Phase Diffusion Research Articles

Recycling multisource industrial waste residues as green binder for cemented ultrafine tailings backfill: Hydration kinetics, mechanical properties, and solidification mechanism

Incorporating mine tailings with industrial waste residues (IWRs) is progressively used to manufacture filling materials, which provides an eco-friendly disposal method for IWRs and alleviate their impact on the environment. In this study, steel slag (5, 10, 15, 20 wt%), fly ash (5, 10 wt%) and blast furnace slag (52, 57, 65, 74 wt%) as the precursor, carbide slag (16, 18, 20 wt%) and desulfurization gypsum (0, 2, 3 wt%) as the activator were reutilized to synthesize the IWRs-based binder for cemented ultrafine tailings backfill (CUFTB). Experimental tests were conducted to determine the setting time, hydration heat release, mechanical behavior, and microstructure characteristics. The hydration kinetics and solidification mechanism were expounded correspondingly. Results elucidate that the initial and final setting time of CUFTB are respectively 12.08–13.92 h and 16.92–20 h <24 h much longer than the transport time in pipeline and meets the operational requirements of mine site. Hydration process of CUFTB includes initial dissolution, induction, acceleration, deceleration, and decline stages. As the hydration proceeds, the initial stage of CUFTB is regulated by nucleation and crystal growth (NG), and gradually shifted to interactions at phase boundaries (I) or diffusion (D). The high content of carbide slag (20 wt%) promotes the hydration reaction, resulting in the increase of heat release. IWRs-based binder hydrates to form calcite, ettringite, hydroaluminite, and gehlenite. Especially, the gel products are mainly C-A-S-H, C-(Al,Na)-S-H, C-(Al,K)-S-H with Ca/Si ratio <1, demonstrating a fundamental distinction from Portland cement. Under the bonding and padding of hydration products, tailings particles are solidified well. After curing of 28 days, CUFTB exhibit high UCS values exceeding 2.0 MPa, presenting an evident improvement of 26.70% ∼ 39.20% compared to those made of Portland cement. These findings are referential for preparation of cemented paste backfill by reutilizing IWRs in mine filling field.

Medical image encryption system based on a simultaneous permutation and diffusion framework utilizing a new chaotic map

In telemedicine, diverse medical images transmitted between doctors and patients contain sensitive personal information. Thus, there is an urgent need for reliable and efficient medical image encryption to protect these medical images during transmission. In this paper, a simultaneous permutation and diffusion framework (SPDF) is introduced for medical image encryption based on a new chaotic map. Firstly, combining the Chebyshev map and the iterative chaotic map with infinite collapse (ICMIC), we propose a one-dimensional chaotic system (1D-CICMIC) which exhibits higher ergodicity and unpredictability compared to other 1D chaotic maps through comprehensive analyses. Secondly, in order to enhance permutation effect, we modify traditional Josephus traversing with a dynamic scrambling method where the scrambling scheme of the current pixel depends on the value of the previous diffused pixel. Thirdly, we develop a simultaneous permutation and diffusion framework, wherein the diffusion is embedded into the modified Josephus traversing to prevent attackers from targeting the scrambling and diffusion phases separately. Finally, based on 1D-CICMIC and SPDF, an encryption system is proposed. It adopts plaintext correlation in the diffusion operation, which strikes a balance between ciphertext sensitivity and plaintext sensitivity, offering resistance against chosen-plaintext attack (CPA), noise attack and data loss. Simulation results show that the proposed algorithm has high encryption efficiency and can withstand various common attacks.

A robust medical image cryptosystem based on hyperbolic chaotic system and circular bit-shifting-flipping techniques

Due to the hasty growth of digital technology, securing medical images for transmission and storage is a significant issue. Information on the texture of medical images is essential for diagnosis. Hence, protecting these content has become a great challenge in the e-Healthcare system. So, we propose a novel dynamic circular bit shifting and bit-flipping process in the diffusion phase of the image cryptosystem to provide high level protection for the medical image. In the developed framework, at first, the hyperbolic chaotic map is executed for generating three hyper chaotic series and these chaotic series are utilized for encryption process. In encryption process, primarily the secret image is confused by utilizing any two chaotic series, then the confused image is divided into blocks and each block is diffused by executing the proposed dynamic circular bit shifting and bit-flipping process which greatly increases the probability and complexity level of the developed cryptosystem. Evaluation using different medical images represents that the proposed model has robustness, high efficiency, key sensitivity and also has the ability to withstand different attacks. This has been represented using the results of security measures and statistical analysis, such as Shannon entropy (7.997), CC (< 0), NPCR (99.63 %), UACI (37.14 %), SSIM (< 0), FSIM (< 0.5), PSNR (6.88). These results prove that the developed medical crypt can efficiently provide better security for medical images utilized in real time medical application like e-Healthcare and telemedicine.

