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Thermal boundary conditions of the turbine disk cavity system are of great importance in the design of secondary air systems in aero-engines. This study aims to investigate the complex heat transfer mechanisms of a rotating turbine disk under high-speed conditions. A high-speed rotating free-disk model with Dorfman empirical solutions is developed to evaluate the heat transfer performance considering various factors. Specifically, the influence of compressibility, variable properties, and heat dissipation is determined using theoretical and numerical analyses. In particular, a novel combined solution method is proposed to simplify the complex heat transfer problem. The results indicate that the heat transfer performance of a free disk is primarily influenced by the rotating Mach number, rotating Reynolds number, Rossby number, and wall temperature ratio. The heat transfer temperature and Nusselt number of the free disk are strongly correlated with the rotating Mach number and rotating Reynolds number. Analysis reveals that heat dissipation is a critical factor affecting the accurate evaluation of the heat transfer performance of the turbine disk. Thus, the combined solution method can serve as a reference for future investigations of flow and heat transfer in high-speed rotating turbine disk cavity systems in aero-engines.

The permeability of coal reservoirs in China is generally low, and the benefit of direct development of surface coalbed methane in low permeability reservoirs is low, and hydraulic fracturing is an effective means to increase the permeability and conductivity of coal reservoirs. Based on the analysis of logging parameters of well PN-1 and well PN-2 in Qinshui Basin, the rock mechanics characteristics of coal reservoir are mastered, which provides guidance for the optimization of hydraulic fracturing parameters of coal reservoir. The results show that the coal seam derived from the logging data of the two wells has the characteristics of low Poisson’s ratio, low Young’s modulus, low strength and low rupture pressure. By controlling the construction displacement and pressure and increasing the liquid volume in the pre-liquid phase, the fracturing fracture can be effectively prevented from extending along the interlayer interface between the top and bottom of the coal seam and extending to the top and bottom of the coal seam. The fracture pressure of coal seam in well PN-1 obtained from logging data is close to the actual fracturing pressure, and the error is only 3.01%, which has a high guiding significance for the optimization of fracturing construction parameters. The fracturing pressure of the coal seam in well PN-2 is slightly lower than that of the top and bottom rock, and the construction displacement in the initial stage of fracturing is high, resulting in the construction pressure reaching the fracturing pressure of the top and bottom, and the fracturing fracture extends between the top and bottom to form a single fracture, resulting in poor transformation effect and gas production effect.

Abstract This study comprehensively explores the compaction and compressibility characteristics of snail shell ash (SSA) and ground-granulated blast-furnace slag (GBFS) in stabilizing local bentonite for landfill baseliner applications. The untreated soil, with a liquid limit of 65%, plastic limit of 35%, and plasticity index of 30%, exhibited optimal compaction at a moisture content of 32% and a maximum dry density of 1423 kg/m3. SSA revealed a dominant presence of 91.551 wt% CaO, while GBFS contained substantial 53.023 wt% SiO2. Treated samples with 20% GBFS and 5% SSA exhibited the highest maximum dry density (1561 kg/m3) and optimal moisture content (13%), surpassing other mixtures. The 15% SSA-treated sample demonstrated superior strength enhancement, reaching an unconfined compressive strength of 272.61 kPa over 28 days, while the 10% GBFS-treated sample achieved 229.95 kPa. The combination of 15% SSA exhibited the highest shear strength (49 kPa) and elastic modulus (142 MPa), showcasing robust mechanical properties. Additionally, the 15% SSA sample displayed favourable hydraulic conductivity (5.57 × 10–8 cm/s), outperforming other mixtures. Notably, the permeability test, a critical aspect of the study, was meticulously conducted in triplicate, ensuring the reliability and reproducibility of the reported hydraulic conductivity values. Treated samples with SSA and GBFS showed reduced compressibility compared to the control soil, with the 15% SSA-treated sample exhibiting a more consistent response to applied pressures. Scanning Electron Microscopy analysis revealed substantial composition changes in the 15% SSA mixture, suggesting its potential as an effective base liner in landfill systems. In conclusion, the 15% SSA sample demonstrated superior mechanical properties and hydraulic conductivity, presenting a promising choice for landfill liner applications.

The response of soft colloids to crowding depends sensitively on the particles' compressibility. Nanogel suspensions provide model systems that are often studied to better understand the properties of soft materials and complex fluids from the formation of colloidal crystals to the flow of viruses, blood, or platelet cells in the body. Large spherical nanogels, when embedded in a matrix of smaller nanogels, have the unique ability to spontaneously deswell to match their size to that of the nanogel composing the matrix. In contrast to hard colloids, this self-healing mechanism allows for crystal formation without giving rise to point defects or dislocations. Here, we show that anisotropic ellipsoidal nanogels adapt both their size and their shape depending on the nature of the particles composing the matrix in which they are embedded. Using small-angle neutron scattering with contrast variation, we show that ellipsoidal nanogels become spherical when embedded in a matrix of spherical nanogels. In contrast, the anisotropy of the ellipsoid is enhanced when they are embedded in a matrix of anisotropic nanogels. Our experimental data are supported by Monte Carlo simulations that reproduce the trend of decreasing aspect ratio of ellipsoidal nanogels with increasing crowding by a matrix of spherical nanogels. [ABSTRACT FROM AUTHOR]

This work describes a derivation of the random contact equation that predicts the packing fraction ϕMRJ hr of a dense disordered (maximally random) jammed state of hard, very elongate particles. This derivation is based on (i) the compressibility equation connecting the compressibility of a uniform system with its pair-correlation function: it is assumed equal to zero at jamming; (ii) the pair-correlation function of the interparticle distance scaled with respect to the orientationally dependent contact distance: it is assumed equal to the sum of a delta function and a unit-step function at jamming, where the former function accounts for the interparticle contacts, while the latter function accounts for the background. On assuming that the hard, very elongate particles are cylindrically symmetric with a length L and a diameter D and isostaticity occurs at jamming, the prediction, in particular that, in the limit of L/D → +∞, ϕMRJ hrL/D = (10 + 1)/2, is compared to the available experimental data. [ABSTRACT FROM AUTHOR]

