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This work focuses on porosity formation during the welding of dissimilar aluminium alloys (cast and sheet) by pulsed gas metal arc welding (GMAW) with different travel speeds (12–14 mm/s) and by friction stir welding (FSW). The case study concerns the assembling of a battery-pack enclosure prototype. The welded specimens were scanned by 3D X-ray computed tomography. The cast base material (BM) shows a porosity percentage of 1.45%, and it is characterized by pores with a strong hyperbolic relationship between equivalent diameter and sphericity. Considering the GMAW beads, porosity rises with the travel speed (from 1.80 to 5.12%), due to the reduction of the opening window in which pores can escape. Pores with volume higher than 0.10 mm3 rise with the travel speed, representing from 9.75 to 32.98% of the total porosity. These pores are responsible for the weaker hyperbolic connection for sphericity found for the GMAW beads. On the other hand, FSW mixes and homogenizes the pores in the cast BM. The novelty of the paper lays in proving the strong potentialities of FSW for weld porosity reduction. A re-designing of the battery-pack enclosures is necessary to limit arc welding in marginal areas, which are not crucial for sealing but necessary to create a stable platform to be subsequently sealed with FSW. [ABSTRACT FROM AUTHOR]

Nickel-titanium shape memory alloy is a novel material with outstanding properties suitable for biomedical applications such as implantation devices. Unfortunately, the high composition of nickel in this alloy can be harmful to the human body, if its exposure exceeds a threshold value. Therefore, an innovative electrical discharge coating technique was investigated and proposed in this study to develop minimal microdefect formation with high corrosion resistance through fractional factorial design of experiment. The results showed that discharge duration mostly dominated the material deposition, microcracks, and porosity fraction up to 72%, due to the impact of the intensity of discharge energy. There was also a pronounced effect of titanium powder concentration in the deionized water on the percentage of titanium and nickel elements and microcrack formation. The powder suspension enhanced the recast layer formation through the increment of layer density, which covered up the Ni-rich region and diminished the microcrack formation. An optimized substrate recorded the lowest corrosion current, I corr , and highest corrosion voltage, E corr , at 3.43 × 10 - 6 µA/cm2 and − 0.07 V respectively, thus exhibiting an outstanding corrosion resistance rate at only 8.57 µm/year in phosphate-buffered saline solution, due to the low nickel concentration, low microcracks, and low porosity fraction in the recast layer. Therefore, the results obtained within this styud presented an initial step towards assessing the feasibility of applying the electrodischarge process to biomaterials, including nickel-titanium shape memory alloy. Further exploration, involving both in-vitro and/ or in-vivo studies, is essential to thoroughly evaluate the performance of the coating obtained from the process. [ABSTRACT FROM AUTHOR]

In glass industry, the evolved gases and fumes from burning the gas fuel absorbed in calcium hydroxide to minimize the pollution of environment. After a period of time, the calcium hydroxide fouled with sulphate and carbonate as action of the absorbed SO3 and CO2 gases. Based on our interest to treatment the solid waste materials, this study intended to convert the obtained waste of calcium hydroxide fouled with gases to valuable products. Firstly, this waste was treated with water, caustic soda and acids. The results confirmed the conversion of waste to pure calcium sulfate by treatment with 6 v/v% sulfuric acid. Secondly, the obtained calcium sulfate was reacted with ammonium dihydrogen phosphate solution for preparation of calcium hydroxyapatite (HAp) nanoparticles. The produced HAp sample was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and N2 adsorption measurements. The obtained findings confirmed that the HAp can be produced after calcination at 700 °C, nanorods-like of sizes ranged from 11 to 15 nm and with main surface functional groups of hydroxyapatite. TGA and DTA data indicated that HAp is thermally stable up to 700 °C. Also, the obtained HAp has Ca/P molar ratio of 1.60 and exhibited high total surface area of 146 m2/g with mesoporous structure which make this material can be used in medical and water purification applications. [ABSTRACT FROM AUTHOR]

Extensive usage of pervious concrete (PC) in pavement applications to mitigate the shortcomings in conventional impervious paving is on the rise. The primary performance parameters of PC are strength and porosity which greatly depend on aggregate grading and shape of the constituents, aggregate to cement (A/C) ratio, water to cement (W/C) ratio, and compaction effort. This paper discusses the development of a model to predict compressive strength of PC using compaction effort and A/C ratio and. For compaction effort of 0–90 blows and A/C ratios of 2.5–4.0, the proposed model perfectly predicted the compressive strengths of PCs in the range of 3.0–30.0 MPa. The mean deviation and mean relative error of the estimated compressive strengths were 1 MPa and 10%, respectively. Findings of this study could contribute in choosing the right A/C ratio and compaction effort for mix design of PC. Noticeably, strength requirements of typical pavement applications exist in the same range as the developed model predictions lie in, which guarantee the application of proposed model for transport infrastructure development but not limited to. Further extension of the proposed model is feasible by incorporating the effect of aggregate grading and shape on compressive strength. [ABSTRACT FROM AUTHOR]

This paper presents an analytical formulation to investigate functionally graded porous beams' nonlinear thermal buckling performance under various boundary conditions. The current model incorporates innovative cinematic techniques with the focus on the stretching effect and the iteration techniques. The material properties of the porous FG beams are temperature-dependent and vary according to a simple power-law distribution. The validity of the present theory' results is confirmed by comparing them with those obtained by other researchers. The findings demonstrate that the critical buckling temperature in TD and TID ranges from 1.03 to 1.27% for a uniform distribution and 1 to 1.47% for linear and non-linear distributions. Conversely, for regular porosity variation, the critical buckling temperatures fluctuate between 0.99 and 1.74%, and between 0.99 and 1.59% for porosity variation. Furthermore, the influence of boundary conditions becomes more pronounced when the nonlinear temperature difference is high. [ABSTRACT FROM AUTHOR]

To investigate the characteristics of crack propagation and microscopic structure under water–rock coupling effect in deep surrounding rock, a triaxial mechanical experiment was conducted on sandstone strata in the Shandong Wanfu Coal Mine under the action of pressurized water absorption. The experimental results showed that the mass increment of the rock sample was exponentially related to the confining pressure, and the mathematical relationship curve of the mechanical strength variation of the rock sample under different confining pressures was obtained. Based on this, the strength softening formula of the rock sample with the absorption time under different confining pressures was obtained, and the softening process was divided into three stages: the relatively stable stage, the rapid softening stage and the deceleration softening stage. The T2 spectrum curve of the rock sample was normalized, and the pore distribution and strength softening curve under different confining pressures were constructed. The speed of water molecules entering pores in different softening stages was analyzed, and it was found that in the relatively stable stage, the speed was micro-pore > meso-pore > macro-pore, in the rapid softening stage, the speed was meso-pore > macro-pore > micro-pore, and in the deceleration softening stage, the speed was micro-pore ≈ meso-pore ≈ macro-pore. According to the law of microscopic pore structure changes under water–rock coupling, a pore structure model of sandstone under different confining pressures was constructed. Based on the crack propagation model and crack propagation rate formula, it was concluded that the increase in crack strain propagation rate was the result of both water saturation and permeation water pressure, and a distribution map of the crack strain propagation rate was established. By comparing the crack strain propagation rate, it was found that under the same characteristic stress, the axial strain propagation rate of the crack was greater than the radial strain propagation rate, and the radial strain propagation rate was greater than the volume strain propagation rate. Quantitative relationships between crack propagation in sandstone and water saturation under different stress conditions were obtained. [ABSTRACT FROM AUTHOR]

