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The soil water retention curve is one of the most important characteristics of unsaturated soils, and it has a great relationship with soil permeability and mechanical characteristics. The laboratory measurement of the soil retention curve is quite a time consuming and expensive. In this article, four models, namely the Brooks-Corey (Hydrology Papers 1964) model, the van Genuchten (Soil Sci Soc Am J 44:1980) model, the Tyler-Wheatcraft (Soil Sci Soc Am J 53:1990) model, and the Rieu-Sposito (Soil Sci Soc Am J 55:1991) model, were introduced to predict the water retention curve based on the pore fractal dimension calculated from soil microstructure images with different magnifications. The four model predicted results were compared and discussed based on the root mean square error (RMSE) value. Results showed that the pore fractal dimension decreased with increasing magnification. The van Genuchten (Soil Sci Soc Am J 44:1980) model gives a better and more consistent prediction compared with other models. It proved that the van Genuchten (Soil Sci Soc Am J 44:1980) model is efficient for soil water retention curve prediction based on soil microstructure images analysis. [ABSTRACT FROM AUTHOR]

In this paper, we aim to clarify microstructure of bentonite from Cerny vrch deposit in the Czech Republic. We adopt results of ESEM and MIP experiments performed at various suctions along wetting and drying paths on bentonite samples compacted from powder to two different initial dry densities. The data were used for quantification of fractal dimension characteristics of pores of different sizes. Two different methods of calculating fractal dimension were used for MIP data, and one method was used for evaluation of ESEM images. Fractal dimensions obtained from MIP data, combined with the measured pore size density functions, allowed us to identify two different pore families: micropores and macropores. Macropores can be further subdivided into fine macropores and coarse macropores based on fractal analysis. The pore systems were further distinguished by different responses to suction changes and to compaction effort. In general, we observed slight increase in fractal dimension with increasing suction and with increasing dry density. [ABSTRACT FROM AUTHOR]

In this paper, the microstructure of the Czech bentonite B75 was investigated by three methods: water retention curve (WRC) measurements, mercury intrusion porosimetry (MIP) measurements and environmental scanning electron microscopy (ESEM) investigation. The experiments were performed on samples at various compaction levels (between 1·27 and 1·90 g/cm3) and at various suctions (between 3·3 and 290 MPa) along both drying and wetting hydraulic paths. In the ESEM observations, target relative humidities (and thus total suctions) were imposed directly in the ESEM chamber to observe the effect of the hydraulic path on the microstructure. Apart from the inter-lamellar pores, which are not accessible to the adopted experimental techniques, two pore families were identified: micropores and macropores. The transition pore size between the micropores and macropores was found to be suction dependent. The microporosity was practically insensitive to compaction and only the largest micropores were sensitive to suction. Smaller macropores were sensitive to compaction only, whereas larger macropores were sensitive to both compaction and suction. It was observed that, during wetting from the as-compacted state, the macropores remained completely dry up to very low values of suction, whereas the micropores were found to be unsaturated up to the suctions between 10 to 60 MPa. Both macropores and micropores contributed to sample volume changes during drying and wetting. Although the microstructural volume change appeared to be reversible, the macrostructure exhibited permanent deformation. [ABSTRACT FROM AUTHOR]

Compacted bentonite is often utilized as a buffer material between the canister containing radioactive waste and the host rock in deep geological repositories. Extremely low permeability and a potential to swell and develop large swelling pressures upon hydration are desirable characteristics for such material. This study focused on the B75 bentonite, a Ca-Mg-montmorillonite-rich clay selected as a potential buffer material for the planned repository in the Czech Republic. The effects of the initial dry density, vertical load, and pore fluid salinity on the swelling behavior of the clay were investigated. One-dimensional swelling tests were performed on compacted samples prepared at various initial dry densities (1.25–1.95 g/cm3). Conventional oedometer tests with various hydration and stress paths were also performed. An empirically corrected diffuse double layer model proved successful in predicting the swelling pressure during the tests. Swelling under constant load, swelling pressure under constant volume, swelling upon unloading, and unconfined swelling upon hydration were compared, and a unique relationship was found between the effective stress and the dry density at saturation. • Constant-load swelling tests were performed on the Czech B75 bentonite. • Swelling strains were smaller under larger loads and lower dry densities. • Hydration with NaCl solutions decreased the swelling capacity. • Swelling pressures were predicted by a modified diffuse double layer model. • Logarithm of effective stress and dry density at equilibrium were linearly related. [ABSTRACT FROM AUTHOR]

