Changes In Physical Properties Research Articles

Changes in microbial, chemical, physical and techno-functional properties of liquid egg yolk during hyperbaric storage

The effects of hyperbaric storage (HS) at 200 MPa on the microbial, chemical, physical and techno-functional properties of liquid egg yolk were investigated and compared to refrigeration. Inoculated Salmonella enterica (3.35 ± 0.12 logCFU g−1) and Staphylococcus aureus (2.78 ± 0.19 logCFU g−1) resulted below the detection limit after 24 and 48 h HS, respectively. Liquid egg yolk oxidative status remained unaffected for up to 28 days under pressure, probably due to the presence of egg yolk antioxidants. The decrease in egg yolk denaturation enthalpy and the increase in aromatic amino acid exposure indicated that egg yolk proteins unfolded according to structural changes other than those observed during refrigeration. Liquid egg yolk viscosity progressively increased during HS, eventually leading to gelling. Protein modification did not affect liquid egg yolk foaming and emulsifying properties but impaired its solubility and thermally-induced gelling. HS could be used for microbial decontamination of liquid egg yolk while maintaining oxidative stability and the typical capacity to stabilize foams and emulsions.

The effect of different meat types on the in vitro digestibility of starch and protein in meat noodles

The incorporation of meat into noodles and pasta has the potential to enhance their nutritional qualities, flavor, aroma, and taste. This study aimed to investigate the digestibility of three types of meat noodles prepared using chicken breast (CN, CTN) and shrimp meat (SN) as raw materials, and compare them with commercial semolina dried noodles (CON). A simulated static gastrointestinal digestion model was employed and the changes in physical properties, starch digestibility, and protein digestibility during digestion were monitored. The results showed that all meat noodles exhibited prolonged digestion time compared to CON, especially for the formulation containing tomato powder (CTN) showing a higher amount of remaining solids throughout the entire digestion process. CON showed significantly higher free glucose content and lower free amino acids at the end of digestion compared to meat noodles. There were no significant differences in remaining solids and starch digestibility between CN and SN, although SN provided less digestible peptides and exhibited lower elastic modules due to its lower protein content. These findings shed light on the digestibility of meat noodles and offer valuable guidance for the industry in selecting suitable meat sources to produce instant diet options that are high in protein and well-balanced nutritionally.

Development of Interparticle Bonding during Sintering of Metal Powders with the Addition of Carbon

Introduction. Publications on sintered metal powder parts consider interparticle bonding in hot-deformed materials and features of low-alloy structural steels, as well as the use of carbon-containing materials. The authors of the presented article have previously investigated sintering in relation to structural changes in the material, described changes in physical and mechanical properties, reduction of oxides, recrystallization, etc. This paper shows the relationship of mechanical properties of powder steels with the parameters of intracrystalline bonding. The kinetics of its development during sintering is demonstrated for the first time. The study objective is to find out how sintering affects the interparticle bonding and structure of powder alloys with iron and carbon. The task is to study the technological modes of sintering samples from alloyed and pure iron powder to achieve the best mechanical characteristics.Materials and Methods. The powders of the Höganäs company were sintered at a temperature of 900-1150 ºС for 0.5–2.5 hours. The protective gas medium (dissociated ammonia) made it possible to prevent oxidative and other sintering reactions. For static cold pressing, a hydraulic press 2PG-125 with a maximum force of 1250 kN was used.Results. For the first time, the presence of intracrystalline bonding mechanisms with different intensity during sintering has been experimentally established. The dependences of the increment of the relative area of the contact surface on the duration of the isothermal exposure were constructed. With an increase in the sintering temperature to 1150 ºС and a holding time of more than 80 minutes, the contact surface area gradually increased. It was shown that the samples from the powder grades under consideration formed an intracrystalline bonding on the entire contact surface at 1150 ºС. Therefore, this technology can be recommended for practical use. The addition of graphite to the charge slows down the growth of the contact surface. At the same time, the molds from pure powder ABC100.30 and from Distaloy HP-1 powder showed differences. In the first case, with the addition of graphite to the charge, the contact surface developed more intensively than in the second one. The obtained results were recorded in the photo and visualized in the form of graphs.Discussion and Conclusion. According to the results of mechanical tests, it is possible to estimate the proportion of the contact section of the molding with intracrystalline bonding. Its feature is the structural correspondence of the interparticle surface of the splice and the intergrain boundary. The value of this boundary is determined by comparing the relative area of the contact section with the intracrystalline bonding and the relative area of the contact surface. The possibilities of improving the quality of bonding of powder steels by increasing the temperature and time of their exposure during sintering are determined.

