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Buffer material has been shown to be effective over the long term for radionuclide diffusion retardation and is used as the final artificial barrier of the multi-barrier system in the high-level waste disposal repository. The method of disposal raises the possibility of radionuclides escaping and returning to the biosphere when ground water enters the natural geological barrier, risking the repository's long-term stability and safety. Bentonite was chosen as the basic material in the integrated buffer material due to its low permeability, high swelling, and self-healing ability. Meanwhile, attapulgite served as an auxiliary, and pyrite served as a mineral additive. The buffer material B7AP was created by combining three materials, namely bentonite, attapulgite, and pyrite, with a mass ratio of 63:27:10. The diffusion of uranium in samples with a dry density of 1.70 g/cm3 was studied using a constant source diffusion experiment. The results showed that the B7AP buffer material had a good uranium retardation effect, with an apparent diffusion coefficient of 4.07 × 10−12 m2/s. In addition, using the theory of porous media contaminant migration, a simplified convection-dispersion-adsorption equation for uranium migration on integrated buffer material B7AP was established. MATLAB software was used to simulate time scales, seepage velocity, apparent diffusion coefficient, and retardation factor. The current study provides scientific evidence for improving retardation performance, screening, and optimizing the formula design of radioactive waste repository buffer materials. [ABSTRACT FROM AUTHOR]

The filter mud in molasses has a significant inhibitory effect on biological activity and cannot be utilised by organisms; therefore, before molasses are biotransformed, the filter mud will be separated and directly discarded in the environment. In this study, the filter mud was used as the retarder of cement concrete OPC 42.5 for the first time. It was found that when 0.2–0.8% filter mud was added to fresh cement concrete OPC PC 42.5, the hardening time of cement slurry was significantly prolonged due to the synergistic retarding effect of sugar, colloid and total cellulose in the filter mud. In addition, the compressive strength of cement concrete mixed with the filter mud in the early stage (<10 days), middle stage (10–100 days) and later stage (180 days) was significantly higher than that of cement concrete and cement concrete mixed with commercial asphalt lignosulfonate. These results showed that the filter mud in molasses could realise harmless and resource utilisation, which could promote the comprehensive utilisation of molasses. [ABSTRACT FROM AUTHOR]

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The estimation of fatigue crack growth for a ship structure is a complicated subject, especially when loads vary. Several researchers studied fatigue crack growth under varying loads with simple block loads, and many models have been proposed. More research is required to properly evaluate the storm loads, representing complex actual loads a vessel experience on the sea. This study proposes a new simple fatigue crack growth model that incorporates only two parameters of the stress ratio factor and the load history factor taking account of the underload effects using empirical data in the literature. The procedures for formula modification and optimum model selection are introduced. The new model is optimized and validated by comparing it with several simple block load tests and existing fatigue crack growth models. Generally, the new model shows competitiveness and a good agreement with the experiment results. The proposed model is expected to be a potential solution, with a simple formula, to estimate fatigue crack growth under variable loads including the storm loads.

The filter mud in molasses has a significant inhibitory effect on biological activity and cannot be utilised by organisms; therefore, before molasses are biotransformed, the filter mud will be separated and directly discarded in the environment. In this study, the filter mud was used as the retarder of cement concrete OPC 42.5 for the first time. It was found that when 0.2–0.8% filter mud was added to fresh cement concrete OPC PC 42.5, the hardening time of cement slurry was significantly prolonged due to the synergistic retarding effect of sugar, colloid and total cellulose in the filter mud. In addition, the compressive strength of cement concrete mixed with the filter mud in the early stage (

This study is aimed at analysing the effect of static torsion on Mode I fatigue crack growth behaviour. Experiments have been conducted under constant torque or constant twist angle with different load ratios on SAPH440 and DP780 strip steels. The experimental results showed that the application of the static torsion or twist angle extended the fatigue life of the specimens in all cases. The fatigue life showed a positive relationship with the applied torque or twist angle until some critical value. No additional improvement in fatigue life was found after the critical value. The mechanism of the retardation due to static torsion was discussed and supported by the microscope fractography analysis. An effective stress intensity factor expression was proposed based on the fractography analysis to estimate the fatigue crack growth under constant torque in the low torque condition. The parameters introduced in the expression were found to have relationships with the dimensionless quantity related to torque, tensile load, and specimen geometry. The proposed expression achieved reliable estimates of the SAPH440 and DP780 constant torque experimental results. [ABSTRACT FROM AUTHOR]

