Training image analysis for three-dimensional reconstruction of porous media

In order to obtain a better sandstone three-dimensional （3D） reconstruction result which is more similar to the original sample, an algorithm based on stationarity for a two-dimensional （2D） training image is proposed. The second-order statistics based on texture features are analyzed to evaluate the scale stationarity of the training image. The multiple-point statistics of the training image are applied to obtain the multiple-point statistics stationarity estimation by the multi-point density function. The results show that the reconstructed 3D structures are closer to reality when the training image has better scale stationarity and multiple-point statistics stationarity by the indications of local percolation probability and two-point probability. Moreover, training images with higher multiple-point statistics stationarity and lower scale stationarity are likely to obtain closer results to the real 3D structure, and vice versa. Thus, stationarity analysis of the training image has far-reaching significance in choosing a better 2D thin section image for the 3D reconstruction of porous media. Especially, high-order statistics perform better than low-order statistics.

Three-dimensional consolidation deformation analysis of porous layered soft soils considering asymmetric effects

Long-term settlements for underground structures, such as tunnels and pipelines, are generally observed after the completion of construction in soft clay. The soil consolidation characteristic has great influences on the long-term deformation for underground structures. A three-dimensional consolidation analysis method under the asymmetric loads is developed for porous layered soil based on Biot's classical theory. Time-displacement effects can be fully considered in this work and the analytical solutions are obtained by the state space approach in the Cartesian coordinate. The Laplace and double Fourier integral transform are applied to the state variables in order to reduce the partial differential equations into algebraic differential equations and easily obtain the state space solution. Starting from the governing equations of saturated porous soil, the basic relationship of state space variables is established between the ground surface and the arbitrary depth in the integral transform domain. Based on the continuity conditions and boundary conditions of the multi-layered pore soil model, the multi-layered pore half-space solutions are obtained by means of the transfer matrix method and the inverse integral transforms. The accuracy of proposed method is demonstrated with existing classical solutions. The results indicate that the porous homogenous soils as well as the porous non-homogenous layered soils can be considered in this proposed method. When the consolidation time factor is 0.01, the value of immediate consolidation settlement coefficient calculated by the weighted homogenous solution is 27.4% bigger than the one calculated by the non-homogeneity solution. When the consolidation time factor is 0.05, the value of excess pore water pressure for the weighted homogenous solution is 27.2% bigger than the one for the non-homogeneity solution. It is shown that the material non-homogeneity has a great influence on the long-term settlements and the dissipation process of excess pore water pressure.

In-situ formation of cobalt phosphide nanoparticles confined in three-dimensional porous carbon for high-performing zinc-air battery and water splitting

The rational design of efficient and stable carbon-based electrocatalysts for oxygen reduction and oxygen evolution reactions is crucial for improving energy density and long-term stability of rechargeable zinc-air batteries(ZABs).Herein,a general and controllable synthesis method was developed to prepare three-dimensional(3D)porous carbon composites embedded with diverse metal phosphide nanocrystallites by interfacial coordination of transition metal ions with phytic acid-doped polyaniline networks and subsequent pyrolysis.Phytic acid as the dopant of polyaniline provides favorable anchoring sites for metal ions owing to the coordination interaction.Specifically,adjusting the concentration of adsorbed cobalt ions can achieve the phase regulation of transition metal phosphides.Thus,with abundant cobalt phosphide nanoparticles and nitrogen-and phosphorus-doping sites,the obtained carbon-based electrocatalysts exhibited efficient electrocatalytic activities toward oxygen reduction and evolution reactions.Consequently,the fabricated ZABs exhibited a high energy density,high power density of 368 mW cm^(-2),and good cycling/mechanical stability,which could power water splitting for integrated device fabrication with high gas yields.