Phase field-volumetric lattice Boltzmann model of ion uptake in porous nuclear waste form materials under continuous flow

The flow field within the mesopores of sorbent particles plays a crucial role in radionuclide diffusion and ion uptake kinetics, thus, impacting the overall performance of porous nuclear waste form materials. To fundamentally understand the influence of microstructures and material properties on the radionuclide absorption and retention processes requires a coupled multi-physics model that considers the advection and diffusion within the flow field, the reaction at liquid-solid interfaces, and finally, the solid-state diffusion within a complex nanoporous medium. This study employs the volumetric lattice Boltzmann method (VLBM) to accurately and efficiently calculate the steady state velocity field inside the mesopores of sorbent particles. The obtained velocity field is then utilized to calculate the advection of ions in the steady flow. A phase field (PF) model of ion uptake is used to describe the reaction occurring at the solid-liquid interface and diffusion inside the porous medium. The integrated PF-VLBM model is verified in terms of the mass conservation and numerical efficiency and validated qualitatively with experimental observation data. Then, it is applied to study the influence of thermodynamic and kinetic properties, as well as flow field conditions on the ion uptake kinetics. The numerical results demonstrate that the ion uptake kinetics in porous particles has three distinct stages, which is in agreement with the observations in continuous flow experiments. In the first stage, the kinetics is predominantly controlled by the flow field and ion diffusivity in the liquid phase. The kinetics in the second stage is primarily governed by ion diffusivity in the solid phase. In the third stage the system reaches a dynamic equilibrium with a net zero uptake flux at the interface. It is also found that porous structures significantly affect the efficiency and capacity of ion uptake. The simulation results can help to understand the physics behind the observed ion uptake kinetics in experiments and to facilitate the development of constitutive equations that can account for heterogeneous microstructures in engineering performance codes.

Mapping carbon nanotube aspect ratio, concentration and spinning in FCCVD synthesis controlled by sulphur

Floating catalyst chemical vapor deposition (FCCVD) enables ultrafast synthesis of CNTs and other 1D nanoparticles and their direct assembly as macroscopic solids. The chalcogen growth promotor in FCCVD produces high aspect ratio CNTs that can aggregate in the gas phase and form an aerogel which can be continuously spun as macroscopic fibres or sheets. We study the role of sulphur in controlling CNT morphology and aggregation by synthesising CNTs under a wide range of S/C ratios (0.001 to 5 wt.%) and determining their diameter and length distributions, number concentration and form of aggregation. Increasing S/C ratio in this range increases mean number of CNT walls from 1 to 8, decreases mean length from 34 to 6 µm, but CNT number concentration remains approximately constant at 8 × 108#/cm3. Assuming growth within the first 3 cm of the reactor, longitudinal growth rate spans 1.5- 6.5 µm/s for the different CNT morphologies, but with similar mass throughput of 700 attogram/catalyst. This indicates the amount of carbon reaching the catalyst and solidifying as CNT remains constant regardless of the sulphur available in the catalyst, suggesting the rate limiting process is not at the catalyst/promoter interface but instead in the transport of carbonaceous active precursors to the catalyst, either due to their diffusion in the gas phase or decomposition kinetics. The CNTs produced range from polymer-like, which readily bundle and form aerogels, to rod-like that do not. We include aerogelation “phase diagrams” for different CNT concentrations, aspect ratios and CNT bending stiffness.

On the Lanthanide Effect on Functional Properties of 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 Ceramic.