Richtmyer-Meshkov (RM) instability at a single-mode interface impacted by a cylindrical divergent shock with low to moderate Mach numbers is investigated experimentally. The motion of an unperturbed interface is first examined to obtain the background flow. The shocked interface moves uniformly at the early stage, but later decelerates. The stronger the incident shock, the larger the interface deceleration, which is reasonably predicted by a one-dimensional model considering the effect of postshock non-uniformity. Such a deceleration greatly inhibits the growths of harmonics of an initially perturbed interface and, consequently, the divergent RMinstability presents very weak nonlinearity from early to late stages. Particularly, higher-Mach-number cases present weaker nonlinearity due to larger deceleration there. This abnormal linear growth regime is reported for the first time. Benefiting from this, the incompressible linear model holds validity at all stages of divergent RM instability. It is also found that compressibility inhibits the initial growth rate, but produces a weak influence on the subsequent instability growth. [ABSTRACT FROM AUTHOR]

The water retention curve (WRC) of municipal solid waste (MSW) is the important hydraulic parameter for the study of unsaturated seepage analysis in landfills. Due to the compressibility and degradability of the waste, the search for a method to quickly and accurately test its water retention curve (WRC) is a current problem that needs to be solved. In this paper, considering the volume change of the waste specimens in test, the test principle of centrifuge testing of WRC is corrected to make it applicable to the testing of waste WRC. In addition, the WRCs of 20 MSW specimens with typical landfill compositions and porosities are measured using the corrected centrifuge test. The effects of compositions and porosities of waste specimens on WRC parameters were analyzed. The results are summarized as follows. Disregarding the height reduction of specimens resulted in overestimated matric suction values and underestimating volume water content values. By comparing uncorrected and corrected values, the maximum difference of the matric suction and volumetric water content reach 233 kPa and 11%, respectively. This study can provide a reference for accurately measuring the WRC of MSW using a centrifuge. For the waste specimen without kitchen and yard waste, composition had less of an effect on the WRC of waste compared to porosity. The effect of the content of the non-absorbable fraction on the residual volumetric water content θr and the parameter nv in the van Genuchten model was significant. The initial porosity n had a great effect on the parameter α. [ABSTRACT FROM AUTHOR]

The density (d), ultrasonic velocity (U), and viscosity (η) have been measured for the electrolytes, i.e., potassium chromate, sodium chromate, and sodium thiosulphate in an aqueous solution of dimethyl sulphoxide (DMSO) solution at 293 K, 298 K, 303 K, 308 K, and 313 K. By using the measured data, the other parameters like adiabatic compressibility (β), relative change in adiabatic compressibility (Δβ/β),change in adiabatic compressibility (Δβ),apparent molal volume (Øv), apparent molal compressibility (Øk),intermolecular free length (Lr), specific acoustic impedance (Z), limiting apparent molal compressibility ( ∅ k 0 ), limiting apparent molkal volume (Øv0) and their constants (Sk, Sv) can be calculated. The results obtained from the above parameters are helpful to determine the solute–solute and solute–solvent interaction. [ABSTRACT FROM AUTHOR]

The impact of climate change has become increasingly severe in forests, where droughts and strong winds on the one hand and extreme rainfall events on the other hand can damage forest ecosystems. To mitigate the effects of drought and enhance soil water retention capacity, three types of soil conditioners (SCs), labeled SC_R, SC_CG, and SC_ZZC, were developed as part of the European project ONEforest. All the conditioners are based on Xanthan gum and have different types and amounts of fillers with diverse cellulose fiber lengths. These can offer the potential to optimize the SC characteristics, e.g., water absorption, water retention, and mechanical stability. This paper focuses on the influence of fillers in the SCs on the geotechnical properties of forest soils from Ljubelj in the Alpine part of Slovenia (S1), Catalonia, northeastern Spain (S2), and Heldburg, Germany (S3). The results show an increase of 53% to 100% in the water absorption of treated soil. A less favorable impact of the SCs was found on the drained shear strength and the compressibility. The drained shear strength of untreated forest soils in a saturated state was S1 c′ = 4.4 kPa, φ′ = 33.5°; S2 c′ = 1.4 kPa, φ′ = 30.0°; and S3 c′ = 12 kPa, φ′ = 28.0°. The addition of SCs results in a reduction in the drained shear strength of saturated mixtures. The reduction depends on the dosage of added SC—whether it is a low (L) or a high (H) dosage. For instance, when the soil S1 was treated with a low dosage of the soil conditioner SC_R, it demonstrated a cohesion (c′) of 11 kPa and a friction angle (φ′) of 27.0°. However, increasing the dosage of the SC_R led to a decrease in both the cohesion and the friction angle for the same soil (c′ = 7.7 kPa, φ′ = 25.0°). Additionally, the type of soil conditioner also impacts the drained shear strength. Among the mixtures with a high dosage of the SC_R, SC_CG, or SC_ZZC, those containing the SC_CG with the longest fibers stand out, demonstrating the highest friction angle. Therefore, longer fibers can be a promising component of the SCs to reduce the negative influence of XG on the mechanical properties of treated soils. [ABSTRACT FROM AUTHOR]

The compressibility of composite materials prepared by impregnation with an aqueous polyurethane dispersion of cloth made of polypropylene fibers of linear density 0.66 tex was studied. An approach to the determination of the dependence of the compressibility of the composite materials on the degree of impregnation of the cloth and the pressure on the materials was proposed. The optimal degree of impregnation of the cloth above which a substantial drop of the compressibility was observed was established. The compressibility decreased if bridges of polyurethane particles formed between the fibers. The orientation of the cloth fibers, which depended on the linear density of the fibers during punching of the fabric, was another structural factor determining the compressibility of the composite materials. [ABSTRACT FROM AUTHOR]

Flexible pressure sensors have drawn considerable attention for their potential applications as electronic skins with both sensitivity and pressure response range. Although the introduction of surface microstructures effectively enhances sensitivity, the confined volume of their compressible structures results in a limited pressure response range. To address this issue, a biomimetic kapok structure is proposed and implemented for constructing the dielectric layer of flexible capacitive pressure sensors employing 3D printing technology. The structure is designed with easily deformable concave and rotational structures, enabling continuous deformation under pressure. This design results in a significant expansion of the pressure response range and improvement in sensitivity. Further, the study purposively analyses crucial parameters of the devised structure that affect its compressibility and stability. These include the concave angle θ, height ratio d1/d2, rotation angle α, and width k. As a result, the ultimate pressure sensors demonstrate remarkable features such as high sensitivity (≈2.38 kPa−1 in the range of 0–10 kPa), broad detection range (734 kPa), fast response time (23 ms), and outstanding pressure resolution (0.4% at 500 kPa). This study confirms the viability of bionic structures for flexible sensors, and their potential to expand the scope of wearable electronic devices. [ABSTRACT FROM AUTHOR]

