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The wetting behavior of shale oil and gas on shale surfaces is determined by the interplay of organic matter (OM), mineral composition, and the intricate pore network structure of the shale. In this paper, the sensitivity responses of the Frenkel–Halsey–Hill (FHH), Neimark (NM), and Wang–Li (WL) fractal models to marine shale with varying material components are analyzed, based on liquid nitrogen adsorption experiments and fractal theory. The wettability evolution model of shale with different maturity stages is established to reveal the heterogeneity characteristics of wettability in shale with complex pore structures. Results show that the NM and WL models offer distinct advantages in evaluating the reservoir structure of shale oil and gas resources. The existence of large-diameter pores is conducive to the homogeneous development of the pore structure. The coupling relationship between pore volume, pore size and pore specific surface affects the fractal characteristics of the pore structure. For highly overmature shale, with an increase in fractal dimension, the wettability of shale changes from neutral-wet to water-wet. For ultramature shale, the higher heterogeneity of the pore structure leads to larger contact angles, causing the wettability to transition gradually from water-wet to oil-wet. In addition, the sensitivity analysis of wettability to fractal structure parameters is examined from the perspective of OM maturation and evolution. [ABSTRACT FROM AUTHOR]

Concrete, as the most widely used construction material in civil engineering, plays a crucial role in the durability and safety of structures. In recent years, with the deepening understanding of concrete's microstructure, researchers have begun to explore the intrinsic relationship between its microfeatures and mechanical properties. However, existing characterization methods largely focus on analyzing the mechanical behavior of concrete from a macroscopic perspective, lacking a comprehensive and quantitative description of its microstructure. Traditional experimental techniques such as Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) can reveal the microscopic morphology of concrete but are still unable to precisely analyze the quantitative relationship between the pore structure of concrete and its mechanical performance. Thermodynamic analysis, as a tool capable of effectively revealing the internal physical properties and mechanical behavior of materials, provides a new approach for the characterization of concrete's microstructure. This study primarily explores the relationship between concrete's microstructure and mechanical properties based on thermodynamic principles. Firstly, a thermodynamics-based fractal model for civil engineering concrete is proposed, where the pore structure and fractal features of concrete are analyzed from a thermodynamic perspective to further uncover the regularities of its mechanical behavior. Secondly, the study investigates the relationship between compressive strength and pore structure of concrete under high-temperature conditions, analyzing the effects of high temperatures on the evolution of concrete's pore structure and its mechanical performance. Through these studies, this paper not only introduces new analytical methods for the microstructural characterization of concrete materials but also provides a theoretical foundation for the performance prediction and optimized design of concrete in high-temperature environments. [ABSTRACT FROM AUTHOR]

In this paper, 12 sandstone samples are collected from the Taiyuan Formation in Qinshui Basin, and sample types using the T2 spectral under LF-NMR saturation and centrifugation conditions are classified. Moreover, single and multifractal models were used to calculate fractal parameters of saturated and centrifugal T2 spectra, and the correlation between different fractal parameters, pore structure, T2cutoff value, and pore permeability parameters was studied. The results are as follows. (1) According to the T2 spectrum curves under centrifugation and saturation conditions, all the samples can be divided into three types. There are significant differences in the uniform pore size distribution. However, the non-uniformity of small pore distribution in type B samples is stronger than that of other types, while heterogeneity of large pore distribution is weaker than that of different types. The centrifugal T2 spectrum curve exhibits both single-fold and multifractal characteristics. The results of a single fractal by using a centrifugal T2 spectrum are consistent with those of a saturated T2 spectrum, indicating that single fractal features by using centrifugal and saturated T2 spectra are consistent. Unlike the single fractal parameters, the correlation between the saturation and centrifugal T2 spectrum's multifractal parameters is weak. This suggests that the physical significance conveyed by the centrifugal T2 spectrum's multifractal parameters differs from that of the saturated T2 spectrum. [ABSTRACT FROM AUTHOR]

The nuclear magnetic resonance T2 spectrum was used to identify the T2 cut-off value, which is the key to determining the irreducible water saturation of a reservoir. In this paper, the saturation and centrifugal T2 spectra of sandstone and coal samples were used to explore the correlation between each parameter and the T2 cut-off value, using a single fractal dimension, a multifractal dimension and a spectral morphology discrimination method. The conclusions are as follows: (1) The T2 spectra of nine sandstone samples in this paper can be divided into four types. Type A is represented by sample 2, wherein the T2 spectrum shows a bimodal state and the area of the right T2 spectrum (2.5~100 ms) is larger than that of the left T2 spectrum (T2 < 2.5 ms), indicating that the sample has good pore connectivity and belongs to the macroporous development sample. The B-type T2 spectrum is unimodal, and the pore connectivity is poor, indicating that it is a large-pore development sample. The T2 spectrum of the C-type sample is unimodal, and the pore connectivity is very poor, indicating that it is a mesoporous development sample. The T2 spectrum of the D-type sample shows a single peak state, and the main T2 is distributed within 0.1~2.5 ms. The pore connectivity is very poor, which indicates that it belongs to the small pore development type sample. (2) The single fractal model shows that, compared with other single fractal parameters, D2 increases with the increase in the T2 cut-off value, but the correlation is weak. Therefore, it is not feasible to predict the T2 cut-off value using the single fractal dimension parameter. (3) The multifractal model shows that D−10–D10 increases linearly with the increase in D−10–D0, but there is no obvious linear correlation between D0–D10 and D−10–D10, indicating that the low pore volume area in this kind of sample controls the overall heterogeneity of pore distribution. (4) The related parameters affecting the T2 cut-off value include D−10–D10, D−10/D10, D−10–D0, TM and D2. Therefore, based on the above five parameters, a T2 cut-off value prediction model is constructed. The T2 cut-off value calculated by the model is highly consistent with the experimental value, which proves the reliability of the model. [ABSTRACT FROM AUTHOR]