This current study provides a comprehensive examination of a novel method for studying the dynamics of a fractionalized Maxwell flow near an inclined plate, considering non-uniform mass transfer through a permeable media. Through the use of partial differential equations, incorporating heat and mass movement effects, the study employs a combination of generalized Fick’s and Fourier’s law with the Caputo operator. Transforming the fractionalized model into dimensionless form using appropriate dimensionless values, semi-analytical solutions for the non-dimensional transmitted fractional model are obtained via the Laplace transformation method. Through graphical analysis, the precise contributions of key parameters such as heat generation, radiation, and chemical reactions are elucidated, including their impacts on the calculated heat generation parameter (Qo), radiation parameter (Nr), and others. The study’s significance lies in its implications for the design of efficient heat exchangers, fluid flow systems, and cooling components in complex engineering systems, including nuclear reactors and power generation plants. Furthermore, the fractional derivative approach offers a more accurate representation of the viscoelastic behavior of materials like polymers, crucial for optimizing fabrication processes such as extrusion and molding. The insights gained from this study extend to the realm of miniaturized fluidic devices, including bio-analysis tools, lab-on-a-chip technology, and microfluidic drug delivery systems, where improved performance and control need a grasp of Maxwell fluid dynamics. The physical outcome of this research lays the groundwork for future investigations that will maximize heat transfer efficiency in real-world systems and give insightful information on the behavior of complicated fluids. We compute and display the skin friction, mass and heat transfer rate in tabular form. [ABSTRACT FROM AUTHOR]

In this study, Eringen's nonlocal elasticity theory that applies the small size effects in functionally graded porous nanotubes embedded in an elastic matrix is discussed. The material properties of functionally graded porous nanotubes are taken into account to vary over the radius direction with a rule of mixture. The free torsional vibration relation according to nonlocal elasticity theory, via Hamilton's principle, is obtained and an eigenvalue solution is constructed for the free torsional vibration response of the presented work. The presented analytical model is validated by comparing the calculated mathematical results for homogeneous nanotubes with rigid and non-rigid boundary conditions. Special attention is given to deformable boundary conditions, porosity coefficient, material grading coefficient and also to the influence of elastic medium on the free torsional vibration frequencies. In this paper, it has been proven that the influence of length, elastic medium, elastic torsional spring rigidities, material grading and porosity coefficients on the vary in the torsional vibration frequency of the functionally graded nanotube is not small. [ABSTRACT FROM AUTHOR]

Photocatalytic ethanol conversion into high-valuable chemicals while realizing hydrogen production is attractive and challenging. In this study, flower-like, porous flower-like, and net-like CdS nanostructures were prepared by solvothermal technique and were used to investigate the effect of morphology on ethanol conversion. It was found by characterization that the one-dimensional net-like CdS had the best crystallinity and the largest specific surface area, which provided more active sites and possessed superior ethanol conversion activity. The ethanol conversion was 4.7% in 10 h with a hydrogen production rate of 1.32 mmol g−1 h−1 and an acetaldehyde (AA) production rate of 1.96 mmol g−1 h−1 with a selectivity of 51%. In comparison, 2,3-butanediol(2,3-BDO) was produced at a rate of 0.61 mmol g−1 h−1 with a selectivity of 32%. The pore structure of one-dimensional net-like CdS with predominantly large mesopores showed better selectivity for 2,3-BDO, indicating that the pore size of the catalyst plays an important role in the C–C coupling reaction. Further, the catalysts were modified by depositing Pt nanoparticles on net-like CdS and the photocatalytic ethanol conversion performance was improved by about 3.5 times. [ABSTRACT FROM AUTHOR]

The laser separation distance (distance between the two lasers in welding direction) in double-sided laser beam oscillation filler welding is difficult to precisely control. To evaluate the effect of laser separation distance on the mechanical properties of T joints, 2219 aluminum alloy double-sided laser beam oscillation filler welding experiments with different laser separation distances were conducted in this work. With laser separation, the symmetry of fusion zone was weakened. The keyhole stability at latter welding side was weakened. The number of pores in the T joint increased. The laser separation distance promoted the formation of porosity at latter welding side and the formation of porosity in the stringer. Most of the cracks in the tensile tests at the weld foot propagated in the partially melted zone. Porosity has no significant influence on the tensile strength of T joints. When laser separation distance was 3 mm, the mechanical performance of T joint was the best. The hoop tensile strength was 370.0 MPa. The T-pull tensile strength was 309.5 MPa. Based on the results of tensile strength testing, the mechanical performance of T joints welded by double-sided laser beam oscillation filler welding did not deteriorate with the laser separation distance less than or equal to 3 mm, which showed a good tolerance of laser separation distance for the welding process. [ABSTRACT FROM AUTHOR]

The mechanical properties of rockfill materials are not only influenced by microscopic factors such as particle morphology and gradation, but also closely related to different loading stress paths. It is of great significance to study the microscopic mechanical properties of rockfill materials under different stress paths for revealing the macroscopic mechanical properties as well as the microscopic deformation and failure mechanisms of rockfill materials. In this paper, based on the results of triaxial tests, a series of numerical triaxial simulation tests under different stress paths were carried out using the discrete element particle flow method, and the deformation, strength change rules, and fine structure evolution mechanism under three stress paths were explored. The results demonstrated that there were significant differences in the effects of stress paths on the stress–strain and strain-volume change characteristics of the rockfill materials. Stress paths exhibited little effect on the strength characteristics. The anisotropy of strong contact number and strong contact force was the microscopic source of macroscopic strength. The contact situation between the particles was the main microscopic factor affecting the macroscopic deformation. The intrinsic mechanism of macroscopic deformation properties could be revealed by the average coordination number and porosity. The stress path affected the growth rate of the number of bond failures and the total number of failures. The relationship between macroscopic mechanical properties and microstructural evolution under different stress paths was also discussed. The findings can provide meaningful insights into the deformation control and stability analysis of rockfill engineering. [ABSTRACT FROM AUTHOR]

To explore the spontaneous combustion characteristics and hazards of the low-temperature oxidation (LTO) stage in the process of spontaneous combustion of coal and mudstone, the pore structure, spontaneous combustion characteristic parameters, and exothermic characteristics of coal and mudstone were tested and studied, and the oxidation kinetic parameters were calculated. The results show that mudstone has a larger specific surface area and pore volume than coal. From the fractal characteristics, the pore structure of mudstone is more complex than that of coal. According to the comparison of theoretical and actual gas generation and oxygen consumption rate curves, it is found that there is an interaction between coal and mudstone in the LTO process. With the increase of mudstone mass ratio, gas production, and its oxygen consumption rate increase. Among them, CM-4 (Coal:Mudstone = 1:1) has the highest exothermic intensity and the exothermic factor (A) and fire coefficient (K) increase with the increase of mudstone content. The apparent activation energy of the mudstone sample is lower than that of the raw coal, indicating that the sample after adding mudstone is more likely to have spontaneous combustion in the LTO stage. [ABSTRACT FROM AUTHOR]

Moderate-to-profound sensorineural hearing loss in humans is treatable by electrically stimulating the auditory nerve (AN) with a cochlear implant (CI). In the cochlea, the modiolus presents a porous bony interface between the CI electrode and the AN. New bone growth caused by the presence of the CI electrode or neural degeneration inflicted by ageing or otological diseases might change the effective porosity of the modiolus and, thereby, alter its electrical material properties. Using a volume conductor description of the cochlea, with the aid of a 'mapped conductivity' method and an ad-hoc 'regionally kinetic' equation system, we show that even a slight variation in modiolus porosity or pore distribution can disproportionately affect AN stimulation. Hence, because of porosity changes, an inconsistent CI performance might occur if neural degeneration or new bone growth progress after implantation. Appropriate electrical material properties in accordance with modiolar morphology and pathology should be considered in patient-specific studies. The present first-of-its-kind in-silico study advocates for contextual experimental studies to further explore the utility of modiolus porous morphology in optimising the CI outcome. [ABSTRACT FROM AUTHOR]