The beneficial effects of lanthanide incorporation into 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (BNT-BT) matrix on its functional properties were investigated. The conventional solid-state method was used for synthesizing samples. The structural refinement revealed that all samples crystallized in R3c rhombohedral symmetry. Raman spectroscopy study was carried out using green laser excitation and revealed that no clear perceptible variation in frequency is observed. Dielectric measurements unveiled that the introduction of rare earth obstructed the depolarization temperature promoted in BNT-BT, the diffusive phase transition decreasing with increasing lanthanide size. Only dysprosium addition showed comparable diffusion constant and dielectric behavior as the unmodified composition. Further, the comparison of the obtained ferroelectric hysteresis and strain-electric field loops revealed that only Dy-phase exhibited interesting properties comparing parent composition. In addition, the incorporation of lanthanides Ln3+ into the BNT-BT matrix led to the development of luminescence characteristics in the visible and near infrared regions, depending on the excitation wavelengths. The simultaneous occurrence of photoluminescence and ferroelectric/piezoelectric properties opens up possibilities for BNT-BT-Ln to exhibit multifunctionality in a wide range of applications.

Theoretical analysis of the effect of isotropy on the effective diffusion coefficient in the porous and agglomerated phase of the electrodes of a PEMFC

In polymer membrane fuel cells (PEMFC), the pore microstructure and the effective diffusion coefficient (Deff\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{eff}$$\\end{document}) of the catalytic layer have a significant impact on the overall performance of the fuel cell. In this work, numerical methods to simulate PEMFC catalytic layers were used to study the effect of isotropy (Ixy\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$I_{xy}$$\\end{document}) on the Deff\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{eff}$$\\end{document}. The proposed methodology studies reconstructed systems by Simulated Annealing imaging with different surface fractions of microstructures composed by two diffusive phases: agglomerates and pores. The Deff\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{eff}$$\\end{document} is determined numerically by the Finite Volume Method solved for Fick's First Law of Diffusion. The results show that the proposed methodology can effectively quantify the effect of isotropy on the Deff\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{eff}$$\\end{document} for both diffusion phases. Two trends were obtained in the magnitude of the Deff\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{eff}$$\\end{document} concerning the change in isotropy: (1) an analytical equation is proposed in this article for Deff≥5%D0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{eff} \\ge 5\\% D_{0}$$\\end{document} and (2) numerical solutions are determined for Deff<5%D0.\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{eff} < 5\\% D_{0} .$$\\end{document} In our analytical equation are both a lineal and a logarithmic sweep. When the surface fraction is ∅=\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\emptyset =$$\\end{document} 50%, the Deff\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{eff}$$\\end{document} decreases more linearly than ∅=10%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\emptyset = 10\\%$$\\end{document} at the beginning of the isotropy change, which indicates that small changes in isotropy in the particulate material modify it drastically; under these conditions the diffusion coefficient in the pore is predominant. (3) When the surface fraction is less than 50%, the Deff\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{eff}$$\\end{document} decreases more exponentially at the beginning and more linearly at the end of the isotropy change, which shows that small isotropy changes in the bar-aligned material drastically alter it. In this trend, diffusion in the agglomerate is less affected by isotropy. The proposed methodology can be used as a design tool to improve the mass transport in porous PEMFC electrodes.

Determination of phase boundaries and diffusion coefficients of copper in spinel CuCr2Se4 and delafossite CuCrSe2 by galvanostatic intermittent titration technique (GITT)

Determination of phase boundaries and diffusion coefficients of copper in spinel CuCr2Se4 and delafossite CuCrSe2 by galvanostatic intermittent titration technique (GITT)

Multi‐chaotic maps and blockchain based image encryption

SummaryThe vast technological developments make data transmission more frequent over networks. So, the data needs to be secured and for that reason, there is a requirement to develop an effective encryption model. This article proposes a novel image encryption model using multi‐chaotic maps and blockchain (MCBE). Chaotic maps have been used in encryption models as chaotic maps have the properties of randomness, and non‐periodicity that get utilized in improving the efficiency of an encryption model. Logistic and tent maps have been employed as multi‐chaotic maps to make the encryption process effective in this work. A logistic map has a simple structure and is easily implementable but has some drawbacks like small keyspace. Keyspace and randomness are enhanced by using a tent map along with a logistic map. The proposed MCBE methodology applies to grayscale or colored images having different file formats and sizes. Initially, in the confusion phase, the permutation of the original image is performed based on a random permutation that changes the original image pixel's position. The encryption model applies multi‐chaotic maps, row‐wise and column‐wise in the diffusion phase to promote the efficiency of the encryption model. Finally, blockchain has been implemented using the SHA‐256 hash function to obtain the encrypted image that enhances the security by increasing the keyspace, to resist brute force attacks. The evaluation performance of the MCBE has been analyzed against various attacks namely statistical attacks, differential attacks, NIST randomness test, noise, and cropping attacks. The evaluated keyspace is which has high key sensitivity with a correlation of encrypted images close to 0. Maximum achieved entropy value of 7.9998, SSIM value between original and encrypted images nearby 0 confirms the dissimilarity. The Number of Pixels Change Rate (NPCR) value of 99.62%, and the value of Unified Average Changed Intensity (UACI) value of 33.54% are within the specified standard range. The calculated correlation coefficient, NPCR, and UACI values have been compared with the existing algorithms, and the results show that the proposed MCBE methodology has better performance than the other state‐of‐the‐art methods. The experimental results indicate that the chaotic ranges generated by multi‐chaotic maps and the SHA‐256 hash function improve the keyspace and security of the encryption model confirming the efficacy of the proposed model MCBE.