The synthesis, characterization and properties of novel amphoteric polycarboxylate superplasticizers (PCs) are highlighted in this work. Specifically, two classes of amphoteric PCs were prepared through the addition of isobutenyl polyethylene glycol, acrylic acid and synthesized amphoteric monomer. The fluidity and fluidity retention of cement pastes containing these PCs and their adsorption behavior were investigated. In addition the cement hydration heat was measured, while X-ray diffraction and thermogravimetric behavior were also characterized. Consequently, the results indicated that these amphoteric PCs exhibited good dispersion performance and enhanced adsorption onto the cement. Furthermore, the results revealed that the PCs exerted a retardation effect during the early stages of cement hydration and subsequently accelerated this process, without affecting the subsequent cement hydration. These findings highlight the potential applications of these amphoteric PCs in concrete engineering. The PCs exerted a retardation effect during the early stages of the cement hydration, and then accelerated this process. Impressively, the presence of the PCs did not affect the subsequent cement hydration. In comparison with other PCs, PC-5 exhibited a more significant retardation effect during the early stages of the cement hydration. [ABSTRACT FROM AUTHOR]

The aim of this research work is to shed more light on performance-based design through a computational framework that assesses the residual strength of damaged plate-type configurations under overloading. Novel expressions are generated to analyze the power of crack-like stress raisers coupled with retardation effects. Analytical outcomes show that careful consideration of the overload location and crack size can be quite effective in improving safety design and failure mode estimation.

Impacts of β-cyclodextrin (β-CD) on hydration of white-Portland-cement (WPC) are studied by calorimetry, ICP-OES, TOC, TG, XRD and time domain NMR. Strong retardation effect of β-CD has been confirmed in both WPC and pure C 3 S pastes. Much stronger retardation in C 3 S pastes suggests the aluminate phases (C 3 A and ettringite) in WPC pastes mitigates the retardation effect of β-CD on C 3 S hydration, probably by adsorbing β-CD molecules and thus reducing β-CD concentration in the aqueous solution. Together with precipitation experiments of pure CH and C-S-H, it is concluded that β-CD remaining in the aqueous solution of the WPC pastes blocks CH and C-S-H formation and the induction period is remarkably extended as additional time is needed to clean up the aqueous solution by slowly formed hydrates e.g., AFt. NMR results suggest high dosage of β-CD promotes C-S-H precipitation directly in aqueous solution in acceleration period, besides the surface of cement grains. [ABSTRACT FROM AUTHOR]

The influence of flaxseed gum ( FG) on the retrogradation of maize starch ( MS) was investigated in this study. Based on the results of rapid visco-analyzer ( RVA), differential scanning calorimetry ( DSC), X-ray diffraction ( XRD), Low field nuclear magnetic resonance ( LF- NMR) and scanning electron microscopy ( SEM), FG has a retardation effect on the retrogradation of MS. With the addition increasing, the more significant the retardation effect was observed ( P < 0.05). However, when the concentration of FG was up to 0.4%, the change of retrogradation ratio showed no significant difference ( P > 0.05). FG could wrap around starch granules, suppress the recrystallisation of amylose and amylopectin, increase the water mobility and decrease the water loss. In summary, the overall results suggested that FG could be used as a natural inhibitor of the retrogradation of starch in food industry. [ABSTRACT FROM AUTHOR]

