Carlo method.The partial radial distribution function of ions,the molar volume,enthalpy and the heat of mixing of LiF-KCl melt have been calculated. Some results of calculation agree with experimental data.The results of calculation indicate that the average distance between Li~+ and F~- ions decreases significantly after the mixing of molten LiF with KCl, and the free volume distribution of the LiF-KCl melt is far from uniform.
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TL;DR: In this paper, the Brillouin scattering studies on single crystals of monoclinic LAP have been presented, and the curves of the reciprocal velocity and the acoustic velocity as a function of temperature are given.
Abstract: This is the first report representing Brillouin Scattering Studies on single crystals of monoclinic LAP, which is a new organic material very useful for secondary harmonic generation. The crystal elastic constants were evaluated from the measured data. The curves of the reciprocal velocity and the acoustic velocity as a function of temperature are given here.
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TL;DR: In this article, the authors applied the selfconsistent phonon theory and the coherent potential approximation method to investigate the displacive ferroelectric phase transitions occurring in the ternary solid solution.
Abstract: The self-consistent phonon theory and the coherent potential approximation method are applied to investigate the displacive ferroelectric phase transitions occurring in the ternary solid solution. Especially, the substitutional disordered phonon system with both random diagonal and off-diagonal interactions has been dealt with and numerical computation has been made under different strengths of the atomic coupling. The results show that the interactions between different atoms greatly influence the properties of phase transitions in solid solutions and the anomalous relation between dielectric constant versus temperature can be explained. The new approach is shown to be able to offer a much more detailed description for the various solid solution systems.
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TL;DR: In this paper, the problems of combined longitudinal and lateral bending of rectangular plates which are supported at four points of corners by means of the variational calculus are discussed, and the lateral bending and the stability of thin plates are also treated respectively.
Abstract: This paper discusses the problems of combined longitudinal with lateral bending of rectangular plates which are supported at four points of corners by means of the variational calculus. In the text the lateral bending and the stability of thin plates are also treated respectively.
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TL;DR: In this paper, the authors studied the initial value problems on the infinite interval and proved that (1.1) degenerates regularly provided (ξ(e), η(e))∈SR(e).
Abstract: In this paper we study initial value problems on the infinite interval:
$$\left. {\begin{array}{*{20}c} {\frac{{dx}}{{dt}} = f(t, x, y; \varepsilon ),} & {x(0, \varepsilon ) = \xi (\varepsilon )} \\ {e\frac{{dy}}{{dt}} = g(t, x, y; \varepsilon ),} & {y(0, \varepsilon ) = \eta (\varepsilon )} \\ \end{array} } \right\}$$
(1.1)
wherex, ƒ∈Em, y, g∈En,eare real small positive parameters,0ť+∞.On condition thatgy(t)is nonsingular and under other assumptions, we have proved that there are serial (k+m*)-dimensional manifolds {SR(e)}∈Em+nsuch that (1.1) degenerates regularly provided (ξ(e), η(e))∈SR(e).Besides, the R-order asymptotic expansions of solutions are constructed, and their errors are estimated.
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TL;DR: In this paper, the problems of unsymmetrical bending of cantilever rectangular plates under various loads by the energy method were discussed and several calculating examples such as the plates which are subjected by the concentrated forces or concentrated couples unsymetrically on free sides and corner points and by a uniformly or non-uniformly distributed loads un symmetric on free edges and so forth.
Abstract: This paper discusses the problems of the unsymmetrical bending of cantilever rectangular plates under various loads by the energy method. We illustrate numerous calculating examples such as the plates which are subjected by the concentrated forces or concentrated couples unsymmetrically on free sides and corner points and by a uniformly or nonuniformly distributed loads unsymmetrically on free edges and so forth.