Unicellular organisms such as yeast can survive in very different environments, thanks to a polysaccharide wall that reinforces their extracellular membrane. This wall is not a static structure, as it is expected to be dynamically remodeled according to growth stage, division cycle, environmental osmotic pressure and ageing. It is therefore of great interest to study the mechanics of these organisms, but they are more difficult to study than other mammalian cells, in particular because of their small size (radius of a few microns) and their lack of an adhesion machinery. Using flat cantilevers, we perform compression experiments on single yeast cells (S. cerevisiae) on poly-L-lysine-coated grooved glass plates, in the limit of small deformation using an atomic force microscope (AFM). Thanks to a careful decomposition of force–displacement curves, we extract local scaling exponents that highlight the non-stationary characteristic of the yeast behavior upon compression. Our multi-scale nonlinear analysis of the AFM force-displacement curves provides evidence for non-stationary scaling laws. We propose to model these phenomena based on a two-component elastic system, where each layer follows a different scaling law.. [ABSTRACT FROM AUTHOR]

The feasibility of use of natural nanomaterials, namely, natural aluminosilicate (halloysite) nanotubes and nanocellulose, as modifying additives to commercial polyurethane foam to vary fire resistance and mechanical properties was studied. Series of composite polyurethane foams containing various weight proportions of the modifying additives were obtained via in situ polymerization. The effect of the additives on the polyurethane foam structure, compressibility, and fire resistance was studied. It was observed that introduction of additives into polyurethane foam leads to change of the average pore size and reduction of foams compressibility. However, once the the maximum rigidity of the foam composites was reached, further increase of additive content causes regression of this characteristic. It was also confirmed that increasing additive content positively affects the fire resistance of the produced composites. [ABSTRACT FROM AUTHOR]

Porous rocks exhibit mechanical behaviors characterized by high compressibility and stiffness enhancement under quasi-static cyclic loads. In this study, we investigated the mechanical responses of a porous red sandstone subjected to different cyclic loads and revealed the mesoscopic mechanisms for the evolution of stiffness and strength. Rock stiffness was enhanced by increasing stress and number of load cycles during pre-peak loading, and the normalized viscoelastic strain evolved uniformly during all the unloading phases. Void compaction and microfracturing caused irreversible structural changes and subsequent changes in the stiffness of the rock, and there was a positive linear relationship between the unloading secant modulus and axial irreversible strain. In addition, a new parameter, named the plastic strain increment ratio, was defined to describe the asynchronous development of the axial and lateral irreversible deformation induced by void compaction and microfracturing. These results can provide a better understanding of the mechanical properties of porous sandstone. Highlights: Low-frequency cyclic loads cause stiffness enhancement on the porous red sandstone. Unloading recovery of viscoelastic strain follows a uniform exponential law regardless of loading conditions. The evolution of stiffness is linearly related to the accumulation of irreversible strains. The evolution of stiffness is caused by void compaction and microfracturing. [ABSTRACT FROM AUTHOR]

The uniqueness of entropy solution for the compressible Euler equations is a fundamental and challenging problem. In this paper, the uniqueness of a composite wave of shock and rarefaction of one-dimensional compressible Euler equations is proved in the inviscid limit of compressible Navier--Stokes equations. Moreover, the relative entropy around the original Riemann solution consisting of shock and rarefaction under the large perturbation is shown to be uniformly bounded by the framework developed in [M. J. Kang and A. F. Vasseur, Invent. Math., 224 (2021), pp. 55--146]. The proof contains two new ingredients: (1) a cut-off technique and the expanding property of rarefaction are used to overcome the errors generated by the viscosity related to inviscid rarefaction; (2) the error terms concerning the interactions between shock and rarefaction are controlled by the compressibility of shock, the decay of derivative of rarefaction, and the separation of shock and rarefaction as time increases. [ABSTRACT FROM AUTHOR]

Fiber-reinforced elastomeric isolators (FREIs) have been proposed as a cost-effective solution for expanding the use of seismic isolation to normal-importance structures. By using lightweight fiber reinforcement and eliminating the attachment plates, FREIs reduce cost while improving the isolation efficiency and reducing tensile stresses in the rubber. However, the flexural flexibility of the fiber allows cross-sectional distortions (i.e., warping) to occur, which significantly impacts the stability of these devices. This paper evaluates the buckling of rectangular, circular, and annular FREIs, taking into account shear warping effects. A planar buckling theory previously proposed by the authors is adapted for the three-dimensional problem, and effective warping rigidities and warping-related areas are derived for the above bearing geometries, accounting for rubber compressibility. To assess the adequacy of the proposed buckling theory and derived warping properties in predicting the buckling of FREIs, a parametric finite element study is conducted. The critical load predictions of the proposed analytical formulation are found to be in excellent agreement with those of the numerical simulations. It is shown that traditional estimations of the buckling load that neglect warping are significantly unconservative. Finally, design recommendations and resources are provided for practice-oriented applications. [ABSTRACT FROM AUTHOR]

Experimental and numerical studies on the evolution of shock-accelerated SF6/air interface with small initial amplitude are conducted. The effect of compressibility on the early development of perturbation is highlighted by varying shock intensity and fluid properties. The startup process is analyzed when rarefaction waves are reflected and the characteristic time of the startup process is provided. The relationship between the phase inversion process and the startup process under different incident shock strengths is clarified. According to the startup time, a new start point for normalization is given, which can better normalize the amplitude growth at the early stage. In addition, the effects of incident shock strength and physical properties of fluids on the linear growth rate are highlighted through numerical simulations. The incompressible linear model loses validity when the incident shock is strong, and the existing rotational model is verified to provide excellent predictions under any shock strengths. The decrease in adiabatic exponent of the heavy fluid or the increase in adiabatic exponent of the light fluid can reduce the linear growth rate. As the absolute value of Atwood number increases, the adiabatic exponent of the heavy fluid has a more significant effect on the linear growth than that of the light fluid. [ABSTRACT FROM AUTHOR]