The usage of chemical admixtures, such as starch-based materials, is a common approach to addressing the thermal cracking problem of cementitious materials. Capsule-based controlled release technique enables the adjustable action time of loaded chemical admixture and thus reveals the potential on inhibiting the exothermic process of cement hydration. Three types of silica-based nanocapsules loaded with 53–63% sucrose retarder are firstly prepared by interfacial polymerization in water-in-oil (W/O) emulsion. The release characteristics of three types of nanocapsules are precisely tuned by varied preparation conditions. The effects of nanocapsules on the exothermic process of cement hydration have been investigated through calorimetry measurements. All prepared nanocapsules not only delay the appearance of the main hydration peak as the retardation effect but also reduce the maximum heat flow of the main hydration peak, to some extent, as the depression effect. The depression and retardation effects are improved with the increased dosage and slower release rate of added nanocapsules. The relationship between the two effects and the action time of loaded sucrose suggests the importance of persistently inhibiting the cement hydration over the entire accelerating and decelerating processes, which can be estimated by the time window between the action of sucrose (50% release time) and occurrence of main hydration peak. [Display omitted] • A series of controlled-release silica nanocapsules containing sucrose were successfully prepared and characterized. • The nanocapsules of diverse release behaviors affect the appearance time and maximum heat flow of the main hydration peak. • The depression and retardingretardation effects dependent on the release characteristics of nanocapsules are deeply investigated. • The inhibiting mechanism is proposed as sucrose's continuous release and adsorption onto early precipitated C-S-H. [ABSTRACT FROM AUTHOR]

The effect of PCE-type SP on zeta potential of particles, spread flow, hydration kinetics, setting time, autogenous shrinkage and chemical shrinkage of UHPC pastes is investigated, as well as the spread flow, slump life and early-age strength development of UHPC. Furthermore, the dispersing and fluid-retaining ability of SP, retardation effect of SP, physical and chemical process effects are analysed. The results show that the dispersing ability of PCE-type SP is determined by its chemical structure, which shows an exponential relationship between the flowability of pastes and SP dosages. The fluid-retaining abilities of UHPCs are sensitive to the water-to-powder ratio, while the further addition of SP will not enhance the slump life after excessing the saturation dosage. Both the adsorbed PCE and the PCE remaining in the aqueous phase contribute to retardation effect. A linear correlation between the final setting time ( t final ) and the time of maximum heat flow rate ( t Q ¨ = max ) is derived. The types and dosages of SP primarily influence the absolute chemical shrinkage of pastes within 1 day, but have a great effect on the autogenous shrinkage due to different physical coagulation and chemical process. [ABSTRACT FROM AUTHOR]

We investigated an improved Kramers-Kronig analysis (KKA) routine for measuring the dielectric function of α-Al2O3, avoiding the retardation effect arising in electron energy-loss spectroscopy (EELS). The EELS data differed from the optical data in the energy range of 10-20 eV due to the retardation effect, even though Cerenkov loss was thoroughly suppressed. The calculated differential cross-section indicates that the influence of the retardation appears at scattering angles less than 0.2 mrad in the loss energy range of 10-15 eV. Using the improved KKA routine, we obtained the correct dielectric function that agreed with the optical data. The present technique is especially useful in measuring the dielectric function by EELS with a small collection semi-angle. [ABSTRACT FROM AUTHOR]

In this study, the fatigue behavior of aluminum alloy 2024T3 v-notched specimens repaired with composite patch under block loading was analyzed experimentally. Two loading blocks were applied: increasing and decreasing at two stress ratio: R = 0 and R = 0.1. Failed samples were examined under scanning electron microscope at different magnifications to analyze their fractured surfaces. The obtained results show that under increasing blocks, the crack growth is accelerated for both repaired and unrepaired specimens. This is attributed to the increase of the loading amplitude in the second block. A retardation effect was observed for decreasing blocks loading in unrepaired specimens. However, this retardation effect is attenuated by the presence of the patch which lead to lower fatigue life for repaired specimens. [ABSTRACT FROM AUTHOR]

The effect of four industrial tea derivatives (tea polyphenols [TPS], tea water-soluble extracts [TSE], tea polysaccharides [TSS], and green tea powder [GTP]), on the retrogradation of wheat starch was investigated using texture profile analysis (TPA), differential scanning calorimetry (DSC), rapid viscosity analysis (RVA), and the α-amylase–iodine method. The addition of the four tea derivatives resulted in decreased hardness and increased cohesiveness of the starch gel as shown by the TPA test. The DSC data demonstrated an increase in the enthalpy change of starch gelatinization and a decrease in the enthalpy change of starch recrystallite dissociation. The RVA results indicated that the peak viscosity, representing the intermolecular forces of wheat starch, was reduced after addition of TPS, TSE, and TSS, respectively, but was increased by GTP. Furthermore, the half crystallization time in the Avrami equation almost doubled after the separate addition of the tea derivatives. [ABSTRACT FROM AUTHOR]