Monoculture switchgrass and restored prairie are promising perennial feedstock sources for bioenergy production on the lands unsuitable for conventional agriculture. Such lands often display contrasting topography that influences soil characteristics and interactions between plant growth and soil C gains. This study aimed at elucidating the influences of topography and plant systems on the fate of C originated from switchgrass plants and on its relationships with soil pore characteristics. For that, switchgrass plants were grown in intact soil cores collected from two contrasting topographies, namely steep slopes and topographical depressions, in the fields in multi-year monoculture switchgrass and restored prairie vegetation. The 13C pulse labeling allowed tracing the C of switchgrass origin, which X-ray computed micro-tomography enabled in-detail characterization of soil pore structure. In eroded slopes, the differences between the monoculture switchgrass and prairie in terms of total and microbial biomass C were greater than those in topographical depressions. While new switchgrass increased the CO2 emission in depressions, it did not significantly affect the CO2 emission in slopes. Pores of 18–90 µm Ø facilitated the accumulation of new C in soil, while > 150 µm Ø pores enhanced the mineralization of the new C. These findings suggest that polyculture prairie located in slopes can be particularly beneficial in facilitating soil C accrual and reduce C losses as CO2. [ABSTRACT FROM AUTHOR]

In this study, a method is demonstrated for predicting defect-laden areas within deposits produced by cold spray additive manufacturing that are caused by substrate geometry and robot tool path. Leading edge shapes were used as the test bed for this method, and porosity was selected as the metric by which defects are quantified. A porosity model was developed based on the observation that porosity is significantly influenced by particle impact velocity normal to the surface and is therefore highly correlated to particle impact angle. The model outputs deposit shape and a probability map of porosity based on initial substrate geometry and robot tool path as inputs. The model was calibrated by experimental deposits formed at varying impact angles. To validate the method, the model was applied to three airfoil leading edge geometries and was shown to qualitatively estimate the density of pores in the deposit. The study also revealed that robotics alignment is an important factor in causing defects within highly curved geometries. The mathematical construct of the model is applicable to other applications outside of leading edges and deposit properties beyond porosity, but other applications and properties are not evaluated in this study. [ABSTRACT FROM AUTHOR]

Pressurized water reactors are designed to operate in a single-phase flow. However, during a flow loss or other off-design conditions liquid temperature may exceed saturation temperature and, if a continuous film of gas forms, a boiling casualty may result. If superhydrophobic surfaces are introduced among the fuel cell assembly, vapor bubbles show an affinity to these surfaces and gas may coalesce to escape faster, resulting in a larger margin to reach critical heat flux. In the present study, we consider air and liquid water mixture examining the overall flow dynamics in a case with no bulk liquid flow, reminiscent of a case with coolant pump failure. The parameter ranges examined span Reynolds number based on gas superficial velocity up to 5300 and produced bubble with bond numbers from 1 to 270, and Weber numbers based on estimated terminal velocity from 0.6 to 150. The Morton number was fixed at 2.63 × 10 - 11 . As the flow with high gas volume fraction becomes optically opaque and is sensitive to intrusive instrumentation, a custom-built photon-counting dual energy threshold X-ray computed tomography system is employed for measurement of the time average void fraction within the bundle non-intrusively. Two dual plane wire mesh sensors upstream and downstream of the rod bundle are employed to obtain comparison void fraction, velocity profiles and bubble size distributions. Additionally, traditional pressure-based gas holdup measurements are employed to calculate time- and volume-averaged void fraction. The data show that the presence of superhydrophobic surface being present in the rod bundle results in a significantly lower gas volume fraction and higher localized void fraction at the superhydrophobic coating, as compared to those in a similar rod bundle without superhydrophobic internals. [ABSTRACT FROM AUTHOR]

A numerical investigation of the influence of porosity, pore size, and planar defects (microcracks) on the elastic constants, compressive and tensile strength of a fine-grained matrix in a SiO2 refractory ceramics is presented. The modeling results show a qualitatively different effect of the 3D (pores) and 2D (microcracks) defects on its effective elastic properties. An increase in porosity leads to a decrease in Young's modulus and the strength of the refractory matrix, while the trend in the Poisson's ratio behavior depends on the degree of pore structure connectivity. Microcracks also reduce the effective strength and Young's modulus of the matrix but, unlike the pores, they cause an asymmetry in the effective elastic properties. The Young's modulus of the matrix decreases more slowly under compression than under tension, and the Poisson's ratio trend is the opposite (an increase under compression and a decrease under tension). The quantitative estimates of the effective mechanical characteristics of the fine grain matrix can be used in multiscale computer models of traditional and advanced SiO2-based refractories. [ABSTRACT FROM AUTHOR]

The tight tuff reservoir is an unusual type of unconventional reservoir with strong heterogeneity. However, there is a lack of research on the microscopic pore structure that causes the heterogeneity of tuff reservoirs. Using the Chang 7 Formation in Ordos Basin, China as a case study, carbon-dioxide gas adsorption, nitrogen gas adsorption and high-pressure mercury injection are integrated to investigate the multi-scale pore structure characteristics of tuff reservoirs. Meanwhile, the fractal dimension is introduced to characterize the complexity of pore structure in tuff reservoirs. By this multi-experimental method, the quantitative characterizations of the full-range pore size distribution of four tuff types were obtained and compared in the size ranges of micropores, mesopores and macropores. Fractal dimension curves derived from full-range pores are divided into six segments as D1, D2, D3, D4, D5 and D6 corresponding to fractal characteristics of micropores, smaller mesopores, larger mesopores, smaller macropores, medium macropores and larger macropores, respectively. The macropore volume, average macropore radius and fractal dimension D5 significantly control petrophysical properties. The larger macropore volume, average macropore radius and D5 correspond to favorable pore structure and good reservoir quality, which provides new indexes for the tuff reservoir evaluation. This study enriches the understanding of the heterogeneity of pore structures and contributes to unconventional oil and gas exploration and development. [ABSTRACT FROM AUTHOR]

Paleo-oil reservoir is of great importance to understand hydrocarbon enrichment mechanism and hydrocarbon exploration potential, but is yet poorly investigated in Kuqa Depression. The occurrence of the paleo-oil reservoir in Dabei area was proved by quantitative grain fluorescence (QGF) and fluid inclusion petrography. Development history of the paleo-oil reservoir was reconstructed through: (1) oil-source correlation; (2) time coupling of source rock maturation, porosity evolution and migration pathways. The impact of paleo-oil reservoir on tight-gas accumulation was consequently discussed. Results suggest that considerable oil was accumulated in the K1bs reservoir with paleo oil-water contact in Dabei 2 Well and Dabei 201 Well at 5 800 and 6 040 m, respectively. Crude oil was primarily sourced from Triassic source rocks with Jurassic source rocks of secondary importance, which was at oil generation window (0.7%–1.1% Ro) during 9–6 and 7.5–5 Ma, respectively. The occurrence of K1bs tight reservoir (porosity < 12%) was about 25 Ma, while faults and associated fractures at Kelasue structural belt were developed approximately from 8 to 3.5 Ma. Therefore, the tight oil accumulation was formed during 8–5 Ma. The paleo-oil reservoir in Dabei 1 gas field was destroyed by the evaporation fractionation in later stage. [ABSTRACT FROM AUTHOR]