Spontaneous imbibition (SI) is an important mechanism for enhancing oil recovery in low-permeability reservoirs. Due to the strong heterogeneity, and the non-Darcy flow, the construction of SI model for lowpermeability reservoirs is extremely challenging. Commonly, traditional SI models based on single or averaged capillary tortuosity ignore the influence of heterogeneity of pore seepage channels and the threshold pressure (TP) on imbibition. Therefore, in this work, based on capillary model and fractal theory, a mathematical model of characterizing SI considering heterogeneity of pore seepage channels is established. On this basis, the threshold pressure was introduced to determine the pore radius at which the wetted phase can displace oil. The proposed new SI model was verified by imbibition experimental data. The study shows that for weakly heterogeneous cores with permeability of 0-1 mD, the traditional SI model can characterize the imbibition process relatively accurately, and the new imbibition model can increase the coefficient of determination by 1.05 times. However, traditional model has serious deviations in predicting the imbibition recovery for cores with permeability of 10e50 mD. The new SI model coupling with heterogeneity of pore seepage channels and threshold pressure effectively solves this problem, and the determination coefficient is increased from 0.344 to 0.922, which is increased by 2.68 times. For low-permeability reservoirs, the production of the oil in transitional pores (0.01-0.1 mm) and mesopores (0.1-1 mm) significantly affects the imbibition recovery, as the research shows that when the heterogeneity of pore seepage channels is ignored, the oil recovery in transitional pores and mesopores decreases by 7.54% and 4.26%, respectively. Sensitivity analysis shows that increasing interfacial tension, decreasing contact angle, oilewater viscosity ratio and threshold pressure will increase imbibition recovery. In addition, there are critical values for the influence of these factors on the imbibition recovery, which provides theoretical support for surfactant optimization. [ABSTRACT FROM AUTHOR]

Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

High energy consumption is a serious issue associated with in situ thermal desorption (TD) remediation of sites contaminated by petroleum hydrocarbons (PHs). The knowledge on the thermophysical properties of contaminated soil can help predict accurately the transient temperature distribution in a remediation site, for the purpose of energy conservation. However, such data are rarely reported for PH-contaminated soil. In this study, by taking diesel as a representative example for PHs, soil samples with constant dry bulk density but different diesel mass concentrations ranging from 0% to 20% were prepared, and the variations of their thermal conductivity, specific heat capacity and thermal diffusivity were measured and analyzed over a wide temperature range between 0°C and 120°C. It was found that the effect of diesel concentration on the thermal conductivity of soil is negligible when it is below 1%. When diesel concentration is below 10%, the thermal conductivity of soil increases with raising the temperature. However, when diesel concentration becomes above 10%, the change of the thermal conductivity of soil with temperature exhibits the opposite trend. This is mainly due to the competition between soil minerals and diesel, because the thermal conductivity of minerals increases with temperature, whereas the thermal conductivity of diesel decreases with temperature. The analysis results showed that, compared with temperature, the diesel concentration has more significant effects on soil thermal conductivity. Regardless of the diesel concentration, with the increase of temperature, the specific heat capacity of soil increases, while the thermal diffusivity of soil decreases. In addition, the results of a control experiment exhibited that the relative differences of the thermal conductivity of the soil samples containing the same concentration of both diesel and a pure alkane are all below 10%, indicating that the results obtained with diesel in this study can be extended to the family of PHs. A theoretical prediction model was proposed based on cubic fractal and thermal resistance analysis, which confirmed that diesel concentration does have a significant effect on soil thermal conductivity. For the sake of practical applications, a regression model with the diesel concentration as a primary parameter was also proposed. [ABSTRACT FROM AUTHOR]

A stress-dependent porosity and permeability model is proposed to predict the microstructure evolution and the physical properties and mechanical behavior of deformable hydrate-bearing sediments (HBS) with various hydrate growth patterns under engineering disturbance. First, according to Hertzian contact theory and the proposed mesoelastic–plastic damage model (Gurson-DP model), the correction formula of the pore size under the influence of the effective confining pressure and the overburden pressure is given, and the stress-dependent porosity model is derived. Second, the fractal capillary bundle model is used to describe the stress-dependent permeability of HBS with different hydrate saturations considering the grain-cementing hydrate and the universal-growth hydrate. Finally, the proportions of hydrates with various growth patterns, such as pore filling (PF), wall coating (WC), and grain cementing (GC), are determined based on the equivalent flow assumption to reasonably evaluate the hydrate growth habit in HBS. This paper comprehensively studies the stress-dependent porosity and permeability models of deformable HBS and thus, provides a theoretical basis for quantitative evaluation and prediction of the physical properties (such as porosity and permeability) and mechanical behavior of HBS. [ABSTRACT FROM AUTHOR]

In order to study the contact stiffness of the bonding surface in more detail from the perspective of fractal theory, on the basis of the M-B fractal model and the Hertz theory, a domain expansion factor is introduced to represent the fractal dimension to establish the normal and tangential contact stiffness fractal models of the bonding surface, respectively. The model comprehensively considers the effects of load, fractal dimension and material parameters on the contact stiffness. At the same time, the change trend of the contact stiffness of the joint surface and each parameter is obtained through numerical simulation.The change trend of normal contact stiffness and normal load is the same, which is opposite to the fractal characteristics and length scale coefficient, but the change trend of the fractal dimension is more complicated, no longer monotonic. The changetrend caused by tangential contact stiffness and the above parameters is similar to that caused by normal contact stiffness.