When a shock wave impacts a roughened metal/gas interface, metal ejecta particles emit and transport in the gas. The exchanges of momentum and energy between ejecta particles and the gas occur. If active metal particles transport in the reactive gas, the heat released by a chemical reaction could change these exchanges. In this paper, we use numerical simulations to study solid cerium ejecta transporting in a vacuum, and in non-reactive and reactive gases. In vacuum, the emitted ejecta could self-similarly expand neglecting the particle interaction. In the non-reactive gas (He), ejecta particles slow down by the gas resistance and have the exchanges of momentum and energy with the gas. In the reactive gas ( D 2 ), the ejecta particles also slow down. The exothermic reaction could induce the temperature rise of the ejecta and the gas, which could induce changes in physical property values of the gas after the shock wave and the velocity of the shock wave. The numerical result shows that the maximum temperature of the ejecta may appear in the middle of the mixture zone, which may result from the ejecta temperature being controlled by two competitive effects. Furthermore, the maximum ejecta temperature increases rapidly in the beginning and then becomes steady. Finally, the ejecta with a different initial size distribution is investigated. The ejecta with a smaller maximum size has a larger maximum particle temperature, a larger gas temperature after the shock wave, and a larger chemical reaction function of the ejecta at the same moment. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the ejection production from twice-shocked Sn using molecular dynamic simulations in regimes where the metal undergoes complete shock melting after the first shock. A new description form of a bubble shape is proposed to fit the interface during the whole stage, which overcomes the inapplicability of the flycut profile in later stages. We then explore the ejection on second shock with the dimensionless intervals of ∼3.8 and ∼96 between the two shocks. Surprisingly, the results show that the ejecta model can well predict the second ejecta mass with a shock interval of ∼3.8 while far underestimated that with a shock interval of ∼96. We find that in the presence of the first ejecta, the high-speed secondary interface interacts with the low-speed first ejecta, resulting in the movement of liquid metals to the secondary ejecta, thereby promoting the increase of secondary ejecta mass. These findings are further validated by our smoothed particle hydrodynamics simulations at a macroscale. [ABSTRACT FROM AUTHOR]

With the sustainable development of remote sensing satellite observation technology, the effectiveness of the remote sensing satellite observation scheme has drawn wide attention in recent years. A suitable evaluation model can provide a credible improvement basis and guide observation technology's continuous development. In this study, we present an original method based on granular computing to evaluate the remote sensing satellite observation schemes by employing intuitionistic linguistic preference relation, which is ideal for allowing evaluation team members to depict their actual opinions. The granulation of the intuitionistic linguistic preference relation is regarded as an optimization problem, solved by using the particle swarm optimization. The optimization criterion comprised of consensus and consistency is maximized by a suitable mapping of the intuitionistic linguistic preference relation on information granules. Once the granulation of the intuitionistic linguistic preference relation is completed, the solution to the evaluation problem is constructed by the selection process in virtue of the dominance levels of observation schemes and the prioritization relationship of evaluation team members. Finally, an experimental example about the evaluation of remote sensing satellite observation schemes is reported to support the feasibility and practicality of the proposed evaluation method. Furthermore, comparative analysis with other methods is also analyzed to further demonstrate the performance of the designed method. [ABSTRACT FROM AUTHOR]

Thermo-hydro-mechanical coupling is relevant in various natural processes and engineering applications involving clay soils. It can affect slope deformations and stability, as well as the functioning of clay barriers and energy piles. Temperature changes can alter the water retention capacity of expansive clays and, in turn, produce pressure, strength, and volume changes. In deep geological repositories, for instance, the design of bentonite buffers and the study of their interaction with the host formation must account for the heat released by radioactive decay. Here, to investigate how temperature controls the water retention capacity, vapor transfer experiments under adsorption/desorption (wetting/drying) paths were performed on the Czech B75 bentonite. The tests were conducted in a wide range of temperatures (20–80°C) and initial dry densities (0.6–1.9 g/cm3), at high total suction (4–400 MPa), without mechanical loads. The results showed a systematic loss of water retention capacity at high temperature, particularly at low suction, irrespective of the initial compaction. To predict the behavior at any temperature, a model was constructed from the Clausius–Clapeyron and the Guggenheim–Anderson–de Boer equations. It was calibrated and validated at various temperatures, also on a different bentonite (without further tuning), showing good performance. Dry density-specific calibrations did not affect the model predictions significantly, consistently with results that exclude an effect of initial compaction on water retention at high suction. The proposed model seems suitable for inclusion into thermo-hydraulic descriptions in comprehensive constitutive frameworks for expansive clays, potentially improving the understanding of some behaviors related to thermo-hydro-mechanical coupling. • Vapor transfer experiments at 20–80°C were performed on the Czech B75 bentonite. • The water retention capacity decreased significantly at high temperature. • Initial compaction did not affect water retention at high suction. • A thermodynamic model was able to simulate the behavior at any temperature. • The model seems suitable for improving comprehensive constitutive formulations. [ABSTRACT FROM AUTHOR]