Permeability of binary mixtures of soils is important for several industrial and engineering applications. Previous models for predicting the permeability of a binary mixture of soils were primarily developed from Kozeny–Carman equation with an empirical approach. The permeability is predicted based on an equivalent particle size of the two species. This study is aimed to develop a model using a more fundamental approach. Instead of an equivalent particle size, the permeability is predicted based on the bimodal void sizes of the binary mixture. Because the bimodal void sizes are not available as commonly measured physical properties. We first develop an analytical method that has the capability of predicting the bimodal void sizes of a binary mixture. A permeability model is then developed based on the bimodal void sizes of the binary mixture. The developed permeability model is evaluated by comparing the predicted and experimentally measured results for binary mixtures of glass beads, crush sand, and gravel sand. The findings can contribute to a better understanding of the important influence of pore structure on the prediction of permeability. [ABSTRACT FROM AUTHOR]

In the field of geotechnical engineering, many researchers have studied the disintegration of wet geotechnical bodies, but few have investigated the disintegration of sandy soils cured with water glass. In this study, the effects of modulus and Baume degree on the consolidation rate, particle size structure, pore size structure and gel state of sandy soils cured with water glass were investigated. The disintegration of cured specimens with different compositions was analyzed and discussed from the microscopic point of view. The results of the study show that the time required for consolidation of cured sandy soil decreased with increasing modulus and Baume degree. The Baume degree and modulus of sodium silicate affected the particle size and pore size structure of solidified soil. Due to differences in pore size and particle size structure, the disintegration of the specimens differed. For the samples with high Baume degree, their strength is high, but their water stability is poor, and the maximum disintegration degree is 95.72%. The sample with low Baume degree has low strength, but the water stability is good under the immersion condition, and the disintegration rate is less than 10%. The disintegration mechanism of solidified specimens was analyzed from the aspects of particle size, pore size structure and gel state. It is suitable to use water glass with high Baume degree in projects with dry environment and requiring high strength, while water glass with low Baume degree can be used for curing in wet environment. [ABSTRACT FROM AUTHOR]

Rare earth resources in the weathered crust elution-deposited rare earth ore (WCEDRE-ore) are mainly recovered by in situ leaching process. A new understanding of the engineering properties modification of WCEDRE-ore as well as the occurring microscopic mechanism was presented when leaching using ammonium sulfate agent occurred. The soil–water chemical reactions in leaching had a significant impact on engineering properties (such as permeability and strength) of WCEDRE-ore, which determined the success or failure of in situ leaching process. To reveal the internal processes and effects of ammonium sulfate leaching on WCEDRE-ore, indoor tests including leaching tests, chemical analyses, triaxial tests and nuclear magnetic resonance (NMR) tests were conducted. The results show that: (1) Under the action of ion exchange and seepage, the dispersion, deposition and clogging of fine particles occurred repeatedly and alternately along the seepage direction. (2) During the leaching process, the total porosity of the ore samples rarely changed, but the migration of fine particles leads to the transformation of micropores, mesopores and macropores in weathered-ore soil samples as well as the change of pore connectivity. As a result, the permeability coefficient of the tested soil samples decreased significantly at the beginning of test and then rose slightly. (3) Increased salt content during the leaching process enhanced soil cementation and structure until the end of ion exchange. However, owing to the loose pore structure in the upper part of sample and the dense pore structure in the lower part of the tested specimen generated by particle migration, the strength of soil sample was weakened, which was conducive to the occurrence of shear failure in the upper part of sample. [ABSTRACT FROM AUTHOR]

Porosity is the culprit for a large fraction of scrap in cast iron foundries, resulting in significant environmental and productivity losses. The present work focuses on characterizing and explaining porosity defects in industrial compacted and nodular graphite cast iron components, utilizing current literature for reference. The goal is to identify existing knowledge gaps in the field, fostering further research work. Complex-shaped castings were sampled from three foundries, weighing between 100 and 300 kg. These were carefully selected to capture recurring defects during stable production. The mechanisms behind these defects were discussed, and the findings were compared to the literature. Scanning electron microscopy (SEM) was used to investigate the inner surfaces of the pores with secondary electron imaging. The surrounding microstructure was captured with optical microscopy in combination with image analysis, where panoramic images and nodularity maps were built. Ultimately, etching based on Si segregation was employed. The results suggest that the understanding of pore surface film formation remains limited, particularly regarding graphite film formation. Notably, the observations reveal a multitude of previously unreported graphite structures within the pores, some with particles in their centers containing Ce, Ca, La and S. These novel structures can provide additional insights regarding pore formation chronology. [ABSTRACT FROM AUTHOR]

Shrinkage porosity is one of the most common defects leading to rejection in high-pressure die-casting (HPDC). As the metal solidifies, it contracts and shrinks in volume. If the cooling rate is too rapid or the metal is not sufficiently fluid, the shrinkage rate can exceed the rate of metal flow into the cavity, resulting in the formation of porosity. Shrinkage porosity appears as a network of small voids or pores, which can reduce the strength and integrity of the final product. This study aims to investigate the comparative effects of process parameters on shrinkage defects in HPDC. Our methodology focuses on examining four distinct casting models under various casting conditions, such as changes in molten metal injection temperature, injection speed. Despite the identified influence of these process parameters, it was observed that the part geometry plays a significant role in dictating the degree of shrinkage. While our results validate the effects of process parameters on shrinkage defects, it demonstrates the predominant role of the casting geometry. We employ the secondary dendrite arm spacing and dimensionless Niyama criteria for predicting shrinkage defects, verifying our simulation data with empirical evidence from an in-process-embedding sensor-equipped casting machine. The results reveal a clear correlation between the processing parameters and shrinkage once a specific geometry is established. Within a given geometry, the extent of shrinkage defects follows a pattern determined by the processing conditions. [ABSTRACT FROM AUTHOR]

Digital rock physics is based on imaging, segmentation and numerical computations of rock samples. Due to challenges regarding the handling of a large 3-dimensional (3D) sample, 2D algorithms have always been attractive. However, in 2D algorithms, the efficiency of the pore structures in the third direction of the generated 3D sample is always questionable. We used four individually captured µCT-images of a given Berea sandstone with different resolutions (12.922, 9.499, 5.775, and 3.436 µm) to evaluate the super-resolution 3D images generated by multistep Super Resolution Double-U-Net (SRDUN), a 2D algorithm. Results show that unrealistic features form in the third direction due to section-wise reconstruction of 2D images. To overcome this issue, we suggest to generate three 3D samples using SRDUN in different directions and then to use one of two strategies: compute the average sample (reconstruction by averaging) or segment one-directional samples and combine them together (binary combination). We numerically compute rock physical properties (porosity, connected porosity, P- and S-wave velocity, permeability and formation factor) to evaluate these models. Results reveal that compared to one-directional samples, harmonic averaging leads to a sample with more similar properties to the original sample. On the other hand, rock physics trends can be calculated using a binary combination strategy by generating low, medium and high porosity samples. These trends are compatible with the properties obtained from one-directional and averaged samples as long as the scale difference between the input and output images of SRDUN is small enough (less than about 3 in our case). By increasing the scale difference, more dispersed results are obtained. [ABSTRACT FROM AUTHOR]