The occurrence and production of coalbed methane is related to the development degree of pore system in coal reservoirs. The pore structure characteristics of original structural coal seam will change significantly after damage and deformation, thus affecting the adsorption/desorption and diffusion process of coalbed methane. Through the low-temperature liquid N2 and low-pressure CO2 adsorption analysis and isothermal adsorption experiments on coal with different structures from the No. 3 coal seam in Zhaozhuang coalfield in Qinshui Basin, the variation laws of pore structure and adsorption of coals with various destructive strengths were analyzed. Applying experimental data and numerical fractal modeling, the pore fractal characteristics of coal with different structures and their effects on methane adsorption and diffusion in coal were revealed. The results shown that with the increase of the destructive intensity of coal structures, the specific surface area and pore volume of coal increased, the proportion of 50-300 nm pores gradually decreased, the micropores and mesopores of 2-50 nm and ultra-micropores of less than 2 nm increased. As the main adsorption pores in coal, the ultra-micropores size was mainly distributed in 0.45-0.65 nm and 0.80-1.0 nm. The adsorption amount of N2, CO2 and CH4 increased with the increasing destructive degree of coal structure. The order of adsorption capacity from large to small was: intact coal>mylonitic coal > granulated coal > cataclastic coal. The fractal dimensions of the micro-, meso- and macro-porous structures indicated that the pore structure of tectonically deformed coals will be simplified. Coal with a higher damage intensity had a rougher pore surface (corresponding to a higher D1) and a more homogeneous pore size distribution (corresponding to a lower D2). The fractal dimension of ultra-microporous (Dm) gradually increased with the increasing structural destruction intensity of coal, and was positively correlated with Langmuir constant (VL) and the corresponding specific surface area, indicating that the increase of coal surface roughness led to the increase of specific surface area, which provided more adsorption points with high adsorption potential for gas adsorption and enhanced the adsorption capacity of coal. The effective diffusion coefficient and pore volume were positively correlated with the fractal dimensions D1 and negatively correlated with D2, which indicated better pore connectivity, increased pore volume, improved gas inlet and outlet efficiency, and enhanced gas diffusion efficiency of destroyed intact coal.

The hydraulic conductivity of frozen soil is crucial for predicting water migration and frozen heave. Many models have been proposed to estimate the hydraulic conductivity, which involves factors such as unfrozen water content, specific surface area, grain size distribution, and pore size distribution. However, the bottleneck effect on the hysteresis of unfrozen water has not been adequately considered. This study proposed a hydraulic conductivity model based on the fractal theory by assuming the capillary tubes with a pore throat. Subsequently, the hydraulic conductivity was expressed as the product of the saturated and relative hydraulic conductivity, both of which can be determined from the microscopic fractal characteristics. Finally, the proposed model was verified using the experimental data and existing models, and a sensitivity analysis of the relative hydraulic conductivity was conducted. The validation showed that the predicted results agree well with the experimental data. Meanwhile, the proposed model can better describe the hysteresis effect of unfrozen water content during the freezing-thawing process than other commonly used models. Relative hydraulic conductivity is sensitive to pore structure characteristics and unfrozen water content. Immobile water saturation evidently influenced the relative hydraulic conductivity when it reached 0.7. The proposed model can be simplified as a power function in which the exponent can be calculated using the fractal dimension. The results help simulate the dynamic process of unfrozen water in frozen soil and may help understand the complex mechanisms of hysteresis and transport processes in frozen soil.

AbstractThis study presents a comprehensive investigation into the intricacies of single-phase simulation concerning the behavior of fractal interfacial magnetized metallic chemical-reactive nanoparticles within fluid systems. The research focuses on unraveling the multifaceted phenomena associated with heat and mass transfer in complex nanoscale environments. To achieve this, we employ numerical techniques to address the intricate fluid flow problems that arise due to the presence of these nanoparticles. Fractal complexities are linked to critical phenomena, such as mixing and mass transport, at the turbulent/non-turbulent interface of shear layers and boundary layers. This study primarily concentrates on the phenomena of heat and mass transfer, with a focus on estimating thermal conductivity models that have significant impacts on the flow of metallic nanofluids under convective conditions. The combination of a high thermal conductivity model with a novel interfacial fractal theory reveals a substantial effect on heat and mass transfer enhancement. Furthermore, this research explores hybrid types of porous channel geometries under the combined influence of magnetohydrodynamics and chemical reaction mechanisms in the presence of metallic nanoparticles. A comprehensive numerical analysis of higher-order nonlinear differential equations is conducted, which exposes the flow field’s behavior concerning momentum, energy, and mass transfer. These insights are envisioned through single-phase simulations of nanofluids. The influence of the nanoparticles’ radius and diameter is found to play a significant role in thermal performance, with nanoparticles ranging from 1% to 8% exhibiting a notable impact on thermal conductivity. HighlightsA new mathematical relation of mass, as well as heat transfer for metallic-nanomaterial being affected by thermal conductivity (T.C.), has been established.The important role of the physical number is observed under the effect of T.C. and heat and mass transfer through orthogonal porous surfaces.An injection/suction, as well as an expansion/contraction phenomenon related to the porous surface is observed.A new mathematical relation of mass, as well as heat transfer for metallic-nanomaterial being affected by thermal conductivity (T.C.), has been established.The important role of the physical number is observed under the effect of T.C. and heat and mass transfer through orthogonal porous surfaces.An injection/suction, as well as an expansion/contraction phenomenon related to the porous surface is observed. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mechanical Strength / Jixie Qiangdu is the property of Zhengzhou Research Institute of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The contact parameters of joint interfaces have a great influence on the dynamic performance of the machine tool, and the dynamic performance determines the machining precision of the machine tool. Therefore, it is important to accurately identify the contact parameters of joint interfaces to improve the machining precision of the machine tool. In this paper, a method of identifying the joint interface stiffness parameters based on a joint simulation in Matlab and Ansys is first proposed, and then stiffness parameters of joint interfaces between the bed and column of the precision grinding machine are identified by applying the method. Finally, the feasibility and high efficiency of the proposed method are proved by comparing the natural frequencies of the simulation and the experiment. In order to further analyze the influence of joint contact parameters on the performance of the joint interfaces, the theoretical model of the normal stiffness of the joint interfaces based on fractal geometry is amended and verified by taking into account the asperity interaction and elastic–plastic deformation. Then, the modified model is extended to a three-dimensional model, which is more in line with the actual situation. Finally, the influencing factors of the joint interface stiffness are analyzed. The conclusions of this paper are of great significance in the dynamic performance analysis and structural design of machine tools. [ABSTRACT FROM AUTHOR]