Eulerian simulations of local liquid distribution in a Trickle Bed: Effects of flow rates and liquid properties

We performed Eulerian simulations of gas–liquid flow in a Trickle Bed Reactor (TBR) to understand contributions of gas–liquid, gas–solid and liquid–solid interaction forces (F→GL,F→GS,F→LS), capillary-pressure (F→C) and mechanical-dispersion (F→D) forces to local liquid spreading and how their contributions change with changes in flow rates and physical properties. Further, we simulated effects of these parameters on pressure drop (ΔP), overall liquid hold-up (〈εL〉) and importantly on local liquid spreading and validated the predictions using measurements. We have shown that F→LS significantly contributes to local liquid spreading, ΔP and 〈εL〉, whereas F→D contributes marginally. The modified F→LS model led to satisfactory predictions of local liquid spreading, ΔP and 〈εL〉 for a wide range of fluid flow rates and physical properties and predictions are in a satisfactory agreement with the measurements. The present work is an important step in extending the CFD model for simulating reactions and heat effects in TBRs.

Evaluation of UV aging resistance of bitumen containing lignosulfonate grafted layered double hydroxides

The service life of bitumen pavement is impacted by ultraviolet (UV) light and some other conditions, which affected the physical properties and rheological behaviors of bitumen obviously. Lignosulfonate grafted layered double hydroxides modified bitumen (LS-g-LMB) was prepared, and the evaluation of UV aging resistance was investigated through Fourier Transform Infrared Spectroscopy (FTIR), aging indexes, temperature sensitivity, dynamic shear rheometer (DSR) and rheological dynamic model analyzer. The results revealed that lignosulfonate grafted layered double hydroxides (LS-g-LDHs) could alleviate bituminous oxidation reaction, variations of aging indexes and temperature susceptibility in the period of UV exposure observably. After aging, LS-g-LMB showed better low (G', G“ and tanδ) and high temperature (G*, δ and G*/sinδ) performance than pristine bitumen (PB) and layered double hydroxides modified bitumen (LMB). Meanwhile, the instantaneous elasticity, delay elasticity and viscous deformation of bitumen could be inhibited by LS-g-LDHs based on the rheological model analyses. Therefore, the introduction of LS-g-LDHs could promote the UV aging resistance of bitumen significantly according to the changes of bituminous physical properties and rheological behaviors before and after UV aging.

The changes in microstructural features and physical properties of ceramic matrix composite bonding tools under ultrasonic service

Tape automated bonding (TAB) process plays a key role in the production of disk drives, microchips and other microelectronics components. Such tools should sustain their structures and properties throughout ultrasonic operation and are expected to last until reaching the targeted numbers of TAB cycles. This project aims to evaluate the changes in microstructures and physical properties of the bonding tools under ultrasonic service. Three commercial waffle-type tools from different suppliers were focused, namely Tool A, Tool B and Tool C. They provide different levels of bonding efficiency up to 50k cycles under relatively similar ultrasonic practice. Non-destructive and destructive testing methods were examined by the means of X-Ray and mass spectroscopy techniques, respectively. The waffle-end tips of the selected tool were observed using a confocal microscope. The changes in grain size and grain size distribution before and after ultrasonic service were quantitatively analyzed via electron micrographs. Also, their bulk density, hardness and toughness were determined. The experimental work revealed the variation in microstructural features and properties among the three, leading to the difference in ultrasonic efficiency, even they all contained similar phase composition. The relationship between microstructures, properties and ultrasonic efficiency was also reported and discussed.