The sandy conglomerate reservoir in layer Es3 of the Liaohe Eastern Depression has good potential for oil reservoir exploration and has been identified as a key area for future exploration. The low porosity and permeability, complex lithology, and strong heterogeneity of the target layer make it difficult to predict favorable reservoirs. The objective of this study is to analyze and process conventional logging data to extract feature parameters that affect lithology by establishing a decision tree lithology classifier. Principal component analysis is used to reduce data dimensionality, and the elbow method is applied to the clustering algorithm to establish the optimal number of clusters for the automatic classification of reservoir types. Further, support vector machines are used for lithology classification based on features with higher classification capabilities. The results show that the support vector machine lithology recognition method based on feature selection achieved an accuracy of 91.8%. The processing of actual well data has verified the feasibility of the method. Based on the combination of core experiments and oil testing results, the characteristics of three types of reservoirs were presented, and potential reservoir zones were proposed for drilling wells. The comprehensive analysis and the practical application of the developed method reveal that the class I reservoir has high hydrocarbon production and could be the most favorable reservoir in the Es3 sandy conglomerate. The processing data of lithology identification and reservoir classification evaluation are consistent with core data and hydrocarbon production data, verifying the effectiveness and practicability of the method proposed in this paper. The results of this study will serve as a reference for low porosity and permeability sandy conglomerate reservoir evaluation based on machine learning in the target area. [ABSTRACT FROM AUTHOR]

Amidst intensifying global agricultural water demand, optimizing management practices and understanding the role of soil amendments, particularly biochar (BC), in modulating soil water dynamics are critical. Here, we review the potential impacts of BC on soil water dynamics, elucidate mechanistic underpinnings, and identify critical research gaps and prospective avenues. In general, BC modifies soil structure, hydraulic properties, surface albedo, and heat fluxes, which influence soil water storage, energy balance, and irrigation paradigms. Depending on soil texture and BC properties, BC demonstrates a greater reduction in bulk density and saturated hydraulic conductivity in coarse-textured soils compared to fine-textured soils. BC application generally increases water holding capacity (WHC) while exhibiting no consistent impact on soil water infiltration. Increased WHC of soils results from increased porosity, surface area, and soil aggregation. Increased porosity arises from a confluence of factors, encompassing new pores formation, reorganization of pores, increased soil aggregation, dilution effects of BC, reduced soil compaction, and biotic interactions, including increased population of burrowing invertebrates. BC tends to increase plant-available water in coarser soils, attributed to its hydrophilic nature, augmented specific surface area, and enhanced overall porosity. However, BC may induce soil water repellency, contingent upon variables such as feedstock composition, pyrolysis temperature, and specific soil attributes. While BC exhibits transformative potential in enhancing soil hydraulic properties, scalability concerns and economic viability pose challenges to its widespread agricultural application. Overall, BC offers promising avenues for sustainable water management. However, it is imperative to explore large-scale applications and conduct long-term field studies across different management, climate, and soil types to fully understand how different types of BC impact soil water dynamics. Highlights: Biochar generally improves soil water retention in coarse-textured soils. In coarse-textured soils, biochar increases porosity and PAW but decreases bulk density and Ksat. The effects of biochar on infiltration rates vary depending on soil types, as well as biochar particle size, production temperature, and depth of placement. Further studies on the mechanisms governing water retention in biochar-amended soils are warranted. Long-term studies encompassing various soil and biochar types are necessary. [ABSTRACT FROM AUTHOR]

Electric arc furnace slag (EAF) and sandstone waste (SW) are two of the most abundantly generated industrial wastes whose utilization as precursors and supplementary cementitious materials has not been exhaustively studied. The current research study comprehensively investigates the effects of incorporating varying proportions (0–90%) of re-melted EAF as a co-additive on the engineering properties of elevated (80 °C) and ambient (30 °C) cured alkali-activated SW-based binders. Extensive laboratory tests were conducted to assess the physio-mechanical and durability performance of the resulting alkali-activated materials (AAM). Detailed mineralogical and microstructural characterization of SW, EAF, and alkali-activated samples was carried out using sophisticated analytical techniques. Results advocated that irrespective of the curing temperatures, SW-based AAM showed improved setting behavior, compressive strength, water absorption, and porosity characteristics with the increment of EAF at all substitution levels due to the concomitant development of CASH-CSH-NASH gel phases. Overall, it can be inferred that EAFs as a pozzolanic material successfully augmented the properties of SW-based alkali-activated binders, providing an efficient solution for disposal and negative environmental impacts associated with industrial wastes. [ABSTRACT FROM AUTHOR]

The primary objective of this paper is to develop an appropriate predictive formula for the compressive strength of pervious concrete, which depends on its mixture. This will allow for the improvement of the proportioning procedure that considers both the target porosity and target compressive strength. To achieve this, an effective computational strategy is first constructed and investigated for the creation of simple and easily applicable symbolic regression functions within the Genetic Programming-based Symbolic Regression framework. Recent advancements in fast logical parallelism and model-based algorithms are also applied to perform calculations on a large quantity of examples, with the aim of finding the most suitable analytical solutions at a low computational cost. Next, to assess the effectiveness of this model in predicting the compressive strength of concrete in general, computations are carried out using the well-known Yeh's dataset on conventional concrete compressive strength. This dataset has been extensively studied using both "black-box" and "white-box" machine learning algorithms. The results reveal that more suitable formulas can be generated through this computational process, compared to several scenarios discussed in the literature. Furthermore, the model is extended to pervious concrete, based on the dataset of 164 samples of 28-day compressive strength collected from 14 different sources. The findings for pervious concrete exhibited high accuracy compared to the most effective black-box models and micromechanical/empirical models, with a coefficient of determination of approximately 0.9 for simple predictive equations, thereby supporting the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Fused filament fabrication (FFF) is a widely used additive manufacturing process for producing functional components and prototypes. The FFF process involves depositing melted material layer-by-layer to build up 3D physical parts. The quality of the final product depends on several factors, including the component density and tensile strength, which are typically determined through destructive testing methods. X-ray microtomography (XCT) can be used to investigate the pore sizes and distribution. These approaches are time-consuming, costly, and wasteful, making it unsuitable for high-volume manufacturing. In this paper, a new method for non-destructive determination of component density and estimation of the tensile strength in FFF processes is proposed. This method involves the use of gradual error detection by sensors and convolutional neural networks. To validate this approach, a series of experiments has been conducted. Component density and tensile strength of the printed specimens with varying extrusion factor were measured using traditional destructive testing methods and XCT. The cumulative error detection method was used to predict the same properties without destroying the specimens. The predicted values were then compared with the measured values, and it was observed that the method accurately predicted the component density and tensile strength of the tested parts. This approach has several advantages over traditional destructive testing methods. The method is faster, cheaper, and more environmentally friendly since it does not require the destruction of the product. Moreover, it facilitates the testing of each individual part instead of assuming the same properties for components from one series. Additionally, it can provide real-time feedback on the quality of the product during the manufacturing process, allowing for adjustments to be made as needed. The advancement of this approach points toward a future trend in non-destructive testing methodologies, potentially revolutionizing quality assurance processes not only for consumer goods but various industries such as electronics or automotive industry. Moreover, its broader applications extend beyond FFF to encompass other additive manufacturing techniques such as selective laser sintering (SLS), or electron beam melting (EBM). A comparison between the old destructive testing methods and this innovative non-destructive approach underscores the possible fundamental change toward more efficient and sustainable manufacturing practices. This approach has the potential to significantly reduce the time and cost associated with traditional destructive testing methods while ensuring the quality of FFF-manufactured products. [ABSTRACT FROM AUTHOR]