Grain boundary engineering (GBE) is designed for metals to optimize the grain boundary characteristics and improve their resistance to intergranular corrosion (IGC). In this study, the effect of various GBE processing on the fraction of low ΣCSL grain boundaries and random large-angle grain boundary connectivity in 304 stainless steel was investigated quantitatively with a fractal model. The corrosion weight loss rate, corrosion current density and sensitization degree of samples with various grain boundary characteristics were measured, and these corrosion behaviors were studied in term of the fractal dimension. The results showing the specimen after alternating directions cold rolling plus annealed at 1100 °C obtained the highest ΣCSL score that was 67.4%. And the value of fractal dimension for specimen after solid solution annealing, cold rolled 5% or cold rolled 20% reduction plus annealed at 1100 °C for 5 min in GBE was 1.75, 1.53 and 1.46, respectively. An indicator defined by fractal dimension for grain boundary characteristic on corrosion behaviors of 304 stainless steel was verified and clarified, and the mechanisms of GBE to improve corrosion resistance were confirmed with the observation of low-energy grain boundary fragments introduced by annealing twins and triple junctions in grain boundaries.

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The innovation of structural forms and the increase in the energy-saving requirements of buildings have led to higher requirements regarding the application conditions of steel slag foam concrete (SSFC) to ensure that the SSFC has a lower thermal conductivity and sufficient compressive strength, which has become the primary research object. Through a comprehensive consideration of 7 d compressive strength and thermal conductivity, the recommend mix ratio of SSFC was as follows: maximum SS size = 1.18 mm, water–cement ratio = 0.45, replacement rate of SS = 20–30%. Moreover, a theoretical formula was derived to determine thermal conductivity versus porosity based on fractal theory. The measured values of the foam concrete found elsewhere corroborate the fractal relationship regarding thermal conductivity versus porosity. This fractal relationship offers a straightforward and scientifically sound way to forecast the thermal conductivity of SSFC. [ABSTRACT FROM AUTHOR]

The physicochemical properties of “smart” or stimuli-sensitive amphiphilic copolymers can be modeled as a function of their environment. In special, pH-sensitive copolymers have practical applications in the biomedical field as drug delivery systems. Interactions between the structural units of any polymer-drug system imply mutual constraints at various scale resolutions and the nonlinearity is accepted as one of the most fundamental properties. The release kinetics, as a function of pH, of a model active principle, i.e., Curcumin, from nanomicelles obtained from amphiphilic pH-sensitive poly(2-vinylpyridine)-b-poly(ethylene oxide) (P2VP-b-PEO) tailor-made diblock copolymers was firstly studied by using the Rietger-Peppas equation. The value of the exponential coefficient, n, is around 0.5, generally suggesting a diffusion process, slightly disturbed in some cases. Moreover, the evaluation of the polymer-drug system’s nonstationary dynamics was caried out through harmonic mapping from the usual space to the hyperbolic one. The kinetic model we developed, based on fractal theory, fits very well with the experimental data obtained for the release of Curcumin from the amphiphilic copolymer micelles in which it was encapsulated. This model is a variant of the classical kinetic models based on the formal kinetics of the process.

Soil–water characteristic curve (SWCC) and suction stress characteristic curve (SSCC), as the core of unsaturated soil mechanics, are important constitutive relationship curves for unsaturated soils, which can accurately describe the stress state in the soil. This paper examines the pore size distribution curves (PSD) of loess collected from Yan'an, China, by performing nuclear magnetic resonance (NMR) tests. In this paper, the Young–Laplace theory and the fractal model are combined with the PSD to establish the relationship between matric suction and volumetric water content. Finally, it establishes a mathematical model for predicting SWCC and SSCC. In addition, the evolution of SWCC and SSCC under different dry densities of compacted loess was studied based on the predictions. The study found that pore volumes with pore diameters smaller than the critical pore diameter could be used to predict the residual water content. Additionally, the water-holding capacity can be expressed in terms of the fractal dimension, which is controlled by the PSD. Based on the rapid characteristics of the NMR test, this paper makes a rapid prediction of SWCC and SSCC. It gives a new idea for the subsequent rapid testing of SWCC and SSCC. [ABSTRACT FROM AUTHOR]