The greatest challenge when performing large deformation simulations using the CFD‐DEM coupling method lies in the dynamical update of the fluid meshes. To address this problem, a novel CFD‐DEM coupling method integrated with the dynamic unstructured grid is proposed in this work. The mesh initialization and reconstruction are performed by the Constrained Delaunay triangulation (CDT) implemented by the tetgen algorithm. Moreover, the equation of state (EOS) is introduced to consider the impact of fluid compressibility. The reliability of this coupling method is preliminarily verified by the particle sedimentation test. Additionally, undrained triaxial shear and one‐dimensional consolidation tests are conducted to examine the applicability of the proposed method in simulating geotechnical cases. From our analysis, it is found that the shear responses in the undrained triaxial shear test obtained from the proposed method with dynamic mesh are in direct accordance with those led by the constant volume (CV) method. However, difficulties arise in accurately describing the moving boundary by the fixed mesh, leading to unreliable results. Moreover, in the one‐dimensional consolidation test, both the dynamic and fixed grids can capture the Mandel—Cryer effect, which is more pronounced under the dynamic grid, mainly due to the dual impact of the loading device and particle skeleton on the fluid. A greater compressibility specified under the dynamic grid led to a weakening of this effect, whereas its duration is increased. Our work provides valuable insights for effectively dealing with dynamic fluid boundaries. [ABSTRACT FROM AUTHOR]

During the tunneling process of earth pressure balance (EPB) shield machines, the undrained compressibility of foam-conditioned soils in the excavation chamber is essential for reducing the fluctuation of chamber pressure and guaranteeing effective tunnel face support. As conditioned soil is simplified to be radially constrained by the shield shell and in a quasi-one-dimensional compression state under the face pressure along the tunneling direction, a mechanism-inspired analytical model was developed to estimate the void ratio and pore pressure of foam-conditioned coarse-grained soils (FCS) in one-dimensional compression based on effective stress analysis. In the model, an expansion coefficient was proposed to characterize the filling state of foam bubbles in pores and a void ratio threshold (eth) was defined as the transition point of the FCS with and without effective stress. The variation of void ratio and pore pressure with total stress of FCS in two distinct stages of the void ratio (e), either greater or smaller than its threshold, were calculated based on Boyle's law and the hyperbolic assumption of the effective stress–strain relation of soil. A good agreement between the analytical and experimental results verified the reliability of the proposed analytical method. Furthermore, a parametric study indicated that the compressibility increases with an increase in the expansion coefficient and foam injection ratio (FIR). Increasing additional water content leads to a decrease in compressibility under low pressure (σv ≤ 20 kPa), but an increase in compressibility under high pressure (σv > 20 kPa). Meanwhile, the pore pressure in FCS in the stage of e < eth also positively correlates with the expansion coefficient, FIR, and additional water content. The research findings would provide a convenient method to estimate the undrained compressibility behavior of FCS and theoretically guide the soil conditioning optimization in EPB tunneling. [ABSTRACT FROM AUTHOR]

Pavements and light structures constructed on expansive subgrade layers have experienced severe damage due to volume changes. These layers have been exposed to climatic changes such as freeze–thaw (FT) cycles. Accurate estimation of design parameters regarding heave/settlement is essential for sustainable performance. This work study the instantaneous and long-term effects of successive FT-cycles on the volume stability, swelling, and compressibility characteristics of natural and lime-treated expansive subgrades. Volume changes were traced during successive 15FT cycles. Swelling and consolidation characteristics were studied immediately after FT-cycles. The long-term effect of FT was tested at different recovery periods around year. FT-cycles significantly affects volume changes and compressibility, this effect is proportional to soil type and limited up to a certain number of FT-cycles. During the long-term recovery, a considerable part of underwent deformation is a permanent and not recovered, even after year the soil still memorizes this effect. Due to the propagated cracks, the plastic deformation increased with increase in FT-cycles. [ABSTRACT FROM AUTHOR]

We construct time almost-periodic solutions (global in time) with finite regularity to the incompressible Euler equations on the torus Td, with d = 3 and d ∈ N even. [ABSTRACT FROM AUTHOR]

This study aims to investigate the compressive and microstructural properties of loess before and after treatment with a new permeable polymer. To enhance the compressive properties of loess, specimens were infused with the new polymer, and one-dimensional consolidation tests were performed to assess the compressibility of solidified loess (SL) and unsolidified loess (UL) at different water contents. Additionally, the microstructure and pore morphology of UL and SL were examined using a scanning electron microscope (SEM) and the Particles (Pores) and Cracks Analysis System (PCAS). Statistical methods were employed to analyze the relationships between microstructural parameters and compression modulus. The experimental results demonstrate a significant improvement in the compressibility of loess when treated with the polymer. The complexity of pore structure and variability in pore size are reduced, leading to a more uniform pore distribution. Moreover, all microstructural parameters exhibit a strong correlation with the compression modulus. The results pertaining to the compressive and microstructural properties of loess reinforced with permeable polymer grouting can provide insights into the variations in the curing effect, serving as a theoretical foundation for the application of permeable polymer in loess treatment. [ABSTRACT FROM AUTHOR]

In this paper, we investigated Caputo fractional integro-differential equations with noninstantaneous impulses and nonlocal conditions. By employing the solution operator, the Mönch fixed point theorem, and the stepwise estimation method, we eliminated the Lipschitz condition of the nonlinear term, while also dispensing with the requirement for the compressibility coefficient condition 0 < k < 1. The main results presented represented a generalization and enhancement of previous findings. Furthermore, an example was provided to verify the application of our main results. [ABSTRACT FROM AUTHOR]

The unstable behavior of the isotropic, compressible Mooney-Rivlin hyperelastic model is investigated and described. The constitutive equation is parameterized with the help of the ground-state Poisson's ratio and the dimensionless ratio of the material parameters C 01 and C 10 . Transverse stretch solutions are obtained for standard homogeneous loading modes, and the stress solutions are computed numerically for the physically permitted range of the ground-state Poisson's ratio. We introduce a numerical technique to isolate subdomains with non-unique transverse stretch responses. Our analysis revealed some limitations of the model and allowed us to make critical observations about the strengths and weaknesses of the model. The analyses we present are essential to understand the characteristics of this widely used hyperelastic model. The novel results have important implications for the application of the isotropic, compressible Mooney-Rivlin hyperelastic material model. [ABSTRACT FROM AUTHOR]