The porosity and permeability characteristics of loess are crucial in studying the soil stability of loess strata. In this paper, porosity and permeability were analyzed by nuclear magnetic resonance (NMR) tests using soils from different depths of loess strata in the same section in the Fugu area. The results show a range in the soil porosity of 15.092~5.190%, with an overall decreasing trend with the increase in depth. The change trend of soil permeability is similar to that of soil porosity. The permeability changes from 0.612 to 0.011 md, and gradually decreases with the increase of depth. The change in porosity is also prominent in the layer with significant permeability changes. Micropores predominate in the loess layer’s pore structure during the loess layer’s compaction process, and the permeability falls as the number of micropores rises. Calcareous nodules are more likely to form in layers with significant permeability changes. The findings of this study have significance in the engineering construction of loess strata in the Loess Plateau area. [ABSTRACT FROM AUTHOR]

In this paper, Polyethylene Terephthalate Glycol (PETG) has been used as a novel thermoplastic thermo-responsive Shape Memory Polymer (SMP) with biocompatibility, excellent printability, cost efficiency, and transparency for the 3D/4D printing of porous structures by material extrusion. The high deformability of PETG allows for programming without an increase in temperature or the need for additional operations. This enabled the use of PETG for the Cold Programming (CP) of ordered porous shape memory structures, made possible by material extrusion printing technology. The porous samples were printed employing three patterns and two porosity percentages. The programming operation was performed at ambient temperature by applying different amounts of pre-strains under constrained and unconstrained compression modes. The constrained test was conducted using a mandrel and a matrix for exerting pure volume reduction (pure packing). The shape recovery test was accomplished above the glass transition temperature (Tg), and the fixity and recovery ratios were recorded. Employing 3D printing provided the ability to manufacture porous thermoplastic SMP structures with highly controllable pores geometry and sizes for different porosity percentages. The results showed that the combination of the uniform strain distribution in the porous structures with the help of the 3D printing process and CP on the new PETG SMP makes it possible to achieve high deformation in the glassy region, resulting in a complete shape recovery for two lozenge and vertical patterns. Among all specimens, constrained specimens by horizontal pattern had the highest fixity ratio of 90.7%. However, low fixity ratios in CP can be justified considering the existence of two stages of spring-back and structural relaxation after unloading, resulting from the elastic and viscoelastic behavior. Increasing Infill Density (ID) along with the constrained test (pure packing) improved the shape fixity. The existence of higher mechanical constraints and harsher localized deformation are speculated to be the case for this observation. Applying higher deformations (40 to 80%), for both designed tests, brought about a weakness in the shape memory performance, while it improved for 100% volume reduction. [ABSTRACT FROM AUTHOR]

The high geothermal environment causes a temperature gradient inside shotcrete, which affects the development of its mechanical strength. This research investigated the strength evolution of shotcrete in simulated high geothermal environment by applying a unidirectional heat source. The influence of temperature gradient on the pore structure, morphology, phase composition, and hydration degree of shotcrete was also studied. It was found that the early strength of shotcrete was improved but that the later strength was reduced in the high geothermal environment. It was attributed to the increase in harmful porosity and total porosity of the concrete caused by the high-temperature curing. Cracks and pores can be observed in the microstructure near the heat source region. Besides, the ettringite content in shotcrete was lower than that under standard curing environment and presented gradient distribution in the direction of the temperature gradient. [ABSTRACT FROM AUTHOR]

This study explores the effects of porosity as well as nonlocal parameter on both low- and high-frequency free vibration behaviors of functionally graded nanoplates for the first times. Three distinct models are used to describe porosity distribution. A combination of the six-unknown quasi-3D theory is utilized to define the displacement field of the nanoplates. The Hamilton's principle is exploited in combination with the nonlocal elasticity theory to establish the governing equations of the motion of the functionally graded nanoplates. The influence of some parameters such as geometric, power-law index, porosity, and nonlocal parameter on the free vibration behaviors of the functionally graded porous nanoplates is explored in detail. This pioneering study unveils a wealth of numerical findings that, for the first time, shed light on the intricate high-frequency behaviors exhibited by these nanoplates. These insights not only expand the scientific understanding of functionally graded porous nanoplates but also offer valuable knowledge that can empower scientists and engineers in their pursuit of designing and optimizing nanostructures in this domain. This research marks a significant milestone in the study of nanoplates, bridging the gap between low- and high-frequency vibration analyses and opening new avenues for future research and practical applications. [ABSTRACT FROM AUTHOR]

Porosity, as one of the reservoir properties, is an important parameter to numerous studies, i.e., the reservoir's oil/gas volume estimation or even the storage capacity measurement in the Carbon Capture Storage (CCS) project. However, an approach to estimate porosity using elastic property from the inversion propagates its error, affecting the result's accuracy. On the other hand, direct estimation from seismic data is another approach to estimating porosity, but it poses a high non-linear problem. Thus, we propose the non-parametric machine learning approach, Gaussian Process (GP), which draws distribution over the function to solve the high non-linear problem between seismic data with porosity and quantify the prediction uncertainty simultaneously. With the help of Random Forest (RF) as the feature selection method, the GP predictions show excellent results in the blind test, a well that is completely removed from the training data, and comparison with other machine learning models. The uncertainty, standard deviation from GP prediction, can act as a quantitative evaluation of the prediction result. Moreover, we generate a new attribute based on the quartile of the standard deviation to delineate the anomaly zones. High anomaly zones are highlighted and associated with high porosity from GP and low inverted P-impedance from inversion results. Thus, applying the GP using seismic data shows its potential to characterize the reservoir property spatially, and the uncertainty offers insights into quantitative and qualitative evaluation for hydrocarbon exploration and development. [ABSTRACT FROM AUTHOR]

Understanding the mechanical properties and porosity of reproductive tissues is vital for regenerative medicine and tissue engineering. This study investigated the changes in Young's modulus (YM), storage modulus (E′), loss modulus (Eʺ), and porosity of native and decellularized bovine reproductive tissues during the estrous cycle. Testis tunica albuginea had significantly higher YM, E′, and Eʺ than the inner testis, indicating greater stiffness and viscoelasticity. Endometrium showed no distinct differences in YM, E′, or Eʺ across the estrous cycle or between horns. Ovaries exhibited significant variations in YM, E′, Eʺ, and porosity, with higher YM and E′ in the ipsilateral cortex and medulla during the luteal phase. Decellularized ovarian tissues displayed increased porosity. The oviduct displayed no significant differences in YM or E′ in the isthmus, but the contralateral ampulla had reduced YM and E′ in the luteal phase. These findings offer valuable insights into the dynamic mechanical properties and porosity of reproductive tissues, facilitating the development of biomimetic scaffolds for tissue engineering applications. [ABSTRACT FROM AUTHOR]

The emergence of innovative high-performance stainless steels is essential at the forefront of material science. This research highlights the meticulous development of a novel high-Mn-N Ni-free austenitic stainless steel via the powder bed fusion laser–based (PBF-LB) technique. We strategically optimized the laser parameters, achieving ultralow porosity and a refined microstructure with defects under 2%. Comprehensive analysis revealed superior dendritic cellular formations at melt pool boundaries, underlining our method's precision. Unveiling the strength of this novel steel, sample S11 (scanning speed of 800 mm/s and laser power of 147 W) showed a remarkable tensile strength of 1190 ± 20 MPa and an impressive elongation to fracture of 35 ± 3%. Interestingly, twin formations became evident under external loads, enhancing mechanical resistance while preserving ductility. Advanced quantification methods were employed to ensure accuracy, especially for low atomic number elements, overcoming previous measurement constraints. This pioneering study introduces a game-changing austenitic Ni-free stainless steel enriched by Mn and N. It sets a new benchmark in material development and application, synergizing exceptional mechanical attributes with robust ductility. [ABSTRACT FROM AUTHOR]