The pore-structure characteristics of hybrid basalt–polypropylene fibre-reinforced concrete were investigated by using mercury intrusion porosimetry. The applicability of various fractal models in characterising the HBPRC pore structure was compared. The results show that the types and content of fibres show different influences on the cumulative pore volume and fractal characteristics of hybrid basalt-polypropylene fibre-reinforced concrete. Compared with pore-volume and solid mass, the fractal characteristics of pore surface area of hybrid basalt-polypropylene fibre-reinforced concrete is more significant. Furthermore, the pore-surface fractal model that established based on the energy conservation relationship during mercury intrusion is more accurate and effective for the characterization of fractal dimension of hybrid basalt-polypropylene fibre-reinforced concrete. The research results can provide important theoretical guidance for the study of pore structure and fractal characteristics of fibre-reinforced concrete.

The Lut Block is a potential porphyry-style mineralized region in Iran including the well-explored Shadan porphyry gold-copper deposit, which has an extensive zone of gold- and copper-bearing stockwork-like sheeted veins. The structural setting of this deposit is a key to understanding the genesis of the mineralization. Our field studies show that the mineralization occurs as steeply dipping ore bodies along NW–SE transpressional faults. The zones with a high frequency of veins and volume of veins have a NW–SE trend, which is closely related to transpressional faults. We propose that such a compressional regime inhibits focused ore-forming fluid flow to higher levels in the crust. After a local change in stress field, fluid depressurization and channeling along transpressional faults generated the sheeted veins. This indicates an important role of these transpressional faults in focusing and controlling mineralization within this porphyry deposit, which has important implications for the exploration of porphyry deposits on a regional scale. The spatial distribution of sheeted veins is used to examine gold anomalies from lithogeochemical data extracted by fractal models. The results show that a combination of high vein density and high vein volume areas with gold anomalies could result in identifying areas with greater potential at the deposit to regional scale. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Science & Engineering (1673-2812) is the property of Journal of Materials Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Land resources in cities are limited, and the cost of green space construction is high. Compared with increasing the amount of green space, maximizing the cooling effect of limited green space has important theoretical and practical significance. Green fractal is a new innovative branch of urban fractal that uses a fractal index to quantify the green space structural index in studying the thermal environmental effect. Multi-source data, such as high-resolution remote sensing images, were used, and spatial regression models and inconsistency indices were applied to explore the spatial pattern of the urban thermal environment at the block scale, and the mechanism of green space fractal characteristics in terms of correlation and spatial heterogeneity, to assess the quality of green space development. This study shows the following: (1) In 2019, the land surface temperature in Dalian formed a spatial distribution structure of "high in the central region and low in the surrounding region" at the block scale, and the fractal indices of different green spaces show the spatial distribution structure of "dual-core" and "multi-core" spaces. (2) The driving direction and force of the fractal index of green space on the spatial pattern of land surface temperature differs. The influence of the green space structure index (grid and boundary dimensions) is greater than that of the quantity index (area and circumference), and the influence of the grid dimension is the most significant. (3) The spatial heterogeneity between the fractal index of block-scale green space and land surface temperature in Dalian is significant, showing a centralized and contiguous spatial pattern, with a trapezoidal structure decreasing from north to south. (4) The spatial adaptation between the fractal and thermal environments of green spaces can be evaluated using the inconsistency index. The development quality of green space can be divided into three types: advanced, relative coordination, and lagged green spaces. Finally, this study proposes specific suggestions for the development of block-scale green spaces and thermal environment management in Dalian City. [ABSTRACT FROM AUTHOR]

Mining disturbance is the underlying cause of dynamic disasters such as coal-rock deformation, gas outbursts, and roof water inrush. Mining disturbance leads to damage in coal-rock structures and closely relates to stope cracks' distribution characteristics. Therefore, it is crucial to investigate the coupling effects of the stress field, damage field, and seepage field of coal. Firstly, we established a mechanical model considering the coupling effect of damage and elastoplasticity, which aimed to describe the softening process of coal-rock mechanical parameters and the mutation law of the permeability coefficient in the damage process. Next, we developed a pore-fracture fractal model of damaged coal. It was used to elucidate the inherent relationship between damage and pore-fracture characteristics in the process of coal-rock crushing. We then proposed a quantitative evaluation method for determining the permeability characteristics of coal under the influence of mining disturbances. Finally, a numerical simulation of damaged coal 's mechanical behavior and seepage characteristics under stress-seepage coupling was conducted. The development model's effectiveness was verified through comparison with experimental results. In summary, our research offered a solid scientific foundation for quantitative evaluation and accurate prediction of the evolution law of coal-rock permeability characteristics under the influence of mining disturbance. • Using Weibull failure and D-P criterion establishes the damage constitutive model. • Utilizing fractal theory to optimize the two-hole model's fracture system. • Verifying the accuracy of the coupled stress-seepage model via numerical simulation. • Investigating various conditions on the strength and permeability of coal. [ABSTRACT FROM AUTHOR]