The aqueous fluid (water) is accumulated near the interfaces between fractures (hydraulic and natural) and the matrix during hydraulic fracturing. The accumulated water can be partially removed either through the immediate well flow back or through shutting in well before the flow back. Which method is more effective for oil recovery? The answers are mixed in the literature from field reports and experimental or simulation studies. This article proposes a hypothesis that the flow back of fracturing fluid is controlled mainly by two mechanisms: viscous displacement and capillary imbibition. The shut-in can outperform the immediate flow, or vice versa, depending on reservoir and operation conditions. When the viscous displacement dominates, the immediate flow back is more effective. When the capillary imbibition dominates, the shut-in is more effective. The hypothesis is verified by the results of many simulation models which are built by modifying some parameters of the same base model. Those parameters include pressure drawdown, capillary pressure, matrix permeability, wettability, initial water saturation, and formation compressibility. It is implied from this study that the immediate flow back is preferred to the shut-in method if the capillary pressure is small; otherwise, the shut-in is preferred. [ABSTRACT FROM AUTHOR]

In this work, we study the pressure dependence of elastic constants of wurtzite indium nitride semiconductor based on Landau free energy expansion. Elastic constants are obtained as functions pressure up to second order. We have also evaluated the bulk modulus (B) and anisotropies of compressibility and shear for wurtzite indium nitride as functions of pressure. Agreement with previously obtained results based on first-principles calculations is found to be satisfactory. [ABSTRACT FROM AUTHOR]

The process of separating stages is crucial for multistage rockets, directly influencing the success of the launch plan. Different separation timing methods alter the flow field structure within the interlevel zone at separation, influencing the separation of the two-stage rockets. This paper employs the SST k-ω turbulence model to investigate the structure of the flow field and its aerodynamic and motion characteristics under different nozzle baffle opening and separation times, taking into account variable properties, supersonic compressibility, and the upstream–downstream interference. First, we examined the standard flow field structure, considering the engine jet, the lateral jet between stages, and the disturbance from the external supersonic inflow. Then, we discussed the displacement characteristics and axial force coefficient curves of the first and second steps of the separation process. Finally, we explored the impact of baffle opening and separation times on the flow field structure and axial force coefficients of the two stages at the onset of separation. For the flow field structure, a delay in the baffle opening and separation moment led to a gradual increase in downstream and separation regions until they stabilized after a certain range. However, the axial force coefficients displayed different behavior before and after the design point. [ABSTRACT FROM AUTHOR]

The volume change behaviour of an unsaturated compacted loess under thermo-hydro-mechanical loads is comprehensively investigated in this experimental research. A new temperature/suction-controlled triaxial apparatus with triple cells was developed. Temperature- and suction-controlled isotropic tests, heating–cooling tests with isotropic net stress and suction control and drying–wetting tests with isotropic net stress and temperature control were conducted on an unsaturated compacted loess from Shaanxi, China. Experimental results show that compressibility indices remain unchanged at various temperatures, but show different variation trends with changes in suction. Both suction hardening and thermal softening were observed. Irreversible volumetric contraction is induced in the compacted loess upon heating–cooling path and becomes more significant at higher isotropic net stresses and higher suctions. Lower over-consolidation ratio prior to heating results in greater irreversible contraction in loess samples. Water-holding capacity of loess samples decreases upon heating, but it is independent of the stress level. The hydraulic hysteresis of samples has no significant change with temperature changes. Slight shrinkage occurs during drying process in loess samples, and collapse can be observed in wetting process. Heating has limited effect on the drying shrinkage of loess samples but induces more distinctive wetting collapse. [ABSTRACT FROM AUTHOR]

The performance of energy geostructures is dependent on the surrounding soil properties in the presence of high temperatures or thermal cycles. Change in temperature may affect many engineering parameters of soils. Sand-bentonite mixtures or bentonite, which are used as a buffer should keep their performance at design level for a long time. Purpose: In order to improve engineering behavior of soils under high temperatures thermally durable materials may be used. Volume deformation and hydraulic conductivity behavior of 30% bentonite–70% sand mixtures in the presence of fiberglass additives were investigated. Methods: Consolidation tests were performed at room and high temperatures (80°C), hydraulic conductivity tests were started at room temperature, and a temperature cycle (25°C, 50°C, and 80°C) was applied. Results: Fiberglass increased the amount of compression insignificantly under room temperature, whereas the total compression amount increased remarkably under high temperature. On the other hand, the hydraulic conductivity increased under high temperature with fiberglass additive. Conclusions: Fiberglass-added sand-bentonite mixtures can be used around energy structures as an alternative buffer material with high-temperature resistance. [ABSTRACT FROM AUTHOR]

Two recent lower bounds on the compressibility of repetitive sequences, δ ≤ γ , have received much attention. It has been shown that a length-n string S over an alphabet of size σ can be represented within the optimal O (δ log n log σ δ log n ) space, and further, that within that space one can find all the occ occurrences in S of any length-m pattern in time O (m log n + o c c log ϵ n) for any constant ϵ > 0 . Instead, the near-optimal search time O (m + (o c c + 1) log ϵ n) has been achieved only within O (γ log n γ) space. Both results are based on considerably different locally consistent parsing techniques. The question of whether the better search time could be supported within the δ -optimal space remained open. In this paper, we prove that both techniques can indeed be combined to obtain the best of both worlds: O (m + (o c c + 1) log ϵ n) search time within O (δ log n log σ δ log n ) space. Moreover, the number of occurrences can be computed in O (m + log 2 + ϵ n) time within O (δ log n log σ δ log n ) space. We also show that an extra sublogarithmic factor on top of this space enables optimal O (m + o c c) search time, whereas an extra logarithmic factor enables optimal O(m) counting time. [ABSTRACT FROM AUTHOR]