Droplet impingement is a widespread phenomenon in nature and industrial production. Different from the problem of light drop/wall impact, which has been investigated early and sufficiently, few researches are found on the dynamic behavior and modeling of heavy drop impingement, which is widely existed in the field of plasma spray, 3D printing and ejecta mixing caused by detonation, etc. In this paper, the behavior of different metal drops impinging on dry smooth wall is studied based on Smoothed Particle Hydrodynamics (SPH) method. A newly splash threshold is proposed for heavy drop impact, and the difference of splash criteria between light drop and heavy drop is analyzed. The results show that incident kinetic energy is an important factor to determine the outcomes of heavy droplet impact. When the incident kinetic energy is relatively low, the metal droplet would spread, and the maximum spreading radius increases with the increase of kinetic energy. With higher incident kinetic energy, the droplet would splash, and the proportion of secondary droplets increases with the increase of incident kinetic energy. Higher droplet viscosity will hinder its spreading, but when splash occurs, it will promote the increase of secondary droplet. The increase of surface tension would suppress droplet spreading rate, but it has little effect on the maximum spreading radius. The splash criteria of heavy droplet impinging on dry smooth wall is proposed as K = O h ⋅ R e 1. 5346 = 3341. 95. The splash threshold of heavy droplet is higher than that of light droplet within the range of Re < 4000, owing to the higher surface tension of heavy droplet. When Re > 4000, the outcomes of light droplet impact show strong randomness, thus no uniform splash threshold can be found, while the metal droplet has a uniform splash threshold within the range of Re <100000. • The outcomes of different metal drop impingement are studied based on SPH method. • The splashing of heavy drop impingement can be judged by K = O h ⋅ R e 1. 5346 . • Differences between the criteria of heavy drop and light drop impact are analyzed. [ABSTRACT FROM AUTHOR]

Dynamic tensile (micro-spallation) fracture and subsequent recompression in a molten state is the key physical process for metallic materials undergoing multiple intense dynamic loadings. However, there still lacks in-depth analysis of the complete evolution process from damage accumulation to recompression, as well as the influence of damage history on subsequent deformation and fracture. In the present work, the mechanism of cooperative competition evolution between the melt-phase and voids has been proposed as a new perspective to investigate damage evolution. Various important physical phenomena discovered in larger-scale MD simulations of molten aluminum can be self-consistently explained according to the proposed mechanism, such as the rate-dependence of spall strength and the pressure oscillation. The recompression-after-damage and second fracture process are discussed in detail to analyze the damage history effect. Under the present framework, two theoretical models have been proposed from the perspective of void and melt-phase evolution, respectively. The proposed models agree well with the simulation results and provide a comprehensive understanding of the damage evolutionary characteristics. [Display omitted] • The cooperative competition evolution mechanism between melt-phase and voids during micro-spallation and recompression is revealed. • The influence of damage history on subsequent deformation and fracture processes is analyzed via MD. • A theoretical framework is proposed for damage description including two models from the view of void and melt-phase evolution, respectively. [ABSTRACT FROM AUTHOR]