Continuous visbreaking of heavy oil in medium and high-pressure steam environments

Continuous visbreaking of heavy oil in a tubular reactor was studied under pressurized steam environments at 10 MPa (MPS) and 18 MPa (HPS). Within the operating range considered, heavy oil and pressurized steam exhibit a liquid-vapor two-phase structure. During the transition from the MPS environment to the HPS environment, the dissolution of water into the oil phase is promoted, thereby reducing the viscosity of the oil phase. According to the lumped reaction kinetics analysis, the reaction behavior of the lumped component VR2 with a boiling point higher than 700 °C determines the visbreaking efficiency in the early visbreaking stage to a large extent. Dealkylation of VR2 and condensation of the lightest lumped component show sensitive responses to improved diffusion in the oil phase. At 400 °C and a space time of 37 min, visbreaking in HPS environment can achieve a viscosity reduction rate of 90%. Meanwhile, the asphaltene content of the product is lower than the feedstock value.

Effects of multi-walled carbon nanotubes on microstructure transformation of water before carbon dioxide hydrate formation

There is no consensus on the micro mechanism of gas hydrate formation. The essence of water conversion into hydrates is the transformation of disorderly arranged water into the water with specific structure under a certain condition. This study used different multi-walled carbon nanotubes (MWCNTs) as solid promoters for gas hydrate formation. By comparing the effects of nanotubes modified with hydroxyl, carboxyl and amidogen on the microstructure transformation of water before CO2 hydrate formation, the micro mechanism and influence rules of gas hydrate formation were systematically study. The results indicated that the conversion of water to hydrates mainly manifested as the mutual conversion of strong/weak hydrogen bonding water. Due to the Brownian motion and dispersion of MWCNTs, the hydrogen bonds of the weak hydrogen-bonded water weakened (the corresponding peak blue shifts), and the distance between water molecules (dO−O) expanded, forming relatively loose hydrate, which was conducive to gas diffusion in the solid hydrate phase and increased the final gas consumption. Meanwhile, the strengthening of strong hydrogen bonded water increased the rate of hydrate formation.

A robust hybrid receiver for binary phase-shift keying discrimination in the presence of phase noise

We address the problem of coherent state discrimination in the presence of phase diffusion. We investigate the role of the HYbrid Near-Optimum Receiver (HYNORE) we proposed in [J. Opt. Soc. Am. B 40 (2023) 705] in the task of mitigating the noise impact. We prove the HYNORE to be a robust receiver, outperforming the Displacement Photon-Number-Resolving (DPNR) receiver and beating the standard quantum limit in particular regimes. We introduce the maximum tolerable phase noise [Formula: see text] as a figure of merit for the receiver robustness and show that HYNORE increases its value with respect to the DPNR receiver.

Improve mechanical properties and corrosion resistance of Al/Sn heterogeneous joints by ultrasonic-assisted liquid phase diffusion bonding

How to obtain a high-strength and corrosion resistance of Al/Sn/Al joint has been a longstanding goal for electronics industry. In this work, 6063Al was joined in the air by ultrasonic-assisted liquid phase diffusion bonding using a Sn filler metal. It was performed by applying an uninterrupted ultrasonic vibration at a heating temperature of 360 ℃, final obtaining a 6063Al joint without enriched-Sn. Under the action of ultrasonic vibrating, the breaking of oxide film, the diffusing of Sn, and dissolving of Al alloy occurred in sequence. It resulted in a transition of bonding interface from Sn/Al to an α-Al/α-Al bonding interface embedded a few Mg2Sn partials, after depleting Sn by grain boundary diffusion. The joints possessed a high strength coefficient of 86.7% of 6063Al base metal and 161.8% of soldering joint. The joint had a better corrosion resistance that the tensile strength only reduced 35.3% after a corroding of 72 h in 3.5 wt% NaCl solution in comparison with the soldering joints. Finally, the evolution of the interface structure and mechanism of improving corrosion resistance were discussed in detail. It is a promising technology for manufacturing high-reliable Al/Sn heterogeneous joints.