Water scarcity affects all continents, with approximately 1.2 billion people living in areas where water is physically lacking. This scarcity is more accentuated in countries with an arid climate, and its impact becomes more threatening when the economy depends mainly on it. The Kingdom of Morocco, with its agricultural vocation, is one of them, especially in its southern regions. Therefore, mapping areas with high groundwater potential based on available geospatial data allows for optimizing the choice of a future well in such areas. Geometric average and fractal models were used to assess and delineate potential groundwater areas in the Tissent basin, Southeast Morocco. Eight factors, including topography, geology, hydrology, and hydrogeology, influencing the distribution of water resources was used. The formation permeability factor presents the most significant impact among the others, although it is directly related to most of them. The areas located in the central and downstream part of the basin are characterized by a high water potentiality due to increased geological formations' permeability near the drainage system, which constitutes a recharge zone, and a low slope allowing a prolonged water-formation contact time favoring a gradual infiltration of the water towards the deep aquifers. The groundwater potential map has been edited and validated by comparing it with data from 52 wells scattered throughout the basin. The favorable potential sectors cover 15.81% of the basin's total area. The moderate ones account for 21.36% while the unfavorable areas cover 62.83%. These results aim to provide policymakers and managers with a guide map for groundwater research and reduce hydrogeological investigation costs. [ABSTRACT FROM AUTHOR]

The relationship between temperature (T) and diversity is one of the most important issues in ecology. It provides a key direction not only for exploring the determinants of diversity's patterns, but also for understanding diversity's responses to climate change. Previous studies suggested that T–diversity relationships could be positive, negative, or unimodal. Although these studies accumulated many informative achievements, they might be unsatisfied due to (1) investigating inadequate range of T, (2) selecting incomplete diversity metrics, and (3) making insufficiently detailed analysis of correlation. In this study, species diversity is estimated by four most commonly used diversity metrics and three parameters of species abundance distribution (SAD), and two global datasets of marine phytoplankton (covering a wider range of T) are used to evaluate the T–diversity relationships according to a piecewise model. Results show that all aspects of diversity (except evenness) have the similar relationship with T in the range of lower T, noting that diversity significantly increases as T increases. However, in the range of higher T, diversity may significantly decrease or nearly constant, which indicates that their relationships may be the unimodal or asymptotic. The asymptotic relationship found by this study is assumed that increasing diversity with T will gradually approach the Zipf's law (1:1/2:1/3...). If such assumption can be verified by future investigations, the intrinsic mechanism of the asymptotic relationship is likely to be crucial in understanding the T–diversity relationships. [ABSTRACT FROM AUTHOR]

The physicochemical properties of "smart" or stimuli-sensitive amphiphilic copolymers can be modeled as a function of their environment. In special, pH-sensitive copolymers have practical applications in the biomedical field as drug delivery systems. Interactions between the structural units of any polymer-drug system imply mutual constraints at various scale resolutions and the nonlinearity is accepted as one of the most fundamental properties. The release kinetics, as a function of pH, of a model active principle, i.e., Curcumin, from nanomicelles obtained from amphiphilic pH-sensitive poly(2-vinylpyridine)-b-poly(ethylene oxide) (P2VP-b-PEO) tailor-made diblock copolymers was firstly studied by using the Rietger-Peppas equation. The value of the exponential coefficient, n, is around 0.5, generally suggesting a diffusion process, slightly disturbed in some cases. Moreover, the evaluation of the polymer-drug system's nonstationary dynamics was caried out through harmonic mapping from the usual space to the hyperbolic one. The kinetic model we developed, based on fractal theory, fits very well with the experimental data obtained for the release of Curcumin from the amphiphilic copolymer micelles in which it was encapsulated. This model is a variant of the classical kinetic models based on the formal kinetics of the process. [ABSTRACT FROM AUTHOR]

Cement emulsified asphalt mortar (CA) is widely used as the cushion of two types of ballastless track (CRTS I and CRTS II) in high-speed railways. Nowadays, the lack of durability of CA mortar has severely affected the quality of high-speed railways, failing to meet the requirements of sustainability. Since CA mortar is a kind of porous material, its performance can be significantly affected by its microstructures, which means that revealing the evolution law of its microstructures can provide the basis for improving its durability. Therefore, CA mortar species with different asphalt-cement ratio under different curing ages were prepared based on the requirements of CRTS II in this research and the pore structures were determined based on SEM and NMR methods. Then, a fractal model of CA mortar pore volume was proposed based on the concept of box fractal dimension, and the fractal dimension of pore volume was calculated. The relationship between fractal dimensions and mechanical property was analyzed based on Pearson correlation coefficient and regression analysis. The results suggested that the overall microstructure of CA mortar shows a loose porous space structure with cement hydration products being the continuous phase and asphalt being the dispersed phase. With the increase in A/C ratio, the hydration products produced by cement hydration decrease, and the total porosity and average porosity of CA mortar gradually increase due to the increase of asphalt hindering the hydration process of the cement. With the increase in curing age, the pore structure of CA mortar becomes more compact. However, the evolution law of CA mortar pore structure with age is not consistent under different A/C ratios due to the influence of asphalt. The pore structure of CA mortar was proved to have obvious fractal characteristics based on the concept of box fractal dimension and the experimental data of NMR. In addition, the correlation analysis proves that the fractal dimension of pore structure has an obvious positive correlation with the compressive and flexural strength, which suggests that the fractal dimension of pore volume can be a bridge for connecting the macro-property and micro-structures of CA mortar. [ABSTRACT FROM AUTHOR]