The importance of high-speed water entry is acknowledged within the defense industry. This study numerically investigates the water entry of a high-speed rectangle projectile, focusing on cavity dynamics and shock wave generation. A computational model is employed to accurately simulate the intricate fluid dynamics of compressible multiphase flows. This model integrates a dual-phase flow algorithm with a thermally sensitive Tait equation of state for the liquid phase. The primary focus lies in understanding the effects of fluid compressibility on cavity evolution and shock wave propagation across different Froude numbers. The findings reveal that compressibility induces changes in cavity formation size, leading to significant variations in phase composition within the cavity. Furthermore, compressibility enhances the air cushion effect upon surface impact, resulting in delayed water entry and concurrent reduction in projectile drag. Moreover, a prognostic model is proposed, correlating shock pressure with propagation distance, thereby validating theoretical hypotheses advanced by Lee et al. [J. Fluid Struct., 11, 819–844 (1997)]. [ABSTRACT FROM AUTHOR]

The compaction of a fabric reinforcement in a Universal Testing Machine (UTM) allows to determine the achievable fiber volume fraction across a wide range of pressures, a valuable information for composite manufacturing. As seen in the first international compressibility benchmark, inaccuracies in the fabric stack thickness measurement, the approach to compliance correction and the non-parallelism between compaction plates resulted in highly inaccurate compression curves. In this paper, the different variability sources affecting indirect thickness methods, based on the machine displacement, and direct methods with laser sensors are presented and its impact on the accuracy is estimated. In conclusion, both thickness measurement methods produced similar results; however, the thickness measured by direct methods experienced more variability due to minor changes in the rig's displacement or the orientations between plates, combined with other sources of variability such as external interferences or vibrations from the compaction plate which led to variations in measurement precision throughout the tests. [ABSTRACT FROM AUTHOR]

This study investigated the compressibility of clay (Cc) for soft ground improvement and developed six optimized metaheuristic-based extreme learning machine (ELM) models (particle swarm optimization (PSO)-ELM, moth search optimization (MSO)-ELM, firefly optimization (FO)-ELM, cuckoo search optimization (CSO)-ELM, bees optimization (BO)-ELM, and ant colony optimization (ACO)-ELM) to predict Cc. A total of 739 laboratory tests were conducted to develop the models, and 517 datasets were used for training, while the remaining 222 samples were used for testing. The results showed that the accuracy of the developed models was improved by 3–5% compared to the original ELM model. The BO-ELM and MSO-ELM models were identified as the most effective models for predicting Cc, with accuracies ranging from 86.5% to 87%. The study suggests that the MSO-ELM model should be used if training time is critical. The developed models provide useful tools for predicting Cc, an essential parameter for soft ground improvement design, and can assist in the improvement of soft ground. [ABSTRACT FROM AUTHOR]

Recycling recently is the talk of the world in order not to pollute the environment. Nowadays, million tons of agricultural wastes are produced annually like eggshells (Abou-Hadid 2008). An experimental work program was done including different experiments like Atterberg limits, compaction, triaxial and consolidation tests. Soft clay soil samples are blended with 2 to 20% of eggshell powder with 2% increment. The findings revealed that eggshell powder addition reduced the plasticity of soil and increased the maximum dry density. Moreover, the shear strength was found to be increased with the increase of the eggshell powder content. It was found to be increased by 176% at 6% eggshell powder addition and then this value of the shear strength started to be decreased with the increase of eggshell powder. Finally, the void ratio of the soft clay is found to be decreased with the increase of the eggshell powder addition. [ABSTRACT FROM AUTHOR]

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The volumetric change in unsaturated loess during loading causes serious damage to the foundation and structure, accompanied by changes in hydraulic conditions. Therefore, quantifying the change in the load effect of loess under hydraulic coupling is of great significance for revealing the mechanism of hydraulic interaction. This study conducts isotropic compression and undrained shear tests on unsaturated compacted loess, simultaneously introducing the strength parameter η to enhance the Glasgow coupled model (GCM). The objective is to elucidate the hydraulic and mechanical coupling mechanism, where saturation increases under mechanical effects lead to strength degradation. The results show that saturation increases under mechanical effects improve the compressibility of the sample, and saturation has a direct impact on the stress–strain relationship. The increase in water content and confining pressure increases the trend of the critical state stress ratio M decreasing, and the strain softening trend increases. The compression of volume during shear tests increases the saturation, changes the hydraulic characteristics of loess, and affects the deformation and strength of loess. The modified GCM improves the applicability and prediction accuracy of unsaturated loess under the same initial state. The research results are of great significance for revealing the hydraulic and mechanical behavior of loess. [ABSTRACT FROM AUTHOR]

A technological scheme of casting with the imposition of pressure on the crystallizing metal by two pressing plungers is proposed. It is established that for an effective process of metal pressing, it is necessary to bring the magnitude and speed of pressure superposition into line with the temperature of the metal. To control the process, the control system must operate in the "Control by a given effect" mode. [ABSTRACT FROM AUTHOR]

In this article, using the structural parameters called the concentration-concentration fluctuation factor in the long wavelength limit, the number-number factor in the long wavelength limit, the partial number-mole fraction structural factor, the mixed structural factor in the long wavelength limit and calculating the short order factor Chemical field, we have studied the structure and relative investigation of interactions in two-component solutions including butyl acetate and normal alcohols (1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol) at a temperature of 298.15 degrees. Using the experimental values of molar volume and compressibility coefficient of the mixtures, the mentioned structural parameters were calculated. The effect of increasing the length of the alcohol chain on the mentioned parameters was studied, and using the obtained results, a discussion was made about the regularization or disorder of the solutions. The experimental values of the additional molar volume for all the mentioned systems are positive and increase with the increase of the length of the alcohol chain. The analysis of the mentioned structural parameters for binary mixtures also led to similar results for the strength of bonds and the amount of disorder in them. In general, it can be concluded that the intermolecular bonds in binary systems containing butyl acetate and normal alcohols are weak, and the amount of disorder in these solutions is greater than the amount of disorder in ideal solutions, and this disorder increases with the increase in the length of the alcohol chain. The increase of these irregularities, which is caused by the weakening of the bonds in the solution, can be considered as a result of the spatial hindrance caused by the non-polar chain of alcohols. With the increase in the length of the chain, the amount of this spatial hindrance also increases. [ABSTRACT FROM AUTHOR]