Susceptibility of winter cut red pine (P. resinosa) stumps to heterobasidion root disease (HRD) infection

Heterobasidion root disease (HRD), a destructive disease of conifers, is a growing management concern. Infection by HRD fungus ( Heterobasidion irregulare) most often occurs when spores, usually produced when temperature is between 5 and 32 °C, land and germinate on freshly cut surfaces. Older stump surfaces are generally unsuitable for colonization, likely due to changes in chemical and physical properties of wood and competitor fungi that limit HRD infection. Stump protectants are effective but not used or recommended in subfreezing temperatures during winter when spores are less common. This study evaluated the potential for older cut stump infection following snowmelt in spring via inoculation of disks collected 7 weeks following initial thinning and exposed to extensive subfreezing temperatures. We found that a surprising number of disks (40%) were successfully colonized with H. irregulare. More research on potential for winter cut conifer HRD infection is warranted as are steps to limit this potential.

Oxidized Xanthan Gum Crosslinked NOCC: Hydrogel System and Their Biological Stability From Oxidation Levels of the Polymer.

Dynamic hydrogel systems from N,O-carboxymethyl chitosan (NOCC) have been investigated in the past years which has facilitated their widespread use in many biomedical engineering applications. However, the influence of the polymer's oxidation levels on the hydrogel biological properties has not been fully investigated. In this study, chitosan was converted into NOCC and introduced to react spontaneously with oxidized xanthan gum (OXG) to form several injectable hydrogels with controlled degradability. Different oxidation levels of xanthan gum, as well as NOCC/OXG volume ratios, were trialed. The infrared spectroscopy spectra verified chemical modification on OXG and successful crosslinking. With increasing oxidation levels, more dialdehyde groups were introduced into the OXG, resulting in changes in physical properties including gelation, swelling, and self-healing efficiency. Under different volume ratios, the hydrogel showed a stable structure and rigidity with higher mechanical properties and a slower degradation rate. The shear-thinning and self-healing properties of the hydrogels were confirmed. In vitro assays with L929 cells showed the biocompatibility of all formulations although the use of a high amount of OXG15 and OXG25 limited the cell proliferation capacity. Findings in this study suggested a suitable amount of OXG at different oxidation levels in NOCC hydrogel systems for tissue engineering applications. This article is protected by copyright. All rights reserved.

Effect of recycled asphalt waste on mechanical properties of alkali-activated mortars

In the next century, negative effects, such as an increase in temperature level, rise in sea level and decrease in forests and agricultural areas, are expected as a result of the harmful effects of global warming. The construction industry is among the main actors of global warming. Cement, the most used building material of the construction industry, is responsible for approximately 8% of CO2 emissions worldwide. Reducing the amount of cement production and using alternative materials and wastes can contribute to reducing CO2 emissions in the production of building materials. In this study, Alkali-Activated Mortar (AAM) mixtures which contain Ground Granulated Blast Furnace Slag (GGBFS) and Fly Ash (FA) were prepared. Recycled Asphalt Waste (RAW) is reduced to 0–4 mm size in order to use as fine aggregate in AAM mixes. Three different activation temperatures (40 °C, 80 °C and 120 °C) were applied for 18 h in order to examine the effect of activation temperature on the prepared AAM samples. After the application of activation temperature, the samples were kept in the standard curing pool for 7 and 28 days. After curing, physical and mechanical experiments were carried out on AAM samples. Water absorption and porosity, compressive strength and electrical resistivity tests were performed on the hardened samples. In addition, the acid effect on the samples was investigated comparatively with the changes in mechanical and physical properties. As a result, the study, in which high-strength mortar mixtures were obtained, shows promising results in terms of sustainable environmentalism. The compressive strength value of 45.74 MPa was found in the mortar mixtures produced using RAW. In addition, it was concluded that the optimum activation temperature is an important parameter of compressive strength and acid resistance.