Mapping of geochemical anomalies is crucial to exploration and environmental geochemistry. The complex geochemical landscape, multiple geological sources and various secondary surficial processes impose a certain degree of spatial uncertainty in mapping of geochemical anomalies. Quantifying this uncertainty is significant for improving the efficiency of environmental monitoring or mineral prospecting. In this paper, sequential indicator simulation (SISIM) was used to assess local and spatial uncertainties of geochemical anomalies, and the concentration–area (C–A) fractal model was employed to determine the geochemical threshold prior to SISIM analysis. To illustrate the uncertainty of Ag geochemical anomalies, Ag concentration data of 1880 soil samples collected from NE of the Dong Ujimqin Banner district of Inner Mongolia, North China, was used in this study. Based on a set of simulation realizations of Ag concentrations, it was concluded that areas with low local (i.e. single-location) uncertainty of Ag concentrations entail low risk for mineral exploration. However, the spatial uncertainty for multi-locations showed that the joint probability statistics were stricter than local uncertainty. Therefore, combining local probability and spatial joint probability for delineating geochemical anomalies of Ag is more acceptable and reliable. The hybrid approach using the C–A fractal model and SISIM provides a new way to delineate anomalous areas by considering the uncertainty of spatial distributions of geochemical elements. Thematic collection: This article is part of the Applications of Innovations in Geochemical Data Analysis collection available at: https://www.lyellcollection.org/topic/collections/applications-of-innovations-in-geochemical-data-analysis [ABSTRACT FROM AUTHOR]

The relationships between the inorganic nutrients and diversity of dinoflagellate cysts (the N-Dc relationships) are one of the most central issues in coastal ecology. It is not only an important pathway to explore the ecological processes of plankton, but also a key element for assessing eutrophication in marine ecosystems. Although the N-Dc relationships have been studied for many years, they have remained controversial, which may be attributed to (1) using samples collected from a single source (2) considering an insufficient range of nutrient concentrations (3) rarely taking into account species abundance distributions (SAD) that could better represent diversity. In this study, the N-Dc relationships are evaluated according to a compiled dataset, which cover the wide range of nutrient concentrations. Species diversity of cysts are estimated by four common diversity metrics and a new SAD parameter. Results show that all diversity metrics are negative with nutrients, which supports that low diversity of cysts could be considered as a signal of eutrophication. Additionally, this study finds a new pattern that SAD of cysts (Nr/N1, Nr and N1 is the abundance of the r-th and the first species in descending order) with decreasing nutrients appears to gradually approach 1: 1/2: 1/3…. In the future, if this pattern can be verified by more investigations, understanding the negative N-Dc relationships is more likely to provide new direction for assessing and managing eutrophication in coastal ecosystem, and even for exploring the general mechanisms determining diversity.

The contact parameters of joint interfaces have a great influence on the dynamic performance of the machine tool, and the dynamic performance determines the machining precision of the machine tool. Therefore, it is important to accurately identify the contact parameters of joint interfaces to improve the machining precision of the machine tool. In this paper, a method of identifying the joint interface stiffness parameters based on a joint simulation in Matlab and Ansys is first proposed, and then stiffness parameters of joint interfaces between the bed and column of the precision grinding machine are identified by applying the method. Finally, the feasibility and high efficiency of the proposed method are proved by comparing the natural frequencies of the simulation and the experiment. In order to further analyze the influence of joint contact parameters on the performance of the joint interfaces, the theoretical model of the normal stiffness of the joint interfaces based on fractal geometry is amended and verified by taking into account the asperity interaction and elastic–plastic deformation. Then, the modified model is extended to a three-dimensional model, which is more in line with the actual situation. Finally, the influencing factors of the joint interface stiffness are analyzed. The conclusions of this paper are of great significance in the dynamic performance analysis and structural design of machine tools.

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Capillary pressure is a crucial input in reservoir simulation models. Generally, capillary pressure measurements are expensive and time-consuming; therefore, there is a limitation on the number of cores tested in the laboratory. Accordingly, numerous capillary pressure models have been suggested to match capillary pressure curves and overcome this limitation. This study developed a new fractal capillary pressure model by depicting the porous system as a bundle of tortuous triangular tubes. The model imitates the pores' angularity, providing a more accurate representation of the pore system than smooth circular openings. Moreover, triangular tubes allow the wetting phase to be retained in the tube's corners. A genetic algorithm was employed to match the capillary pressure curves and obtain the proposed model's parameters. Capillary pressure data of eight lowpermeability sandstone samples from the Khatatba formation in the Western Desert of Egypt were utilized to test the proposed model. The results revealed that the developed model reasonably matched the laboratory-measured data. [ABSTRACT FROM AUTHOR]

The fractal characteristics of soil particle-size distribution (PSD) constitute an important soil physical property, and fractal models of soil PSD are increasingly used to describe the effects of vegetation on the improvement of soil-related properties. Based on the fractal theory, this paper selected four typical vegetation restoration types (Quercus acutissima, QAC; Robinia pseudoacacia, RPL; Pinus densiflora, PDS; QAC × PDS) in the Taiyi mountainous area as the research object, and the single-fractal dimension (D) and multi-fractal parameters of PSD and its correlation with soil-associated properties were studied. The results show that (1) QAC × PDS reduced the heterogeneity of soil sand distribution, which also increased the range and concentration of soil PSD in the dense area. Soil clay and silt contents showed QAC × PDS > RPL > QAC > PDS. QAC × PDS significantly increased clay and silt content in 0–20 cm soil. (2) D varies among different vegetation restoration types, which was QAC × PDS > RPL > QAC > PDS, and the D of 0–20 cm soil was greater than that of 20–40 cm. For the multi-fractal parameters of PSD, the capacity dimension (D0), information dimension (D1), correlation dimension (D2) and D1/D0 in 0–20 cm soil of different vegetation restoration types showed significant differences. (3) D and multi-fractal parameters were significantly positively correlated with clay and silt contents, which were significantly negatively correlated with sand contents. (4) QAC × PDS had the smallest soil bulk density and largest porosity. Fractal dimension was negatively correlated with soil bulk density and positively correlated with soil total porosity and capillary porosity. These results indicate that the soil fractal dimension can well characterize the vegetation improvement on soil structure and properties in the earthy-rocky mountain areas of northern China. [ABSTRACT FROM AUTHOR]