Superficial weathering in the form of granular disaggregation, powdering and flaking on stone surface is one of the most serious damages to stone heritages, since the surface carries most of the artistic, historical information. The determination of the thickness of the superficially weathered layer of historical stones is critical to their conservation. However, the methodology for quantitative analyses of such thickness remains very limited. In this study, we carefully study the vapor absorption and pore structure evolution of historical sandstones from Guanzhong area with respect to their weathering. We find out that the thickness of superficial weathered layer of Guanzhong sandstones can be derived by following the changes in vapor absorption or pore structure. Such data achieved from various methods developed in this work are consistent with each other and in good agreement with the results obtained by using current techniques such as drilling resistance measurement, the Ruxton method and ultrasonic testing. Among all methods used, pore size distribution analysis requires less sample preparation and measures the thickness of superficial weathered layer of Guanzhong sandstones around 7 mm. [ABSTRACT FROM AUTHOR]

Bamboo biochar was modified by lignin impregnation and microwave irradiation to enhance its performance for CO2 capture. The pore structure of lignin-impregnated biochar was significantly affected by the impregnation ratio. The maximum specific surface area of 377.32 m2 g−1 and micropore volume of 0.163 cm3 g−1 were observed on the biochar with an impregnation ratio of 1:20 (mass ratio of lignin to biochar). Lignin impregnation increased the CO2 adsorption capacity of biochar up to 134.46 mg g−1. Correlation analysis confirmed the crucial role of biochar's pore structure in adsorption. The Avrami model fitted the CO2 capture curves well. The calculation of adsorption activation energy suggested that the adsorption process was dominated by physical mechanism assisted with partial chemical mechanism. Meanwhile, Langmuir isotherm analysis indicated that lignin impregnation transformed the larger pores of biochar into more uniform micropores, thereby making the adsorption process closer to monolayer adsorption. Both the high reusability (89.79–99.06%) after 10 successive cycles and the excellent CO2 selectivity in competitive adsorption confirmed that lignin-impregnated biochar is an outstanding adsorbent for CO2 capture. Highlights: Microwave energy absorbed by biochar carbonized the impregnated lignin to increase micropore structure. CO2 uptake on lignin-impregnated biochar reached 134.46 mg g−1 and was associated with micropore, alkalinity, and temperature. CO2 adsorption on lignin-impregnated biochar was governed by physisorption with slight chemisorption. Lignin-impregnated biochar demonstrated excellent reusability and selectivity in CO2 capture. [ABSTRACT FROM AUTHOR]

The primary objective of this study is to identify and analyze the petrophysical properties of the newly investigated AEB_IIIG member reservoir in Meleiha West Deep (MWD) Field and to classify it into different rock types. Additionally, this research intends to develop mathematical equations that may be utilized to estimate permeability in uncored sections of the same well or in other wells where core samples are unavailable. The analysis focused on the pore hole records of ten wells that were drilled in MWD Field. The reservoir levels were identified, and their petrophysical parameters were evaluated using well logs and core data. We were able to recognize seven different types of rocks (petrophysical static rock type 1 (PSRT1) to PSRT7) using petrography data, the reservoir quality index (RQI), the flow zone index (FZI), R35, hydraulic flow units (HFUs), and stratigraphy modified Lorenz (SML) plots. The analysis of the petrophysical data shows that AEB_IIIG has unsteady net pay thicknesses over the area. It has a range of 8–25% shale volume, 12–17% effective porosity, and 72–92% hydrocarbon saturation. The RQI results show that psrt1, psrt2 and psrt3 have a good reservoir quality as indicated by high R35 and helium porosity, respectively. They contribute with more than 75% of the reservoir production. The equation derived for each rock type of AEB_IIIG reservoir can be employed to forecast the permeability value distribution inside the reservoir. [ABSTRACT FROM AUTHOR]

A literature review has been carried out on the effects of carbon nanotubes (CNT) and macrolevel fiber on concrete porosity indices. The results are presented of investigations into the porosity of nanomodified concrete with dispersed reinforcement (nanofiber reinforced concrete) in terms of the kinetics of water absorption of nanotubes and hard fiber. For dispersed reinforcement, use was made of various hard fibers and their combinations: polymer, basalt, steel wire ones and those from wave-, anchor-, and straight profile sheets. It has been established that the introduction of dispersed fibers results in a change of concrete porosity indices. Hard fibers break up relatively large capillary pores into smaller ones. In this case, the fiber coarseness and its amount in a volume are important. In integrated fiber reinforcement, the size of capillary pores either decreases or does not change at all with respect to the initial concrete. Intense mechanical mix agitation contributes to raising the porosity index. Hard fibers of a more rigid structure tend to demonstrate a higher propeller effect in mixing. The presence of different-scale hard fibers makes it possible to avoid a propeller effect and the need to increase the concrete porosity index. [ABSTRACT FROM AUTHOR]

Polymers have proven to be challenging to cold spray, particularly with high efficiency and quality when using inexpensive nitrogen (N2) and air propellants. Helium (He), when used as a process propellant, can improve spray deposit properties but is often undesirable due to its limited availability and high cost. In this study, additives of multiple particle sizes and materials were mixed with polymer powder in an effort to improve the performance of polymer sprays using mainly N2 as a process propellant. The effects of hard-phase additives on deposit microstructure were investigated by precise ion beam polishing of deposit cross sections and subsequent electron microscope imaging. Additional metrics including the density and post-spray composition of deposits were investigated to quantify the peening effect and the amount of embedded additive. Additives, regardless of size, were observed to embed in the spray deposits. Additionally, hard-phase additives demonstrated nozzle cleaning properties that continually remove polymer fouling on the nozzle walls. Inversely, sprays with polymer powder and no additives tended to clog the nozzle throat and diverging section because of continual fouling. [ABSTRACT FROM AUTHOR]

The present article focuses on the Rayleigh surface wave propagation in homogeneous isotropic thermoelastic medium. This works aims to develop a new nonlocal elasticity model based on three-phase-lag model of hyperbolic thermoelasticity under double porosity structure. New constitutive relations and equations are derived using nonlocal continuum mechanics. State space approach is employed to solve the problem. Frequency equation is derived using appropriate boundary conditions. Path of surface particles is found elliptical at the time of Rayleigh surface wave propagation. Different characteristics of Rayleigh waves are calculated numerically and presented graphically for different wave number. Various characteristics of wave for different thermoelastic models are also presented graphically. The effect of nonlocal parameters and void parameters on phase velocity, attenuation coefficient, penetration depth, and specific loss of Rayleigh waves are shown graphically. Some special cases are deduced from this study which agree with the existing literatures. [ABSTRACT FROM AUTHOR]