Microstructure Characteristics and Tribological Properties of Gradient Cu-MoS2 Self-Lubricating Coating Fabricated by Selective Laser Melting of Ink-Printed Metal Nanoparticles

Abstract Self-lubricating coating has been used in industrial applications with severe conditions, such as high temperatures, vacuum, radiation, etc. In this paper, a selective laser melting of ink-printed metal nanoparticles (SLM-IP metal NPs) rapid manufacturing method was applied to fabricate Cu-MoS2 self-lubricating coating. A tailored ink consisting of metal NPs, reductant, and dispersant was deposited on a stainless steel substrate, forming the laminated gradient Cu-MoS2 coating. The microstructure and mechanical properties of the composite coating were characterized. The friction and wear behavior were experimentally investigated by dry sliding wear test at room and higher temperatures (>200 °C). The results indicated that the upper copper sulfur molybdenum compound layer with homogeneously distributed MoS2 provided a significant friction reduction and wear resistance. The SLM-IP Cu-MoS2 coatings showed a reduced friction coefficient by 54% compared to the pure Cu coating. The transitional Cu layer mitigated the abrupt changes in physical properties and enhanced the bonding strength between the coating and substrate. Especially, under the test condition of 200 °C, the Cu-40 vol% MoS2 coating also presented an excellent resistance to oxidation and had a lower friction coefficient of 0.24. This research provides the feasibility of fabricating self-lubricating coatings by the SLM-IP metal NPs method for surface engineering technologies.

Preparation of Self-Coating Al2O3 Bonded SiAlON Porous Ceramics Using Aluminum Dross and Silicon Solid Waste under Ambient Air Atmosphere.

Al2O3-bonded SiAlON ceramic with self-coating was prepared using aluminum dross and silicon solid waste as starting materials under ambient air conditions. The changes in phase, microstructure, and physical properties of the ceramic with temperature were analyzed and the formation mechanism of the SiAlON phase was elucidated. The results showed that higher temperature was more suitable for the preparation of SiAlON ceramics. As the temperature increased from 1400 to 1600 °C, the main phases in the ceramic transformed from mullite, Al2O3, and SiAlON to Al2O3 and SiAlON. An Al2O3-rich layer spontaneously coated the surface of the porous ceramic as Al melted and oxidized at high temperature. The thickness of this layer decreased as the temperature increased. The presence of Al2O3-rich coating layer impeded air flow, allowing nitriding of Si and Al, and the formation of the SiAlON phase in ambient air conditions. This study not only presents a strategy to successfully recycle aluminum dross and silicon solid waste but also offers a straightforward approach to preparing SiAlON material in air atmosphere.

Structural insight into the cooperativity of spin crossover compounds.

Spin-crossover (SCO) compounds are promising materials for a wide variety of industrial applications. However, the fundamental understanding of their nature of transition and its effect on the physical properties are still being fervently explored; the microscopic knowledge of their transition is essential for tailoring their properties. Here an attempt is made to correlate the changes in macroscopic physical properties with microscopic structural changes in the orthorhombic and monoclinic polymorphs of the SCO compound Fe(PM-Bia)2(NCS)2 (PM = N-2'-pyridylmethylene and Bia = 4-aminobiphenyl) by employing single-crystal X-ray diffraction, magnetization and DSC measurements. The dependence of macroscopic properties on cooperativity, highlighting the role of hydrogen bonding, π-π and van der Waals interactions is discussed. Values of entropy, enthalpy and cooperativity are calculated numerically based on the Slichter-Drickamer model. The particle size dependence of the magnetic properties is probed along with the thermal exchange and the kinetic behavior of the two polymorphs based on the dependence of magnetization on temperature scan rate and a theoretical model is proposed for the calculation of the non-equilibrium spin-phase fraction. Also a scan-rate-dependent two-step behavior observed for the orthorhombic polymorph, which is absent for the monoclinic polymorph, is reported. Moreover, it is found that the radiation dose from synchrotron radiation affects the spin-crossover process and shifts the transition region to lower temperatures, implying that the spin crossover can be tuned with radiation damage.