• Shock compression of porous Cu with various gas concentrations, porosities and shock intensities is studied via MD. • The HEL of porous metals increases with higher gas concentration and decreases with larger porosity. • The back-and-forth propagation of elastic shockwave leads to the formation of the "surface cap" structure. • The presence of gas significantly inhibits the post-shock temperature rising. • A new model for predicting the Hugoniot of porous materials containing gas is proposed based on Wu-jing EOS. Shock compression of porous copper containing helium is studied via non-equilibrium molecular dynamic simulations. The results show that the shock propagation exhibits an elastic-plastic double-shockwave structure at low shock velocity. The shock Hugoniot elastic limit increases with higher gas concentration, and decreases with larger porosity, while almost independent of the shock velocity. The back-and-forth propagation of elastic shockwave between plastic shockwave and free surface leads to the occurrence of the special structure of "surface cap", which can protect the porous metal in the vicinity of the free surface from collapse. The plastic shock propagates faster with higher gas concentration and gradually catches up with the elastic shockwave as shock intensity increases. Compared with porous copper without gas, the presence of helium significantly inhibits the post-shock temperature rising and the shock melting behavior. A new theoretical model was proposed to quantify the shock Hugoniot of porous materials containing gas. The model's predictions align well with MD simulations across a wide pressure range up to 100 GPa with different gas concentrations and porosities. [ABSTRACT FROM AUTHOR]

• A LiBr-H 2 O concentration difference cold storage system was proposed. • The system performance of hybrid cycles was investigated experimentally. • The energy balance between the subsystems was analyzed. Solar-powered LiBr absorption cooling system is of potential in the application of air-conditioning. A LiBr-H 2 O concentration difference cold storage system driven by vapor compression heat pump was proposed. This cold storage process is not affected by the environmental conditions, since the main energy input is low price electricity at night. The experimental results show that the energy storage density (ESD) can reach 77.8 kWh/m3 and the energy storage coefficient of performance (ESCOP) is 2.81 with low heat loss. The ESCOP means the energy stored in the cold storage process divided by the total electricity consumption in the absorption and heat pump subsystem. The heat transfer in the condenser of the absorption subsystem approximately equals that in the evaporator of the heat pump, and the electricity consumption of the circulating pump in the absorption subsystem is low. Therefore, the value of ESCOP should be slightly lower than the COP of the heat pump system but for higher than 1. These results indicate the feasibility of improving the system efficiency, the operation cost, and long term operation of the solar air conditioning system by coupling the absorption and vapor compression cooling cycles. Finally, the influence of working parameters on the system performance is discussed based on the experimental and simulation analyses. The energy balance between the absorption cycle and the heat pump cycle in the cold storage system is analyzed. It is found that the coefficient of performance of the heat pump (COP ele,HP) and ESCOP increase with a low initial LiBr-H 2 O solution concentration. The ESCOP decreases by 34.4% when the initial concentration increases from 52% to 57%. The average ESD increases to 140.2 kWh/m3 with a concentration difference of 8%. Based on the experiment results, the payback period of the proposed system is estimated as 2.4 years comparing with the traditional LiBr-H 2 O absorption system. [ABSTRACT FROM AUTHOR]

During biomass thermochemical conversion, addition of inert heat carriers such as sand, metal and ceramic balls into the reactor can effectively promote the flow mixing and conduction heat transfer of biomass. Therefore, it is important to understand the flow behavior of the binary mixture containing biomass and heat carrier for efficient utilization of biomass energy. In this study, computational fluid dynamics and discrete element method (CFD-DEM) were used to evaluate the flow behavior and law of the binary mixture of heat carrier and biomass in a novel down-tube pyrolysis reactor. The results show important effects of different ceramic ball sizes and different mass ratios on the flow behavior of binary mixtures. Under the same mass ratio, the smaller the particle size of ceramic balls were, the greater the effect to promote the motion of biomass particles. The fluid-like motion changed more obvious with the increase of mass ratio and biomass particles. [ABSTRACT FROM AUTHOR]