Cement-asphalt mortar (CA mortar) is an inorganic-organic composite, which combines both advantages of the mechanical property of cement and flexibility of asphalt. Therefore, it has been widely applied in high-speed railway and used as a kind of semi-flexible pavement material. Cement hydration process can affect the rheological property of fresh cement-asphalt paste as well as the mechanical and durability properties of the hardened cement-asphalt paste. Whereas, the interaction of emulsifier and cement particles will significantly affect the hydration process. Hence, the influence of emulsifier on cement hydration was investigated though measuring of setting time, hydration heat, ions concentration and electrical resistivity. It is indicated that the cement hydration process was retarded with the addition of emulsifier according to the results of the setting time and the hydration heat, and meanwhile, the hydration process was delayed gradually with the increasing dosage of emulsifier. The mechanism of the retardation effect can be attributed to the occupation of emulsifier at the active sites of cement particles, therefore, the delaying of cement hydration was further confirmed by the results of the lower ions concentration of the paste mixed with emulsifier. More specifically, for the cement mixed with emulsifier, a protective layer formed around the cement particles and this protective layer hindered the releasing of ions. As is well known, electrical resistivity is an indicator parameter which can indicate the cement hydration process and the formation of micro-structure effectively, thus, the variation law of the electrical resistivity can also reflect well the retardation effect of emulsifier on cement hydration. [ABSTRACT FROM AUTHOR]

The plasticity-induced crack shielding effect is evaluated during fatigue crack growth using transmission photoelasticity. The proposed methodology is based on the evaluation of the stress intensity factors calculated from the analysis of the isochromatic fringe patterns observed at the vicinity of a crack tip. Four different mathematical models describing the crack tip stress fields (namely models based on Westergaard’s, Williams’s, and Muskhelishvili’s equations and a new model called Christopher–James–Patterson) have been employed. Thus, a comparative study to evaluate which of the models is more suitable for fatigue crack shielding evaluation has been performed. A set of fatigue experiments on polycarbonate middle-tension specimens at different R-ratios have been conducted. Experimental results reveal the presence of plasticity-induced crack shielding on growing fatigue cracks for specimens tested at a low R-ratio. In addition, a retardation effect on the fatigue growth rate has been observed due to the shielding effect induced by the plasticity generated both at the crack tip and along the crack flanks. All these results highlight the enormous potential of transmission photoelasticity for the evaluation of plasticity-induced crack shielding on growing fatigue cracks. [ABSTRACT FROM AUTHOR]

Cross-termination in bulk reversible addition-fragmentation chain transfer (RAFT) polymerization is characterized by defining a new parameter, RM, in terms of the polymerization rates with and without an externally applied magnetic field (EAMF). For the bulk RAFT polymerization (RAFTP) of styrene (St), mediated by (2-cyano-2-propyl)dithiobenzoate (CPDB) and S-1-dodecyl-S′-(α, α′-dimethyl-α′′-acetic acid)trithiocarbonate (DDMAT), an RM of 0.534 and 0.382 is obtained respectively, showing a sensible dependence on the RAFT agent. It is also found that RM has a close relationship with the strength of the EAMF and the concentration of the RAFT agent. Detailed discussion reveals that RM can be used as a characteristic parameter to measure the extent of cross-termination in RAFTP. The experimental technique offers an efficient way to quantitatively probe the cross-termination in situ, and sheds light on the mechanism of RAFTP. [ABSTRACT FROM AUTHOR]

Co diffusion in Cu was studied by electron probe microanalysis (EPMA). The samples were annealed at the temperature range 600–800 °C (0.65–0.8 T m – Cu melting temperature). The Co concentration was measured along grain boundary (GB) in adjacent to GB region and far from it. It was shown that Co concentration does not depend on the distance from GB at the same depth. This result indicates the absence of the accelerated GB diffusion. The possible reasons for such unexpected result can be connected with the gradient of GB surface tension as the additional driving force for GB diffusion. The last effect is related the increasing of Cu GB surface tension on Co concentration. [ABSTRACT FROM AUTHOR]