The Effects of Thermocycling on the Physical Properties and Biocompatibilities of Various CAD/CAM Restorative Materials.

The purpose of this study is to evaluate the changes in physical properties and biocompatibilities caused by thermocycling of CAD/CAM restorative materials (lithium disilicate, zirconia reinforced lithium silicate, polymer-infiltrated ceramic network, resin nanoceramic, highly translucent zirconia). A total of 225 specimens were prepared (12.0 × 10.0 × 1.5 mm) and divided into three groups subjected to water storage at 37 °C for 24 h (control group), 10,000 cycles in distilled water at 5-55 °C (first aged group), and 22,000 cycles in distilled water at 5-55 °C (second aged group) [(n= 15, each]). The nanoindentation hardness and Young's modulus (nanoindenter), surface roughness (atomic force microscopy (AFM)), surface texture (scanning electron microscopy (FE-SEM)), elemental concentration (energy dispersive spectroscopy (EDS)) and contact angle were evaluated. The morphology, proliferation and adhesion of cultured human gingival fibroblasts (HGFs) were analyzed. The data were analyzed using one-way ANOVA and Tukey's test (p < 0.05). The results showed that the nanoindentation hardness and Young's modulus were decreased after thermocycling aging. Cell viability and proliferation of the material decreased with aging except for the highly translucent zirconia. Zirconia-reinforced lithium silicate exhibited significantly lower cell viability compared to other materials. The surface roughnesses of all groups increased with aging. Cell viability and Cell adhesion were influenced by various factors, including the surface chemical composition, hydrophilicity, surface roughness, and topography.

The Influence of Mechanical, Physical and Chemical Influences on Protective Clothing

The article is focused on testing the mechanical, physical and chemical characteristics of the selected protective clothing. Old anti-chemical protective clothing formerly used in tactical exercises (but never during a real intervention) was selected. Protective clothing has an expected lifespan when used correctly. When in use, external influences can negatively affect and function of these garments. The article describes the preparation of individual samples of protective clothing which were exposed to the effects of selected inorganic and organic chemicals, water vapor, UV radiation and long-term exposure to elevated temperatures. The prepared samples were subsequently torn on the tearing device, and the change of mechanical and physical properties was monitored. The stress at which the samples broke and the length they reached at the moment of breaking were measured. The exposure to individual chemicals, UV radiation and elevated temperature resulted in decreases in the modulus of elasticity in each case. The largest decrease was recorded in samples treated with hydrogen peroxide and the smallest in samples exposed to long-term thermal load.

Structurally decoupled stiffness and solute transport in multi-arm poly(ethylene glycol) hydrogels

Synthetic hydrogels are widely used as artificial 3D environments for cell culture, facilitating the controlled study of cell-environment interactions. However, most hydrogels are limited in their ability to represent the physical properties of biological tissues because stiffness and solute transport properties in hydrogels are closely correlated. Resultingly, experimental investigations of cell-environment interactions in hydrogels are confounded by simultaneous changes in multiple physical properties. Here, we overcame this limitation by simultaneously manipulating four structural parameters to synthesize a library of multi-arm poly (ethylene glycol) (PEG) hydrogel formulations with robustly decoupled stiffness and solute transport. This structural design approach avoids chemical alterations or additions to the network that might have unanticipated effects on encapsulated cells. An algorithm created to statistically evaluate stiffness-transport decoupling within the dataset identified 46 of the 73 synthesized formulations as robustly decoupled. We show that the swollen polymer network model accurately predicts 11 out of 12 structure-property relationships, suggesting that this approach to decoupling stiffness and solute transport in hydrogels is fundamentally validated and potentially broadly applicable. Furthermore, the unprecedented control of hydrogel network structure provided by multi-arm PEG hydrogels confirmed several fundamental modeling assumptions. This study enables nuanced hydrogel design for uncompromised investigation of cell-environment interactions.