In this study, acoustic impedance (P-impedance) distribution in the subsurface of the F3 block, Netherlands is determined using the linear programming (l1-norm) sparse spike inversion (LPSSI) method. The objectives of the study are to characterize the sand channel and extract high-resolution subsurface rock features from the low-resolution seismic data. To estimate rock properties from seismic data, a variety of conventional post-stack seismic inversion techniques are available. However, the LPSSI technique is a reasonably quick and easy-to-compute subsurface model that can be employed for both quantitative and qualitative interpretation. The method is employed in two steps: first, composite traces close to well locations are retrieved and inverted for acoustic P-impedance, and then optimization of the LPSSI parameters is done using comparison with well log impedance. According to the analysis of the composite traces, the algorithm performs well and has a high average correlation (0.98). The F3 block seismic data are utilized in the second stage to estimate the distribution of acoustic impedance in the subsurface by using the LPSSI method. A sand channel-like low impedance anomaly with a range of 3800–7400 m/s g/cc is evident in the inverted acoustic impedance analysis at the 1380–1400 ms time interval. Then, using a deep feed-forward neural network (DFNN), many other crucial rock parameters, including porosity, density, and P-wave velocity, were estimated in the inter-well region to corroborate the sand channel. Following the analysis of these petrophysical properties, a high porosity zone (24–40%), low-density zone (1.9–2.02 g/cc), and low P-wave velocity zone (1700–2300 m/s) are present in the 1380–1400 ms time interval, which aligns with the low impedance zone and validates the presence of the sand channel. [ABSTRACT FROM AUTHOR]

U–Pb geochronology of shocked monazite can be used to date hypervelocity impact events. Impact-induced recrystallisation and formation of mechanical twins in monazite have been shown to result in radiogenic Pb loss and thus constrain impact ages. However, little is known about the effect of porosity on the U–Pb system in shocked monazite. Here we investigate monazite in two impact melt rocks from the Hiawatha impact structure, Greenland by means of nano- and micrometre-scale techniques. Microstructural characterisation by scanning electron and transmission electron microscopy imaging and electron backscatter diffraction reveals shock recrystallisation, microtwins and the development of widespread micrometre- to nanometre-scale porosity. For the first time in shocked monazite, nanophases identified as cubic Pb, Pb3O4, and cerussite (PbCO3) were observed. We also find evidence for interaction with impact melt and fluids, with the formation of micrometre-scale melt-bearing channels, and the precipitation of the Pb-rich nanophases by dissolution–precipitation reactions involving pre-existing Pb-rich high-density clusters. To shed light on the response of monazite to shock metamorphism, high-spatial-resolution U–Pb dating by secondary ion mass spectrometry was completed. Recrystallised grains show the most advanced Pb loss, and together with porous grains yield concordia intercept ages within uncertainty of the previously established zircon U–Pb impact age attributed to the Hiawatha impact structure. Although porous grains alone yielded a less precise age, they are demonstrably useful in constraining impact ages. Observed relatively old apparent ages can be explained by significant retention of radiogenic lead in the form of widespread Pb nanophases. Lastly, we demonstrate that porous monazite is a valuable microtexture to search for when attempting to date poorly constrained impact structures, especially when shocked zircon or recrystallised monazite grains are not present. [ABSTRACT FROM AUTHOR]

A cellular automata model has been developed to study the sintering behavior of ceramic particles. In this model, the only physical rule that drives the evolution of the system is to reduce the energy at the interface between the mass cells and the void cells. The meaning of several computational parameters, such as particle size or computational temperature, were investigated. Experiments of partial sintering of spherical particles of silica were performed and it was verified that this model successfully mimics the neck formation. Moreover, other experimental evidences of the stages of the densification, such as the formation of the intermediate vermicular microstructure or the dependence of porosity with temperature, were also qualitatively simulated. [ABSTRACT FROM AUTHOR]

Porosity has an important influence on the elastic properties of tight sandstone. Using acoustic models to study the matrix mineral modulus of tight sandstone reservoirs can provide an important reference for tight sandstone reservoir evaluation. In this paper, taking tight sandstone as an example, starting from the microscopic pore scale and considering the heterogeneity of the rock skeleton, the effect of the effective stress coefficient of porosity (n) on the elastic properties of tight sandstone was discussed. In addition, the acoustic model was used to construct the calculation method of the matrix mineral shear modulus. The research results showed that the porosity disturbance model can better describe the change law of the elastic properties of the tight sandstone. As the value of n decreases from 1 to 0, the bulk modulus (Kφ) of the unencapsulated rock gradually decreases. In the process of increasing from n=0 to n=4, the rock Kud has a slight increase trend. The fluid pressure does not produce a reverse stress effect on the movement of the rock pore boundary, that is, the fluid pressure does not have any effect on the change of the rock porosity. When n>0, the pore fluid pressure will affect the movement of the rock pore boundary to a certain extent. When the porosity disturbance is not considered, the Kφ value of the formation rock will be overestimated. The Ko of tight sandstone can be obtained using Gassmann fluid substitution equation. The calculation results of modulus parameters accord with the internal mineral composition and structural characteristics of tight sandstone, which shows the effectiveness of the method. [ABSTRACT FROM AUTHOR]

Tight oil has become one of the important energy sources for increasing reserves and production in China's oil and gas field. Chang 8 Member of Ordos Basin shows great exploration potential, and the classification and evaluation of tight reservoirs are critical to reservoir optimization and reserve evaluation. However, the classification and evaluation of tight reservoirs in Chang 8 Member of Ordos Basin have not been unified. Therefore, on the basis of previous research results, this paper systematically studied the petrological characteristics, physical properties and microscopic pore throat structure characteristics of tight sandstone reservoirs by means of rock slice observation, overburden porosity and permeability test and high-pressure mercury injection test. On this basis, the weight coefficient of the correlation between the key parameters and the oil-bearing property of the reservoir is determined by screening the key parameters, and the mathematical model of reservoir classification evaluation is established by using the analytic hierarchy process. The research results show that the reservoir composition maturity of Chang 8 Member in Ordos basin is medium, and the lithology is mainly lithic arkose and feldspathic lithic sandstone. The physical property of Chang 8 reservoir is poor, and it belongs to low porosity, low permeability ultra-low permeability reservoir as a whole. The reservoir space is dominated by intergranular pores and dissolution pores, and micro fractures are developed locally. The pore throat structure of the reservoir is fine, and the pore type is smaller than 10 μm, and the throat and micro throat are dominant with 0.2 μm. Considering porosity, permeability, displacement pressure, average pore throat radius and other parameters comprehensively, normalize each parameter, and determine the weight of each parameter according to its correlation with oil saturation. The reservoir classification and evaluation model were established by using the analytic hierarchy process (AHP), and the reservoir quality index (RMI) is used to classify the reservoirs of Chang 8 Member in Ordos Basin into 4 types. This study can provide a basis for efficient exploration and development of tight oil. [ABSTRACT FROM AUTHOR]

The diffusion behavior of ReO4− (as a surrogate for 99TcO4−) and HSeO3− (as a surrogate for 79HSeO3−) in compacted Wyoming bentonite was investigated. A through-diffusion experiment was conducted to measure the effective diffusion coefficient and the accessible porosity at high salinity. Two multi-porosity models (MP1 and MP2) were employed to analyze the effect of compaction on the accessible porosity, the diffuse double-layer porosity, and the interlayer porosity. The diffuse double-layer porosity increased with increasing the external surface area. [ABSTRACT FROM AUTHOR]

Predictive subsurface transport of selenium oxyanions is important for the assessment of long-term nuclear waste repository performance, as well as monitoring compliance of selenium presence in groundwater once discharged from industry, agriculture or natural seleniferous minerals. The aim of the present study is to quantify the diffusion of selenite and selenate through water-saturated compacted clays of smectite and illite rich geochemistry. Diffusion coefficient (De) values for selenium oxyanions in argillaceous clay are ̴ 10–12 m2s−1 and are nearly an order of magnitude higher in the bentonite clay. Results indicate the role of clay geochemistry in controlling migration of selenium oxyanions through natural clay. [ABSTRACT FROM AUTHOR]