• A fractal model for gas–water relative permeability in inorganic shale was proposed. • The complex water occurrence state in inorganic shale was considered. • The proposed model was validated by experimental data of shale and other porous rock. • How water occurrence state affects the gas–water relative permeability was revealed. • The impact of key factors on relative permeability in inorganic shale was explored. Gas-water relative permeability in inorganic shale plays a crucial role in fluid transfer efficiency, therefore it is of paramount importance for modelling shale gas recovery. This study introduces a novel theoretical model to determine gas–water relative permeability in inorganic shale under various water saturations. For the first time, this model integrates the water occurrence state in inorganic shale with the fractal characteristics of pore structures. In particular, three distinct states of water occurrence in inorganic shale pores and two corresponding critical pore sizes are defined in the model based on nuclear magnetic resonance (NMR) testing. The validity and accuracy of the new model have been corroborated by multiple sets of experimental data for shale and other porous rocks. Additionally, the model discussion focus on the water occurrence state in inorganic shale is conducted, and the following results are innovatively obtained: (1) Ignoring pores with only irreducible water results in a 6–26 % overestimation of gas relative permeability (GRP) and approximately 4 % overestimation of water relative permeability (WRP). (2) Omitting pores with both irreducible and movable water leads to a 2–13 % overestimation of GRP and a 1.1 to 21 times overestimation of WRP at various water saturations. (3) Disregarding pores with only movable water causes an approximately 23 % underestimation of GRP and a 13–100 % underestimation of WRP at different water saturations. Furthermore, based on the proposed model, the impact of fractal dimension of pore size distribution, fractal dimension of pore tortuosity, irreducible water saturation, and critical pore sizes are also comprehensively analyzed. [ABSTRACT FROM AUTHOR]

In this paper, we argue for the case that cities are self-organised complex systems by presenting evidence on positive and reinforcing feedback mechanisms and robust global trends that characterise historical growth patterns. In two case studies; Manhattan and Barcelona, historical stages of urban growth were mapped and analysed. The analyses revealed regularities that may help define the local and global processes that characterise urban growth marked by alternating periods of expansion and pruning in street networks. The global trend marked by a lognormal distribution of segmental integration (closeness) in street networks was consistently restored following planning interventions. The overall street network growth trend appeared to fit an exponential or power law distribution, along with a linear change in fractal dimension. Underlying these global trends, we found evidence for local positive and reinforcing feedback mechanisms; explained by preferential attachment to well-connected street structures, and pruning of weakly integrated local street structures. The findings are likely to improve our understanding of urban growth.

Horizontal drilling is the major method of shale gas extraction, and hydraulic fracturing improves the gas production effectively. However, as the main gas migration channel, shale microstructures, such as the natural fractures and pores, are extremely complicated, and it is difficult to characterize them quantitatively by conventional approaches. Besides, the microstructural evolution of the hydraulic fracture (HF) area is more intricate. In order to quantitatively characterize the evolution of shale microstructure after hydraulic fracturing, and to investigate the contribution to the gas extraction process, a fully coupled fractal thermal–hydrological–mechanical permeability model is proposed. And the interaction of shale microstructure, thermal–hydrological–mechanical effects, and gas permeability in the HF area is also quantitatively investigated. Shale thermal conduction, gas pressure, and adsorption–desorption effect are defined as functions of the effective stress responsible for shale matrix deformation, and operate directly on shale porosity, which induces changes in shale microstructure, including the shale fractal dimension (for characterizing the density of natural fractures in shale) and the maximum fracture length. Multiphysical effects have a major impact on gas seepage, and directly affecting the permeability. Furthermore, compared to the widely used cubic permeability model, this model is significantly superior in analyzing the permeability evolution in the hydraulically fractured area, and the reliability is verified by the production data from the Marcellus Shale. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nanoparticles have been applied to remediate heavy metal pollutants (e.g., arsenic) in groundwater and soil, where the migration mechanism of pollutants in this multi-component system has not been fully understood. To better understand how nano-iron oxide affects arsenic migration under multivariate influence, this study prepared arsenic loaded composite colloids using arsenic (As(V)), humic acid, and nano iron oxide (n-α-Fe2O3). Then we explored the migration behavior of the composite colloids (HA-n-α-Fe2O3) loaded As(V) in a quartz sand column affected by n-α-Fe2O3 under various humic acid concentrations, pH values, ionic strengths, and ferric oxide contents. Two migration models, including a classical advection-dispersion equation (ADE) and a Hausdorff fractal advection-dispersion equation (HADE), were used to quantify the observed co-migration of arsenic conveyed by HA-n-α-Fe2O3 colloids loaded As(V) in the column. Our analysis indicates that the adsorption capability of nano-iron oxide on arsenic decreases with pH, humic acid and iron oxide concentrations, thus accelerating arsenic movement. While, the increasement of ionic strength enhances the adsorption force of nano-iron oxide on arsenic and suppresses arsenic migration. Furthermore, simulation results suggest that the HADE model outperforms the traditional ADE model in characterizing arsenic migration, where the time derivative index is an indicator of anomalous diffusion.