The delaying effect of a novel polyethylene nanopackaging on postharvest stipe elongation of Flammulina velutipes and its mechanism analysis

The stipe elongation is a typical characteristic of quality deterioration of postharvest Flammulina velutipes. We explored the delaying effect of a novel polyethylene nanopackaging (PENP) on stipe elongation in F. velutipes during storage and the underlying mechanism. The changes in quality, physical and chemical properties, and gene expression of F. velutipes in PENP during 18-day storage at low temperature were analyzed by morphological observation and physiological, biochemical, and transcriptomic methods. The results showed that PENP treatment could reduce the respiration of F. velutipes by maintaining higher CO2 and lower O2 content, decrease the stipe elongation rate and keep the postharvest storage quality of F. velutipes. PENP also inhibited the increase in chitin and β-glucan content, the main components of the cell wall of F. velutipes, maintaining sufficient ATP content and energy charge (EC) values inside the stipe. Transcriptome analysis showed that PENP inhibited cell wall regeneration by down-regulating genes related to chitin degradation (Unigene0001917, Unigene0018811 and Unigene0007053) and β-glucan degradation (Unigene0010562 and Unigene0010561), thus delaying stipe elongation. During the early stage of storage, PENP also inhibited energy metabolism by down-regulating succinate dehydrogenase (SDH), cytochrome c oxidase (CCO), and F1F0-ATPase-related genes involved in the oxidative phosphorylation pathway. In summary, PENP delayed postharvest stipe elongation of F. velutipes by inhibiting the synthesis of chitin and glucan in the cell wall and maintaining low energy metabolism in the stipe cells during early storage.

Mass Transfer Analysis of CO2-Water-Rock Geochemical Reactions in Reservoirs

It is difficult to exploit low-permeability reservoirs, and CO2 flooding is an effective method to improve oil recovery from low permeability reservoirs. However, in the process of CO2 flooding, acidic fluids dissolved in formation water will react with rock to cause dissolution and precipitation, resulting in pores and precipitates, changing the evolution law of seepage channels, destroying formation integrity, and affecting the effect of CO2 oil displacement. The change in rock’s physical properties and the mass transfer law between CO2-water-rock are unclear. This paper considers the coupling effects of seepage, mechanics, and chemistry when CO2 is injected into the formation. The mass transfer model of CO2-water-rock in the geochemical reaction process is established on this basis. The physical properties of the reservoir after CO2 injection are quantitatively studied based on the microscopic mechanism of chemical reaction, and the migration law of solute in the reservoir rock during CO2 flooding under the coupling effects of multiple fields is clarified. The experimental results show that with the increase in reaction time, the initial dissolution reaction of formation rocks will be transformed into a precipitation reaction of calcite, magnesite, and clay minerals. The porosity and permeability of the rocks near the well first increase and then decrease. The far well end is still dominated by dissolution reactions, and the average values of formation porosity and permeability show an upward trend. Although the dissolution reaction of CO2-water-rock can improve the physical properties of reservoir rocks to a certain extent, the mutual transformation of the dissolution reaction and precipitation reaction further exacerbates the heterogeneity of formation pore structure, leading to the instability of CO2 migration, uneven displacement, and destruction of formation stability. The research results of this paper solve the problem of quantitative calculation of physical parameters under the coupling effect of multiple fields after CO2 injection into reservoirs and can predict the changes in formation physical properties, which can provide a certain theoretical basis for evaluating formation integrity and adjusting CO2 injection under the condition of CO2 flooding.