Abstract: In order to prevent the initiation of a brittle crack in a marine structure, fatigue crack propagation from potentially hazardous embedded weld defects must be evaluated under the realistic seaway loading using certain clustered loading patterns. We first simulate the fatigue crack propagation under the random sequence of clustered loading so-called storm model. The numerical simulation is carried out by a method considering the plastic wake on the crack surfaces, which may cause the retardation effects after high amplitude of loading. Furthermore, fatigue crack propagation under the effect of slam-induced whipping stress is examined by a series of experiments using CT specimens and by simulations. [Copyright &y& Elsevier]

Together with an increased interest in deep petroleum and shale gas exploration over the last decade, the effects of pressure on gas generation and pore evolution in organic-rich shales have received renewed attention. In this study, miniature core plugs drilled from a thermally matured Eagle Ford Shale sample were pyrolyzed in sealed gold tubes to investigate the effects of pressure on gas generation coupled with pore evolution in the presence of a relatively intact rock fabric. The gold-tube-capsuled samples were isothermally heated at a temperature of 425 °C for 36 h under different confining pressure conditions (10, 25, 35, 50, 68, 80, and 120 MPa), with maturation being induced from the original oil window to the gas window. Experimental results show that increasing the confining pressure from 10 to 120 MPa has initially retards and then promotes the generation of low molecular hydrocarbons (C 1 –C 5 alkanes), whereas gas dryness (C 1 /C 1–5 , vol%) increases continuously from 51% to 63% in this pressure range. The inflection pressures that correspond to the maximum retardation of the generation of individual hydrocarbon compounds are shifted to higher values with increasing the molecule carbon number, e.g., 35 MPa for methane, 50 MPa for ethane to butane, and 68 MPa for pentane. Similar pressure effects have also been found for liquid hydrocarbons (C 6–14 hydrocarbons and C 14+ compounds), with a single inflection pressure of 68 MPa. These observations indicate that high pressure inhibits residual oil cracking but simultaneously favors generation of methane-rich gas. A mechanism for the interaction of retained hydrocarbons and porous matured kerogen (and/or pyrobitumen) is thus suggested to explain the enhanced methane generation. The extent of such interactions is highly dependent on petroleum expulsion efficiency from an intact rock fabric. BET specific surface area and pore volume measured by N 2 adsorption decrease significantly for samples matured at 10–35 MPa and then increase at confining pressures above 50 MPa. The simultaneous variations in pore development and methane generation with increasing confining pressure indicate that the observed effect of confining pressure on the evolution of the pore structure of shales depends on both oil retention and gas generation. Our experimental results provide some new insights into gas generation and pore evolution in shale systems, and the retardation effect of pressure on hydrocarbon generation and expulsion as well as pore evolution may provide a mechanism for the Type II kerogen-dominated oil-prone shales to become potential shale gas reservoirs. • Miniature calcareous shale plugs were pyrolyzed in gold tubes at different confining pressure. • Evolution of hydrocarbon composition was studied as a function of confining pressure. • Increasing confining pressure initially retards and then promotes HC generation. • Interaction between retained hydrocarbons and porous kerogen/pyrobitumen enhances methane generation. • Trends in pore evolution with confining pressure are similar to those of gas generation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Plasticity-corrected stress intensity factor (PC-SIF) is developed. [•] Theoretical correlation of the Paris law with crack tip plastic zone is established. [•] The overload retardation of fatigue crack growth is properly described by the PC-SIF. [Copyright &y& Elsevier]

ABSTRACT Periodic tensile overloads superposed on constant amplitude cycles were used on compact tension fracture mechanics specimens of an aluminum (Al-Cu-Mg) alloy. The delayed retardation of corrosion fatigue crack propagation in the low part of the Paris regime was investigated in a 3.5% NaCl environment. The aluminum alloy exhibits the intensive retardation effect of crack propagation under overload ratios from 1.3 to 2.0 and overload intervals from 102 to 104 cycles. The crack propagation under the periodic overloads can be treated as the base constant amplitude crack propagation, i.e. . The periodic overloads decrease the crack propagation resistance coefficient of Bcf, but have less effect on the threshold value of obtained by best fitting of this model. [ABSTRACT FROM AUTHOR]