Three-dimensional porous In_(2)O_(3) arrays for self-powered transparent solar-blind photodetectors with high responsivity and excellent spectral selectivity

Transparent solar-blind ultraviolet photodetectors(SBUV PDs)have extensive applications in versatile scenarios,such as optical communication.However,it is still challenging to simultaneously achieve high responsivity,high transparency,and satisfying self-powered capability.Here,we demonstrated high-performance,transparent,and self-powered photoelectrochemical-type(PEC)SBUV PDs based on vertically grown ultrathin In_(2)O_(3) nanosheet arrays(NAs)with a three-dimensional(3D)porous structure.The 3D porous structure simultaneously improves the transmittance in the visible light region,accelerates interfacial reaction kinetics,and promotes photogenerated carrier transport.The performance of In_(2)O_(3) NAs photoanodes exceeds most reported self-powered PEC SBUV PDs,exhibiting a high transmittance of approximately 80%in the visible light region,a high responsivity of 86.15 mA/W for 254 nm light irradiation,a fast response speed of 15/18 ms,and good multicycle stability.The In_(2)O_(3) NAs also show excellent spectral selectivity with an ultrahigh solar-blind rejection ratio of 1319.30,attributed to the quantum confinement effect induced by the ultrathin feature(2-3 nm).Furthermore,In_(2)O_(3) NAs photoanodes show good capability in underwater optical communication.Our work demonstrated that a 3D porous structure is a powerful strategy to synchronously achieve high responsivity and transparency and provides a new perspective for designing high-performance,transparent,and self-powered PEC SBUV PDs.

Seismic responses of a hemispherical alluvial valley to SV waves: a three-dimensional analytical approximation

Abstract An analytical solution to the three-dimen-sional scattering and diffraction of plane SV-waves by a saturated hemispherical alluvial valley in elastic half-space is obtained by using Fourier-Bessel series expan-sion technique. The hemispherical alluvial valley with saturated soil deposits is simulated with Biot＇s dynamic theory for saturated porous media. The following conclusions based on numerical results can be drawn： （1） there are a significant differences in the seismic response simulation between the previous single-phase models and the present two-phase model; （2） the nor-malized displacements on the free surface of the alluvial valley depend mainly on the incident wave angles, the dimensionless frequency of the incident SV waves and the porosity of sediments; （3） with the increase of the incident angle, the displacement distributions become more complicated; and the displacements on the free surface of the alluvial valley increase as the porosity of sediments increases.

Three-dimensionally Perforated Calcium Phosphate Ceramics

Porous calcium phosphate ceramics were produced by compression molding using a special mold followed by sintering. The porous calcium phosphate ceramics have three-dimensional and penetrated open pores 380-400μm in diacneter spaced at intervals of 200μm. The layers of the linear penetration pores alternately lay perpendicular to pore direction. The porosity was 59%-65% . The Ca/ P molar ratios of the porous calcium phos phate ceramics range from 1.5 to 1.85. A binder cantaining methyl cellulose was most effective for preparing the powder compact among vinyl acetate, polyvinyl alcohol, starch, stearic acid, methyl cellulose and their mixtures . Stainless steel, polystyrene, nylon and bamboo were used as the long columnar dies for the penetrated open pores. When polystyrene, nylon and bamboo were used as the long columnar male dies, the dies were burned oat during the sintering process. Using stainless steel as the male dies with the removal of the dies before heat treatment resulted in a higher level of densification of the calcium phosphate ceramic.

Three-dimensional MXene-encapsulated porous Ni-NDC nanosheets as anodes for enhanced lithium-ion batteries