The low comprehensive compressibility coefficient characteristic of fracture-vuggy reservoirs often leads to imprecise dynamic reserve calculations. This study introduces a novel method for estimating dynamic reserves, which incorporates a modified comprehensive compressibility coefficient to enhance accuracy. This methodology has been applied to 23 wells in the Tahe Oilfield, resulting in error rates substantially lower than those associated with traditional techniques, thereby markedly enhancing the accuracy of dynamic reserve estimations. Specifically, for karst cave and fracture-vuggy reservoirs, the error rate in dynamic reserve calculations is reduced to under 10%, surpassing conventional methods by more than fivefold. In the case of fractured reservoirs, despite minor fluctuations in error rates due to stress sensitivity, diversion capacity, and channel variations, the proposed method still demonstrates a significant reduction in error rates compared to standard practices. [ABSTRACT FROM AUTHOR]

The compressibility of composite materials obtained by impregnation with water dispersion of polyurethane webs made of polyethylene terephthalate fibers with a diameter of 20 μm and a mixture of these fibers with polyethylene terephthalate fibers with a diameter of 42 μm is investigated. The influence of the composition on the formation of the structure of canvases and composite materials based on them is shown. In the process of heat treatment, the volume of webs made of fibers with a diameter of 20 μm increases and decreases for webs based on a mixture of fibers of different diameters. Compared with canvases with a degree of impregnation less than 1.0, the water permeability of materials of various compositions increases by 1.5–2.0 times. A model is proposed to predict the degree of compressibility of composite materials from the degree of impregnation and load. It is established that the compressibility of composite materials decreases when using a web as a fibrous filler in which the fibers are oriented perpendicular to the surface of the web. Less effective for reducing compressibility is the use of a web made of a mixture of fibers of different diameters as a fibrous filler. [ABSTRACT FROM AUTHOR]

Expansive soils sensitivity to volumetric change is one of the well-known challenges in the field of geotechnical engineering. Various attempts have been made by researchers to solve this problem. Current research presents the effect of human hair fibers on the behavior of expensive soils. A reconstituted soil of 80% kaolin as raw material and 20% bentonite with different percentages of human hair (0%, 0.5%, 1%, 1.5% and 2%) was used. The microstructure of the formulations was characterized by studying the interactions between soil and human hair using scanning electron microscopy (SEM). The microstructure of the formulations was characterized by studying the interactions between soil and human hair using scanning electron microscopy (SEM). Atterberg limits, compaction characteristics, swelling parameters, compressibility and shear strength were also examined. The results of this study indicate that the inclusion of human hair fibers significantly improves the properties of the expansive soil mixture. These results open up new prospects for the stabilization of expansive soils. [ABSTRACT FROM AUTHOR]

This study comprehensively explores the compaction and compressibility characteristics of snail shell ash (SSA) and ground-granulated blast-furnace slag (GBFS) in stabilizing local bentonite for landfill baseliner applications. The untreated soil, with a liquid limit of 65%, plastic limit of 35%, and plasticity index of 30%, exhibited optimal compaction at a moisture content of 32% and a maximum dry density of 1423 kg/m3. SSA revealed a dominant presence of 91.551 wt% CaO, while GBFS contained substantial 53.023 wt% SiO2. Treated samples with 20% GBFS and 5% SSA exhibited the highest maximum dry density (1561 kg/m3) and optimal moisture content (13%), surpassing other mixtures. The 15% SSA-treated sample demonstrated superior strength enhancement, reaching an unconfined compressive strength of 272.61 kPa over 28 days, while the 10% GBFS-treated sample achieved 229.95 kPa. The combination of 15% SSA exhibited the highest shear strength (49 kPa) and elastic modulus (142 MPa), showcasing robust mechanical properties. Additionally, the 15% SSA sample displayed favourable hydraulic conductivity (5.57 × 10–8 cm/s), outperforming other mixtures. Notably, the permeability test, a critical aspect of the study, was meticulously conducted in triplicate, ensuring the reliability and reproducibility of the reported hydraulic conductivity values. Treated samples with SSA and GBFS showed reduced compressibility compared to the control soil, with the 15% SSA-treated sample exhibiting a more consistent response to applied pressures. Scanning Electron Microscopy analysis revealed substantial composition changes in the 15% SSA mixture, suggesting its potential as an effective base liner in landfill systems. In conclusion, the 15% SSA sample demonstrated superior mechanical properties and hydraulic conductivity, presenting a promising choice for landfill liner applications. [ABSTRACT FROM AUTHOR]

Extended framework materials with specific topologies can exhibit unusual mechanical behaviour, such as expanding in one direction under hydrostatic (uniform) pressure, known as negative linear compressibility (NLC). Here, two hybrid perovskite frameworks with winerack structures, a known NLC topology, are investigated under pressure. [C(NH2)3]Er(HCO2)2(C2O4) exhibits NLC from ambient pressure to 2.63(10) GPa and is the first reported NLC hybrid perovskite from ambient pressure. However, isostructural [(CH3)2NH2]Er(HCO2)2(C2O4) instead compresses relatively moderately along all axes before it undergoes a phase transition above 0.37(10) GPa. The differences in the mechanical properties can be interpreted from differences in host–guest interactions within these frameworks, primarily their hydrogen bond networks. [ABSTRACT FROM AUTHOR]

Extended framework materials with specific topologies can exhibit unusual mechanical behaviour, such as expanding in one direction under hydrostatic (uniform) pressure, known as negative linear compressibility (NLC). Here, two hybrid perovskite frameworks with winerack structures, a known NLC topology, are investigated under pressure. [C(NH2)3]Er(HCO2)2(C2O4) exhibits NLC from ambient pressure to 2.63(10) GPa and is the first reported NLC hybrid perovskite from ambient pressure. However, isostructural [(CH3)2NH2]Er(HCO2)2(C2O4) instead compresses relatively moderately along all axes before it undergoes a phase transition above 0.37(10) GPa. The differences in the mechanical properties can be interpreted from differences in host–guest interactions within these frameworks, primarily their hydrogen bond networks. [ABSTRACT FROM AUTHOR]