Abstract: Fatigue strength improvement method which combined a cleaning treatment with a grinder and a peening treatment is investigated. Although a stress concentration at a weld toe is reduced by the cleaning treatment, the peening treatment does not change the stress concentration. The reduction of stress concentration at the weld toe greatly improves a crack initiation life. The peening treatment can introduce a compressive residual stress at surface layer. Since a residual stress near a crack tip for peened specimens should be compression due to a redistribution of compressive residual stress, a crack propagation rate does not retard only in the compressive residual stress region but in the tensile residual stress region. The compressive residual stress induced by the peening treatment improves the crack propagation life. [Copyright &y& Elsevier]

Abstract: Discrete linear population balance models have been widely used for comminution processes and particle breakage tests that involve a series of breakage events. The fundamental tenet of these models is the independence of particle breakage from the surrounding particle population. On the other hand, ample experimental data have shown that multi-particle interactions among particles of different sizes at the particle ensemble scale lead to a population-dependent breakage probability. In an attempt to analyze and model the multi-particle interactions, we formulate a time- or space-discrete and particle size-discrete non-linear population balance model using a recently introduced non-linear kinetics framework for rate-based comminution processes. The discrete model is developed as a limiting case and presented in equivalent matrix and index notation. The practical applicability, accuracy, and stability aspects of the model are discussed. With an empirical, flexible, non-linear functional accounting for multi-particle interactions explicitly, the proposed model can serve as a framework for quantitatively analyzing multi-particle interactions. Numerical simulations with a simplified discrete model have provided significant insight into the retardation effect of fines on the breakage probability of the coarser particles experimentally observed in dense-phase particulate systems such as particle bed compression tests. [Copyright &y& Elsevier]

Abstract: A model potential for intermolecular attractive forces, which takes into account the retardation effect at large distances, is proposed. This potential is shown to be capable of approximating arbitrary empirical potentials of intermolecular interactions. For this model potential, the generalization of the known Hamaker formula for the attractive energy of macroscopic particles is derived. A comparison of the laws of attraction of particles of spherical shapes, when the retardation effect is taken into account as realized in the model discussed, with the classical Hamaker result neglecting such dependence is carried out. [Copyright &y& Elsevier]

solution of atrazine in a TiO suspension, an endocrine disruptor in natural water, was tentatively treated by microwave-assisted photocatalytic technique. The effects of mannitol, oxygen, humic acid, and hydrogen dioxide on the photodegradation rate were explored. The results could be deduced as follows: the photocatalytic degradation of atrazine fits the pseudo-first-order kinetic well with k = 0.0328 s, and ·OH was identified as the dominant reactant. Photodegradation of atrazine was hindered in the presence of humic acid, and the retardation effect increased as the concentration of humic acid increased. HO displayed a significant negative influence on atrazine photocatalysis efficiency. Based on intermediates identified with gas chromatography-mass spectrometry (GC-MS) and Liquid chromatography-mass spectrometry (LC-MS/MS) techniques, the main degradation routes of atrazine are proposed. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the impact of the addition of β-cyclodextrin (β-CD) on bread staling was investigated by texture profile analysis (TPA), X-ray diffraction (XRD), and differential scanning calorimeter (DSC). Results showed that the retardation effect of β-CD on bread staling was found to be significant as less changes of hardness, cohesiveness and springiness were observed during the storage. The addition of β-CD also significantly decreased recrystallization rate k, and increased Avrami exponent n, indicating that the nucleation type was transformed. Investigated by X-ray diffraction, changes of crystalline patterns occurring in crust and crumb were retarded by the development of A+V and B+V intermediate patterns for stored crust and stored crumb, respectively. This retardation was attributed to the amylose–lipid–β-CD complex formation observed and analyzed by DSC technique, resulting in nucleation type transformation and lowering the rate of bread staling. [Copyright &y& Elsevier]