Although metal–organic frameworks have been heavily tested as the anode materials for lithium-ion batteries(LIBs),the poorer conductivity,easy collapse of frameworks,and serious volume expansion limit their further application in LIBs.Herein,we report a facile approach to obtain MXene-encapsulated porous Ni-naphthalene dicarboxylic acid(Ni-NDC)nanosheets by hybridizing ultrathin Ti_(3)C_(2)MXene and three-dimensional(3D)Ni-NDC nanosheet aggregates.In the structure of Ni-NDC/MXene hybrids,the interlayer hydrogen-bond interaction between Ni-NDC and MXene can effectively increase the interlayer spacing and further inhibit the oxidation of pure MXene.Hence,the introduction of MXene(a conductive matrix)could further improve the conductivity of Ni-NDC,avoid self-agglomeration,and buffer the volume expansion of Ni-NDC nanosheets.Benefiting from the synergistic effects between Ni-NDC and MXene,Ni-NDC/MXene hybrid electrode exhibits a reversible discharge capacity(579.8 mA∙h∙g^(−1)at 100 mA∙g^(−1)after 100 cycles)and good long-term cycling performance(310 mA∙h∙g^(−1)at 1 A∙g^(−1)after 500 cycles).

A Three-Dimensional Silicon-Diacetylene Porous Organic Radical Polymer

Radical-containing porous organic polymers(POPs)have drawn great interest in various applications.However,the synthesis of radical POPs remains challenging due to the unstable nature of organic radicals.Here,a persistent and stable three-dimensional silicon-diacetylene porous organic radical polymer was synthesized via a classic Eglinton homocoupling reaction of tetraethynylsilane.The presence of carbon radicals in this material was confirmed by electron paramagnetic resonance,and its paramagnetic behavior was analyzed by a superconducting quantum interference device.This unique material has a low-lying lowest unoccupied molecular orbital(LUMO)energy level(−5.47 eV)and a small energy gap(ca.1.46 eV),which shows long-term cycling stability and excellent rate capability as an anode material for lithium-ion batteries,demonstrating potential application in energy fields.

Experimental investigation of methane hydrate decomposition by depressurizing in porous media with 3-Dimension device

In order to simulate the behavior of gas hydrate formation and decomposition,a 3-Dimension experimental device was built,consisting of a high-pressure reactor with an inner diameter of 300 mm,effective height of 100 mm,and operation pressure of 16 MPa.Eight thermal resistances were mounted in the porous media at different depthes and radiuses to detect the temperature distribution during the hydrate formation/decomposition.To collect the pressure,temperature,and flux of gas production data,the Monitor and Control Generated System（MCGS） was used.Using this device,the formation and decomposition behavior of methane hydrate in the 20 ～ 40 mesh natural sand with salinity of 3.35 wt% was examined.It was found that the front of formation or decomposition of hydrate can be judged by the temperature distribution.The amount of hydrate formation can also be evaluated by the temperature change.During the hydrate decomposition process,the temperature curves indicated that the hydrate in the top and bottom of reactor dissociated earlier than in the inner.The hydrate decomposition front gradually moved from porous media surface to inner and kept a shape of column form,with different moving speed at different surface position.The proper decomposition pressure was also determined.

Generalization of Wave Motions and Application to Porous Media

The examination of wave motions is traditionally based on the differential equation of D’Alambert, the solution of which describes the motion along a single dimension, while its bidimensional extension takes on the concept of plane waves. Considering these elements and/or limits, the research is divided into two parts: in the first are written the differential equations relating on the conditions two/three-dimensional for which the exact solutions are found;in the second the concepts are extended to the analysis of the propagation of wave motions in porous media both artificial and natural. In the end the work is completed by a series of tests, which show the high reliability of the physical-mathematical models proposed.

Three-dimensional porous superaerophobic nickel nanoflower electrodes for high-performance hydrazine oxidation

Finding inexpensive electrodes with high activity and stability is key to realize the practical application of fuel cells. Here, we report the fabrication of three-dimensional （3D） porous nickel nanoflower （3D-PNNF） electrodes via an in situ reduction method. The 3D-PNNF electrodes have a high surface area, show tight binding to the electroconductive substrate, and most importantly, have superaerophobic （bubble repellent） surfaces. Therefore, the electrocatalytic hydrazine oxidation performance of the 3D-PNNF electrodes was much higher than that of commercial Pt/C catalysts because of its ultra-weak gas-bubble adhesion and ultra-fast gas-bubble release. Furthermore, the 3D-PNNF electrodes showed ultra-high stability even under a high current density （260 mA/cm^2）, which makes it promising for practical applications. In addition, the construction of superaerophobic nanostructures could also be beneficial for other gas evolution processes （e.g., hydrogen evolution reaction）.