Pressure‐induced swelling has been reported earlier for several hydrophilic layered materials. MXene Ti3C2Tx is also a hydrophilic layered material composed by 2D sheets but so far pressure‐induced swelling is reported for this material only under conditions of shear stress at MPa pressures. Here, high‐pressure experiments are performed with MXenes prepared by two methods known to provide "clay‐like" materials. MXene synthesized by etching MAX phase with HCl+LiF demonstrates the effect of pressure‐induced swelling at 0.2 GPa with the insertion of additional water layer. The transition is incomplete with two swollen phases (ambient with d(001) = 16.7Å and pressure‐induced with d(001) = 19.2Å at 0.2 GPa) co‐existing up to the pressure point of water solidification. Therefore, the swelling transition corresponds to change from two‐layer water intercalation (2L‐phase) to a never previously observed three‐layer water intercalation (3L‐phase) of MXene. Experiments with MXene prepared by LiCl+HF etching have not revealed pressure‐induced swelling in liquid water. Both MXenes also show no anomalous compressibility in liquid methanol. The presence of pressure‐induced swelling only in one of the MXenes indicates that the HCl+LiF synthesis method is likely to result in higher abundance of hydrophilic functional groups terminating 2D titanium carbide. [ABSTRACT FROM AUTHOR]

The calculation of the influx index is one of the most contentious issues in dynamic reserve evaluation of gas reservoirs' development. For the influx index, it is key to obtain information on the pore compressibility coefficient under realistic gas reservoir pressure. So far, little is known about the assessment of the pore compressibility coefficient at a laboratory scale. Here, we combine observations of gas flowmeter, ISCO booster pump, intermediate container, and rock samples to quantify the pore compressibility coefficient from the KL2-13 well in the Kela-2 reservoir. Additionally, the iterative method (combined the static and dynamic methods) is proposed based on the experimentally obtained pore compressibility coefficient (Cf), dynamic reserve (G), water body multiple (β), and material balance equation to calculate the influx index. The combined iterative method adjusts the values of G and N by comparing the results of the static and dynamic methods, and iteratively corrects Cf using a binary search method until the results of the static and dynamic methods are consistent. The results of our study reveal that the influx index calculated by the dynamic and static methods was consistent, and the gas production per unit pressure drop matched the actual production. These results strongly suggest that there exists a correlation between formation pressure and the influx index, wherein the latter exhibits a gradual decrease as the former decreases. Conversely, the displacement index of both the rock and connate water do not demonstrate a significant dependence on pressure. Furthermore, the impact of pressure on the pore compressibility factor and reservoir water compressibility factor appears to be minimal. These findings hold substantial implications for understanding the behavior of gas reservoirs under varying pressure conditions. [ABSTRACT FROM AUTHOR]

Soft clay is characterized by high compressibility, low permeability, low strength, and high water content, making it a poor substrate for construction. Hence, soil treatment is often required for soft clay. However, the traditional treatment methods, such as stacking and on-site mixing, involve large space, long time, and high cost. In contrast, lime is stable and cheap, but slow to set and harden. In this paper, the microbially induced carbonate precipitation (MICP) and lime composite curing of soft clay was investigated. Tests were carried out on soft clay samples with different lime ratios. By comparing the changes of strength, composition, and microstructure before and after curing, the mechanism of MICP/lime composite solidification of soft clay was systematically studied. The results showed that (1) a reasonable proportion of lime can react with water and CO2 in clay to generate CaCO3 , and also promote the induction of more CaCO3 precipitation by microorganisms, contributing to the improved strength of solidified clay; (2) MICP/lime composite curing can effectively reduce water in soft clay and help to improve the strength of solidified soil; (3) MICP and lime were complementary in terms of curing time, leading to continuous improvement of curing effect; and (4) the MICP/lime composite has a good effect on the solidification of soft clay. Under the experimental conditions in this study, the best solidification effect was observed for soft clay with a water content of 30% and a lime ratio of 30%. [ABSTRACT FROM AUTHOR]

Diurnal freeze–thaw process occurs in the Lianghekou area in winter, which will affect the construction progress and quality of the project. In this paper, the compressibility of clay experiencing the freeze–thaw (F-T) cycles under different impacting factors was investigated. A series of unidirectional F-T tests were carried out in a closed system, and the compressibility tests were carried out for the same specimens underwent F-T cycles to study the compressibility along the specimen height. The experimental results demonstrate that the initial moisture content of specimens, the cooling temperature, and the number of F-T cycles affect the compressibility of specimens. As the cooling temperature decreases, the initial moisture content or the number of F-T cycles increases, the compressive strain of the affected zone of specimens increases under the same vertical pressure, while the confined compressive modulus decreases. The variation of the compressibility for the unaffected zone is different from that for the affected zone. For the same impacting factor, the compressive strain of the affected zone is greater than that of the unaffected zone, while the confined compressive modulus of the former is less than that of the latter. The change of compressibility is mainly affected by the characteristics of cryostructure and moisture migration of the specimen after F-T. This research may provide some guidance for the engineering construction process in winter in the seasonally frozen ground region. [ABSTRACT FROM AUTHOR]

This paper presents a coupled model that considers the nonlinear compressibility effect in fluid–structure interaction (FSI) during air-blast loading on flexible structures. In this coupled model, structural behaviour is idealized as a linear single-degree-of-freedom mass-spring-damper system whereas nonlinear fluid compressibility is considered by applying Rankine–Hugoniot jump conditions across a moving plate. The surrounding fluid medium is modelled with an ideal gas equation and hence, this model can be applied for FSI analysis with relatively strong shocks (reflection coefficient of up to 8). The nonlinear compressibility of the fluid medium at the backside of the plate is also considered in this coupled formulation and its effects on the structural responses are examined. Moreover, the negative/underpressure phase of the reflected wave profile, which is typically neglected in a decoupled model, is also considered in the proposed model and its influence on the structural response is also investigated. The study reveals that the nonlinear compressibility of fluid medium significantly influences the coupled FSI phenomena, especially in flexible lightweight structures. Numerical examples are presented to highlight the implications of the nonlinear compressibility effect in FSI on the reflected pressure profile and the response of flexible structures. Parametric dependencies of response on structural mass and natural frequency are examined thoroughly and a response spectrum is obtained. It is envisaged that the lightweight protective structure design under higher blast intensity may benefit from this study. [ABSTRACT FROM AUTHOR]