In this study, the impact of the addition of β-cyclodextrin (β-CD) on long-term retrogradation of rice starch was investigated by texture profile analysis (TPA), differential scanning calorimeter (DSC), and X-ray diffraction (XRD). Results showed that the addition of β-CD presented a crucial role in retarding the long-term retrogradation of starch. The present β-CD also significantly decreased crystallization rate ( k), and increased avrami exponent ( n). The increase in exponent value indicated that the addition of β-CD transformed the nucleation type due to the formation of amylose–lipid-β-CD complex. Further, the presence of β-CD produced an additional peak 5.2 Å of the gelatinized gel, and retarded crystalline type of the retrograded gel from V- to B-pattern, probably corresponding for the nucleation type transformation. [ABSTRACT FROM AUTHOR]

• The retardation effect of epoxy latexes on cement hydration is time-dependent. • Epoxy latexes slow heat-generation rate of cement hydration and suppresse heat-flow maxima. • Higher epoxy latex content leads to even slower cement hydration. • Multi-component hydration model is established for composite cementitious materials. The kinetics and thermodynamics of the retardation effect of epoxy latexes on cement hydration were investigated using isothermal calorimetry and in-situ x-ray diffraction. The experimental results showed that the retardation effect of epoxy latexes on cement hydration was time-dependent. When the epoxy latexes were added to cement pastes, heat-generation rate was slowed, the hydration induction and acceleration periods were delayed, and the heat-flow maxima were suppressed. The addition of epoxy latexes markedly retarded silicate and aluminate hydrations by retarding both the dissolution of cement clinker minerals and the precipitation of hydration products. Higher epoxy latex content led to even slower cement hydration. Based on these results, a multi-component hydration model for composite cementitious materials, considering the time-dependent retardation effect of epoxy latexes on cement hydration, was established. The numerical results showed that the model showed great potential to predict the kinetics and thermodynamics of cement hydration with different epoxy latex contents, and provided more details about the phase evolution of the clinker minerals during cement hydration. [ABSTRACT FROM AUTHOR]

Abstract: The effect of lightning channel tortuosity on the associated electromagnetic (EM) fields in the time domain is investigated quantitatively from a new point of view. Due to the vanishing of geometric symmetry when taking into account the tortuosity of lightning channels, it is necessary to calculate the associated EM fields in the Cartesian coordinate system. An efficient technique is adopted to produce tortuous lightning channels and then the fractal dimension of the channel is calculated automatically by a program. The results show that at close distances, the dependence of EM fields on azimuth is significant, the ratio of MF peaks at two coaxial points with the channel base may reach about 4 and that of the EF may be larger than 2. With increased distance, the dependence of waveform on azimuth weakens. At distances of 10 km and 100 km, the current peaks derived from the EF peaks show good consistency with the current peak adopted, with an uncertainty less than 25%. [Copyright &y& Elsevier]

Abstract: With the improvement of measurement accuracy, room-temperature creep has been observed in many metallic materials. In the present paper, a SUS304 stainless steel is selected to investigate room-temperature creep at a crack tip and its influence on subsequent fatigue crack growth. Time-dependent deformation at crack tips under constant stress intensity factor was detected at room temperature. The creep deformation is found to increase with increasing overload ratio and constant stress intensity factor. Loading conditions, such as unloading and/or reloading have a significant influence on the deformation. Compared to single wave overload, room-temperature creep under the same overload ratio produces more retardation on subsequent fatigue crack growth behavior. It is shown that crack closure plays a dominant role in this retardation effect. [Copyright &y& Elsevier]

We consider a method for deriving relativistic two-body wave equations for fermions in the coordinate representation. The Lagrangian of the theory is reformulated by eliminating the mediating fields by means of covariant Green's functions. Then, the nonlocal interaction terms in the Lagrangian are reduced to local expressions which take into account retardation effects approximately. We construct the Hamiltonian and two-fermion states of the quantized theory, employing an unconventional “empty” vacuum state, and derive relativistic two-fermion wave equations. These equations are a generalization of the Breit equation for systems with scalar, pseudoscalar, vector, pseudovector and tensor coupling. [ABSTRACT FROM AUTHOR]