Preparation and evaluation of nano-hydroxyapatite/poly(styrene-divinylbenzene) porous microsphere for aspirin carrier

A novel vehicle for the delivery of aspirin （ASA） was prepared from porous nano-hydroxyapafite/poly（styrene-divinylbenzene） [nano-HAP/P（St-DVB）] composite microspheres by grafting nano-HAP [Ca10（PO4）6（OH）2] onto porous P（St-DVB） micro- spheres. Four types of porous composite microspheres were prepared, each with different nano-HAP contents. The ASA-loaded composite microspheres prepared with 10% and 15% nano-HAP （mass ratio） exhibited excellent buoyancy with relatively short instantaneous floating time （within l0 min） and a long sustained floating time （12 h） in simulated gastric juice. They also offered good sustained release of ASA （up to 8 h）. Furthermore, these composite microspheres displayed good buff- ering capacity that prevented the buildup of acidity caused by hydrolysis of ASA, keeping the pH of gastric juice within the normal range （pH 0.9 to 1.5）. The results showed that porous nano-HAP/P（St-DVB） composite microspheres prepared with 10% and 15% nano-HAP could be used as a novel drug carrier for ASA, providing a sustained release dose without leading to stomach irritation, a side effect that is often associated with ASA medication.

Tuning dual three-dimensional porous copper/graphite composite to achieve diversified utilization of copper current collector for lithium storage

Graphite anode materials are widely used in commercial lithium-ion batteries;however, the long electron/ion transportation path restricted its high energy storage. In this experiment, we designed a copper/graphite composite with a dual three-dimensional(3 D) continuous porous structure combining used nonsolvent-induced phase separation and heat treatment, in which a large amount of graphite is embedded in the 3 D porous copper/carbon architecture. In the novel structure, not only the electron and Li^(+) transmission performances are improved, but also the space of current collector is fully utilized. Meanwhile,carbonized polyacrylonitrile network stabilizes the interface between graphite and copper matrix. The obtained copper/graphite composite anode has an initial discharge capacity of 524.6 mAh·g^(-1), a holding capacity of350 mAh·g^(-1) and excellent cycle stability(299.3 mAh·g^(-1) after 180 cycles at 0.1 C rate), exhibiting good electrochemical performance. The experimental results show that the mass loading of the copper/graphite composite electrode material is about 4.39 mg·cm^(-2). We also envisage replacing graphite with other high-capacity active materials to fill the current collector, which can provide a reference for the future development of next-generation advanced electrodes.

MicroED as a powerful technique for the structure determination of complex porous materials

Porous materials have garnered significant attention in recent years.Understanding the intrinsic relationship between their structures and properties requires precise knowledge of their atomic structures.Single-crystal X-ray diffraction(SCXRD)has traditionally been the primary method for elucidating such structures,but it demands large,high-quality crystals,often exceeding 5μm in size.The growth of these crystals can be a time-consuming process,especially for one-and two-dimensional materials.To explore structures at the nanoscale,MicroED(microcrystal electron diffraction(ED))offers unprecedented insights into the realm of nanomaterials.This revolutionary technique enables researchers to uncover intricate details within nanoscale structures,promising to reshape our fundamental understanding of materials.In this review,we delve into the applications of MicroED in the study of various porous materials,including zeolites,metal-organic frameworks(MOFs),and covalent organic frameworks(COFs).We emphasize the pivotal role of MicroED in nanomaterial characterization,enabling precise crystallographic analysis and phase identification.