Influence of ferrochrome slag as coarse and fine aggregates on thermal and strength properties of concrete at high temperatures

Ferrochrome slag (FCS) as aggregates in concrete provides a sustainable alternative for the construction industry due to its admirable mechanical, durability, and refractory properties. These characteristics of FCS may aid in increasing the strength and durability aspects of the concrete. However, when subjected to high temperatures, the characteristics of concrete incorporating FCS aggregates are not well understood. Therefore, the study examined the effects of replacing natural coarse and fine aggregates with FCS aggregates on the thermal and strength properties of concrete, as well as the resistance of FCS concrete to high temperatures. Along with the reference conventional concrete mixture, four other concrete mixtures were produced using FCS fine and coarse aggregates at replacement percentages of 25%, 50%, 75% and 100% of natural stone aggregates. The residual mechanical properties, mass loss, ultrasonic pulse velocity, and change in different physical properties of the concrete mixtures were tested before and after experience to high temperatures between 200 °C and 1000 °C. The experimental data is also used to derive the relationship between temperature and strength reduction factors for FCS concrete. The inclusion of FCS aggregates was found to maintain relatively higher mechanical properties and less mass loss in the concrete after heat treatment. The thermal characteristics of FCS play an important role in enhancing the high-temperature performance of concrete with FCS aggregates.

Dynamics of physical properties of soils and humus reserves in salted soils under desertification

The dynamics of the physical properties and reserves of humus in saline soils of an arid semi-desert zone is presented. The basis for the research was observational data for 2010-2022. in a typical hilly landscape of the Astrakhan region. A grid of 100 × 100 m was laid. Soil studies were carried out at the grid nodes along the sampling layers. We studied the change in physical properties (soil moisture; salt content according to the amount of dense residue; soil density; filtration coefficient; soil porosity; moisture reserve), humus reserves and salt state of saline soils under desertification. Comparative analysis showed that negative changes have taken place in the study area and it can be stated that the processes of soil degradation and desertification are intensively developing. It has been established that in the soil layer of 0–40 cm there was a significant reduction in soil moisture reserves against the background of an increase in maximum air and soil surface temperatures, as well as changes in the hydrological regime because of the embankment of the territory. Dehumification processes are observed. The most clearly negative trend was revealed for meadow solonchaks. The change in the hydrological regime of the territory because of embankment contributes to an increase in the areas of automorphic soils in the landscape and a reduction in the areas of meadow soils. An increase in the degree of salinity and compaction was recorded for automorphic zonal soils. The physical destruction of the Baer's hills exacerbates the processes of degradation and the development of desertification in such conditions.

Thermo-hydro-mechanical coupling simulation for fracture propagation in CO2 fracturing based on phase-field model

CO2 fracturing is extensive used in unconventional oil and gas reservoir, geothermal resources, metal uranium mining, and CO2 geological storage. At present, the fluid-solid coupling model for fracture propagation with CO2 does not consider the influence of heat exchange between CO2 fracturing fluid and the formation, which leads to the deviation between the simulation results and field. Based on the phase-field models, considering the thermal stress and CO2 physical properties change induce by thermal effect, a Thermo-hydro-mechanical coupling model is established for CO2 fracturing. This paper studies the influence of formation horizontal stress difference, approaching angle and fracturing fluid injection temperature. The results indicate that, compared with hydraulic fracturing, CO2 fracturing can significantly reduce the fracture initiation pressure and time, and obtain a more complex fracture morphology with the same stress difference. For natural fractures, the approaching angle is linearly related to the initiation pressure and initiation time of opening new fractures. With the growth of approaching angle, the initiation pressure and initiation time increase respectively. The fracture shows increase in fracture morphology complexity induced by a stronger thermal stress with the growth of temperature differences. CO2 fracturing simulation thermal stress should be considered for a precision of fracture morphology.