Abstract: The concentration dependency of the diffusivity of a solvent in a polymer solution is derived on the basis of a free volume theory. Applying a molecular kinetics approach, the Fujita–Doolittle equation is modified. The result of numerical simulation reveals that the diffusivity of solvent in a polymer solution depends largely on both the polymer chain structure and its concentration. The applicability of the analytical expression derived is justified by fitting the experimental data for n-alkyl acetate-(poly-methyl acrylate) polymer solutions in the literature. [Copyright &y& Elsevier]

Formulae for the van der Waals attraction energy and force between a spherical particle and an infinite cylinder are derived by the method of additive summation of the pair interactions described by the potential of the general form Um=−αmρ−m. The formula of Rosenfeld and Wasan for the non-retarded vdW force between a sphere and a cylinder (m=6) is confirmed and the compact expression for the retarded force (m=7) is obtained. The comparison is given for the forces of the retarded vdW interaction between a sphere and a cylinder, another sphere, a row of spheres and a half-space. Also, the compact formulae for the energy of the vdW interaction of a point-like particle (atom, molecule) with a sphere and a cylinder are derived for the case of arbitrary m. [Copyright &y& Elsevier]

The aim of this research work is to shed more light on performance-based design through a computational framework that assesses the residual strength of damaged plate-type configurations under overloading. Novel expressions are generated to analyze the power of crack-like stress raisers coupled with retardation effects. Analytical outcomes show that careful consideration of the overload location and crack size can be quite effective in improving safety design and failure mode estimation. [ABSTRACT FROM AUTHOR]

• Biaxial fatigue crack growth is modeled using CFEM with the cyclic damage. • Effects of loading conditions on fatigue crack growth are explored systematically. • Both transverse stress and tensile overload reduce fatigue crack growth rate. • Fatigue crack growth is faster under low-high loading than high-low one. • The mechanisms of fatigue crack growth are elaborated by plastic dissipation. During the operation of proton exchange membrane in fuel cells, cyclic mechanical loads are introduced due to the humidity cycles. The resulting fatigue crack is known to be the main source for its mechanical degradation. In this paper, we use a relation between damage evolution of the cohesive elements and Paris law to simulate the biaxial fatigue crack growth. The effects of various loading conditions are investigated. The predicted crack growth is in a good agreement with experimental studies. Both the transverse stress and the tensile overload have retardation effects. It is also found that the fatigue crack growth rate associated with a shorter pre-crack depends more on the load waveform. Moreover, fatigue crack grows faster under the low-high loading history than the high-low one. These simulation results have provided significant insights into the fatigue failure behavior of membranes during operation conditions and can help improve their durability. Image, graphical abstract [ABSTRACT FROM AUTHOR]

As the most effective superplasticizer, the comb-like PCE polymers also severely retard early cement hydration and hence decelerate early strength growth of concrete, which is undesired in some applications. In this study, a series of PCEs with different molecular architectures, including varied side chain length and density were synthetized by co-polymerizing acrylic acid and α-methallyl-ω-hydroxy poly(ethylene glycol) ether. Impacts of the obtained PCEs on cement hydration and early strength of mortar were investigated. Results show that adsorption of PCEs on cement grains is highly dependent on polymer architectures. Higher side chain length and density lead to lower adsorption amount and consequently higher early strength of mortar. It is interestingly found that the retardation effect of the PCEs on cement hydration is simply proportion to their absolute adsorption amounts on cement surface, while the complexation of R−COO− group with Ca2+, which is independent on polymer architectures, plays a minor role. [ABSTRACT FROM AUTHOR]

Abstract: The spectral properties of spin–charge separation in one-dimensional electron–phonon interacting systems are investigated through the calculation of one-electron spectral functions of one-dimensional Holstein model away from half-filling. It is found that the retardation effect reduces weights of both spinon and holon collective excitations and increases the incoherent spectral weight at the same time, which makes the spin–charge separation invisible in the spectral function. Some differences between the spectral functions of the model at different filling are also discussed. [Copyright &y& Elsevier]