Honeycomb-like MoCo alloy on 3D nitrogen-doped porous graphene for efficient hydrogen evolution reaction

An efficient electrocatalyst is indispensable to significantly reduce energy consumption and accelerate the conversion efficiency of water splitting.In this work,the honeycomb-like porous MoCo alloy on nitrogen-doped three-dimensional(3D)porous graphene substrate(Mo_(0.3)Co_(0.7)@NPG)has been synthesized from the annealing of layered double hydroxide(MoCo-LDH@NPG).Especially,the Mo_(0.3)Co_(0.7)@NPG exhibits low hydrogen evolution overpotential of 75 mV(10 mA·cm^(-2))and a Tafel slope of 69.9 mV·dec^(-1),which can be attributed to highly conductive NPG substrate,the unique nanostructure and the synergistic effect of Mo and Co.Moreover,the Mo_(0.3)Co_(0.7)@NPG can maintain the original morphology and high catalytic activity after 50-h stability test.This work proposes a general strategy to synthesize a multi-element alloy on conductive substrates with high porosity for electrocatalytic reaction.

Three-dimensional porous electrodes for direct formate fuel cells

The dual-layer electrode for fuel cells is typically prepared by binding discrete catalyst nanoparticles onto a diffusion layer.Such a random packing forms a dense catalyst layer and thus creates a barrier for mass/ion transport,particularly for direct liquid fuel cells.Three-dimensional porous electrodes,a thin nano-porous catalyst layer uniformly distributed on the matrix surface of a foam-like structure,are typically employed to improve the mass/ion transport.Such a three-dimensional porous structure brings two critical advantages:(i)reduced mass/ion transport resistance for the delivery of the reactants via shortening the transport distance and(ii)enlarged electrochemical surface area,via reducing the dead pores,isolated particles and severe aggregations,for interfacial reactions.Moreover,the three-dimensional design is capable of fabricating binder-free electrodes,thereby eliminating the use of ionomers/binders and simplifying the fabrication process.In this work,three types of three-dimensional porous electrode are fabricated,via different preparation methods,for direct formate fuel cells:(i)Pd/C nanoparticles coating on the nickel foam matrix surface(Pd-C/NF)via a dip-coating method,(ii)Pd nanoparticles depositing on the nickel foam matrix surface(Pd/NF)via reduction reaction deposition,and(iii)Pd nanoparticles embedding in the nickel foam matrix(Pd/(in)NF)via replacement reaction deposition.The latter two are binder-free three-dimensional porous electrodes.As a comparison,a conventional dual-layer design,Pd/C nanoparticles painting on the nickel foam layer(Pd-C//NF),is also prepared via direct painting method.It is shown that the use of the three-dimensional Pd-C/NF electrode as the anode in a direct formate fuel cell results in a peak power density of 45.0 mW cm^(-2)at 60℃,which is two times of that achieved by using a conventional dual-layer design(19.5 mW cm^(-2)).This performance improvement is mainly attributed to the unique three-dimensional structure design,which effectively enhances the mass/ion transport through the porous electrode and enlarges the electrochemical surface area(accessible active area)for interfacial reactions.In addition,the delivery of the fuel solution is still sufficient even when the flow rate is as low as 2.0 mL min^(-1).It is also demonstrated that direct formate fuel cells using two binder-free electrodes yield the peak power densities of 13.5 mW cm^(-2)(Pd/(in)NF)and 14.0 mW cm^(-2)(Pd/NF)at 60℃,respectively,both of which are much lower than the power density achieved by using the Pd-C/NF electrode.This is because the electrochemical surface areas of two binderfree electrodes are much smaller than the Pd/C-based electrodes,since the specific area of Pd/C nanoparticles is much larger.