Bentonite is considered as a suitable sealing material for radioactive waste geological repositories because of its high swelling capacity and low permeability. Regardless of the construction procedure and initial form of the bentonite, i.e. blocks, pellets, powder or combinations and mixtures thereof, the placement of the bentonite barrier results in initial heterogeneities which could potentially form preferential pathways for the migration of radionuclides. This study focused on the laboratory investigation of the homogenisation of Czech BCV bentonite. The analysis comprised the performance of four sets of tests on dual-density samples composed of two layers of bentonite compacted to various dry densities. Each set of tests considered two identical samples saturated from different sides under constant volume conditions. Homogenisation was investigated through the measurement of swelling pressure on both sides of the samples and via the determination of the final density distribution in a vertical profile from the post-mortem analysis. The results confirmed a substantial degree of homogenisation, with only a small density gradient revealed by the post-mortem analysis. The density distribution profiles indicated a gradual change in the vertical direction with no distinct border between the original layers. A higher degree of homogenisation was found in the samples with a higher overall density and, consequently, a higher swelling potential. No clear effect of the direction of saturation on homogenisation was identified from the density profiles. The final swelling pressures corresponded well to swelling pressures obtained on single-density samples with density equal to the global density of the dual-density samples. The numerical modelling represented well the final swelling pressures and the swelling pressure evolution curves for both the single- and dual-density samples (including the distinct experimentally-observed swelling pressure peak when the dual-density sample was saturated from the high-density end). More accurate results were obtained while considering the porosity and the degree of saturation-dependent permeability. However, the model did not fully capture the homogenisation of the dual-density samples in terms of the dry density profiles. While the tendency towards homogenisation was predicted correctly, two distinct density zones were evident in the simulations, while the experiment revealed a gradual density distribution. • A good homogenisation potential of bentonite during hydration was detected. • A small residual density gradient was identified via the post-mortem analysis. • No effect of the direction of saturation on the final density profile was found. • A hypoplastic numerical model predicted to a high degree the final swelling pressures. [ABSTRACT FROM AUTHOR]

• A 3 kW silica gel-water adsorption air-conditioner is designed and manufactured. • Cooling power and COP can reach 3.98 kW and 0.632, respectively. • Small hot water flow rate can reduce unmatching between heating and cooling operation of adsorption bed. • Adsorption air-conditioner can be used for cooling and heating cogeneration. • Adsorption air-conditioner is suitable for residential solar cooling application. Compared to adsorption chiller, adsorption air-conditioner can get significant benefit of less cost and complexity when it directly provides chilled air for air-conditioning. Hence, adsorption air-conditioner is suitable for residential solar cooling application. A 3 kW adsorption air-conditioner using silica gel-water working pair is designed and manufactured and its performance is fully tested under different conditions. The experimental results show that cooling power and COP can reach 3.98 kW and 0.632, respectively, without obvious periodic fluctuation of chilled air outlet temperature and relative humidity. Smaller hot water flow rate can help to reduce unmatching between heating and cooling operation of adsorption bed. Optimal half cycle time of this adsorption air-conditioner is found to be 750 s. COP of adsorption air-conditioner is generally larger than that of adsorption chiller which provides chilled water because of higher evaporation temperature. Besides, cooling water outlet temperature can reach 39.9 °C which can meet the requirement of domestic hot water use. So that adsorption air-conditioner can be used for cooling and heating cogeneration in a residential solar cooling application and achieve good performance. [ABSTRACT FROM AUTHOR]

Bentonites are considered to be the most suitable materials for the multibarrier system of high-level radioactive waste repositories. Since BCV bentonite has been proved to be an ideal representative of Czech Ca-Mg bentonites in this respect, it has been included in the Czech Radioactive Waste Repository Authority (SÚRAO) buffer and backfill R&D programme. Detailed knowledge of processes in the material induced by thermal loading provides invaluable assistance regarding the evolution of the material under repository conditions. Samples of both original BCV 2017 bentonite and the same material thermally treated at 200 °C were characterised by means of chemical analysis, powder X-ray diffraction, infrared spectroscopy, thermal analysis, cation exchange capacity, specific surface area (BET) measurements, the determination of the swell index, the liquid limit, the swelling pressure and water retention curves. The smectite in BCV 2017 bentonite comprises Ca-Mg montmorillonite with a significant degree of Fe3+ substitution in the octahedral sheet. Two main transformation processes were observed following heating at 200 °C over 27 months, the first of which comprised the dehydration of the montmorillonite and the subsequent reduction of the 001 basal distance from 14.5 Å (the original BCV 2017) to 9.8 Å, thus indicating the absence of water molecules in the interlayer space. The second concerned the dehydration and partial dehydroxylation of goethite. With the exception of the dehydration of the interlayer space, the PXRD and FTIR study revealed the crystallochemical stability of the montmorillonite in BCV 2017 bentonite under the selected experimental conditions. The geotechnical tests indicated no major changes in the mechanical properties of the thermally treated BCV 2017 bentonite, as demonstrated by the similar swelling pressure values. However, the variation in the swell index and the gradual increase in the liquid limit with the wetting time indicated a lower hydration rate. The retention curves consistently showed the lower retention capacity of the thermally treated samples, thus indicating the incomplete re-hydration of the thermally treated BCV 2017 exposed to air humidity and the difference in its behaviour compared to the material exposed to liquid water. [ABSTRACT FROM AUTHOR]