An experimental study on horizontal well waterflooding in the Cretaceous porous carbonate reservoir of Oman

Porous carbonate reservoirs,prevalent in the Middle East,are lithologically dominated by bioclastic limestones,exhibiting high porosity,low permeability,intricate pore structure,and strong heterogeneity.Waterflooding through horizontal wells is commonly used for exploiting these reservoirs.However,challenges persist,such as significant uncertainty and complex operational procedures regarding adjustment effects during the exploitation.The USH reservoir of the Cretaceous D oilfield,Oman exemplifies typical porous carbonate reservoirs.It initially underwent depletion drive using vertical wells,followed by horizontal well waterflooding in the late stage.Currently,the oilfield is confronted with substantial developmental challenges,involving the understanding of residual oil distribution,effective water cut control,and sustaining oil production since it has entered the late development stage.Employing a microscopic visualization displacement system equipped with electrodes,this study elucidated the waterflooding mechanisms and residual oil distribution in the late-stage development of the USH reservoir.The results reveal that the reservoir's vertical stacking patterns act as the main factor affecting the horizontal well waterflooding efficacy.Distinct water flow channels emerge under varying reservoir stacking patterns,with post-waterflooding residual oil predominantly distributed at the reservoir's top and bottom.The oil recovery can be enhanced by adjusting the waterflooding's flow line and intensity.The findings of this study will provide theoretical insights of waterflooding mechanisms and injection-production adjustments for exploiting other porous carbonate reservoirs in the Middle East through horizontal wells.

Darcy–Forchheimer Three-Dimensional Flow of Williamson Nanofluid over a Convectively Heated Nonlinear Stretching Surface

The present study elaborates three-dimensional flow of Williamson nanoliquid over a nonlinear stretchable surface. Fluid flow obeys Darcy–Forchheimer porous medium. A bidirectional nonlinear stretching surface generates the flow. Convective surface condition of heat transfer is taken into consideration. Further the zero nanoparticles mass flux condition is imposed at the boundary. Effects of thermophoresis and Brownian diffusion are considered. Assumption of boundary layer has been employed in the problem formulation. Convergent series solutions for the nonlinear governing system are established through the optimal homotopy analysis method(OHAM). Graphs have been sketched in order to analyze that how the velocity, temperature and concentration distributions are affected by distinct emerging flow parameters. Skin friction coefficients and local Nusselt number are also computed and discussed.

Ball-flower-like carbon microspheres via a three-dimensional replication strategy as a high-capacity cathode in lithium–oxygen batteries

The robust porous architectures of active materials are highly desired for oxygen electrodes in lithium–oxygen batteries to enable high capacities and excellent reversibility. Herein, we report a novel three-dimensional replication strategy to fabricate three-dimensional architecture of porous carbon for oxygen electrodes in lithium–oxygen batteries. As a demonstration, ball-flower-like carbon microspheres assembled with tortuous hollow carbon nanosheets are successfully prepared by completely replicating the morphology of the nanostructured zinc oxide template and utilizing the polydopamine coating layer as the carbon source.When used as the active material for oxygen electrodes, the three-dimensional porous architecture of the prepared ballflower-like carbon microspheres can accommodate the discharge product lithium peroxide and simultaneously maintain the ions and gas diffusion paths. Moreover, their high degrees of defectiveness by nitrogen doping provide sufficient active sites for oxygen reduction/evolution reaction.Thus the prepared ball-flower-like carbon microspheres demonstrate a high capacity of 9,163.7 mA h g-1 and excellent reversibility. This work presents an effective way to prepare three-dimensional architectures of porous carbon by replicating the controllable nanostructures of transition metal oxide templates for energy storage and conversion applications.

THEORY AND APPLICATION OF FRACTIONAL STEP CHARACTERISTIC FINITE DIFFERENCE METHOD IN NUMERICAL SIMULATION OF SECOND ORDER ENHANCED OIL PRODUCTION

A kind of second-order implicit fractional step characteristic finite difference method is presented in this paper for the numerically simulation coupled system of enhanced （chemical） oil production in porous media. Some techniques, such as the calculus of variations, energy analysis method, commutativity of the products of difference operators, decomposition of high-order difference operators and the theory of a priori estimates are introduced and an optimal order error estimates in l^2 norm is derived. This method has been applied successfully to the numerical simulation of enhanced oil production in actual oilfields, and the simulation results ate quite interesting and satisfactory.