Stochastic resetting with refractory periods: pathway formulation and exact results

We look into the problem of stochastic resetting with refractory periods. The model dynamics comprises diffusive and motionless phases. The diffusive phase ends at random time instants, at which the system is reset to a given position—where the system remains at rest for a random time interval, termed the refractory period. A pathway formulation is introduced to derive exact analytical results for the relevant observables in a broad framework, with the resetting time and the refractory period following arbitrary distributions. For the paradigmatic case of Poissonian distributions of the resetting and refractory times, in general with different characteristic rates, closed-form expressions are obtained that successfully describe the relaxation to the steady state. Finally, we focus on the single-target search problem, in which the survival probability and the mean first passage time to the target can be exactly computed. Therein, we also discuss optimal strategies, which show a non-trivial dependence on the refractory period.

Elucidating the role of water films on solute diffusion in unsaturated porous media by improved pore‐scale modeling

AbstractSolute diffusion in partially saturated porous media is an important fundamental process in many natural and environmental systems. At low water saturation, the solute transport is governed by the diffusion in thin water films on the surfaces of solids. In this study, we established an improved pore‐scale simulation framework successfully describing the solute diffusion in variably saturated porous media (e.g., soils), which considers the contribution of the diffusion within the thin water film on the surface of the solid matrix. The model takes into account the liquid–gas distribution in the underlying porous media by the Shan‐Chen lattice Boltzmann Method (LBM) and simulates the solute diffusion in the bulk liquid phase and the water film. Based on the numerical results, an easy‐to‐use theoretical formula was also developed to predict the effective diffusivity in microporous materials at low saturation levels. The average relative error of its prediction with respect to the experimental data from the literature is about 30%, while that of the classical power law exceeds 70%. A simple phase diagram was defined, which allows us to identify the situations under which it is necessary to take the influence of surface water films on the effective diffusivity in unsaturated microporous media into account. The present study improves the pore‐scale model to address solute diffusion in the water films at low water saturation and elucidates the contribution of thin water films on solute transport.

Diffusion of Mobile Technologies in the Area of Financial and Insurance Activities in Poland

The diffusion of innovation in the area of banking and certain financial services is a topic eagerly taken up in empirical research, but in the case of Poland the study of this phenomenon in the area of finance and banking that utilizes the econometric models in question is practically non-existent. This article attempts to fill this research gap to some extent. The main objective of the article is to present a comparative analysis of the rate of mobile technologies diffusion among 3 groups of enterprises in the financial and insurance sectors: banking and lending, insurance and reinsurance, and brokerage and other activities. The occurrence of diffusion of mobile technologies and its rate was studied with the help of a logistic function. Results show that in companies operating in the insurance industry, the phase of rapid growth of mobile innovation diffusion lasted longer than in other groups of enterprises, but the highest dynamics of mobile innovation diffusion in the first phase of this phenomenon was achieved by companies conducting brokerage and other activities.

On simulating diffusional phase transformation in diffusion triple

Diffusion triple technique (stand-alone or composed diffusion multiples) is crucial for high-throughput construction of phase diagrams or extracting diffusion coefficients, taking advantage of the broad two-dimensional (2D) composition variations. However, currently there is a lack of methods available for simulating 2D diffusion accompanied by phase transformations inside diffusion triples. In the present work, we take a noticeable step forward by simulating diffusional phase transformation between the contacting interfaces, especially in the tri-junction of diffusion triple. The present method is an extension of the homogenization model (H. Larsson and L. Höglund, Calphad, 33 (2009) 495–501) to 2D simulations, allowing for disclosure of microstructure evolutions in diffusion triples. The practicability of the present method is demonstrated by comparing the simulation results with the experiment of a Fe-Cr-Ni diffusion triple (as a part of a multiple) from the literature.

Advective and diffusive gas phase transport in vadose zones: Importance for defining vapour risks and natural source zone depletion of petroleum hydrocarbons

Quantifying the interlinked behaviour of the soil microbiome, fluid flow, multi-component transport and partitioning, and biodegradation is key to characterising vapour risks and natural source zone depletion (NSZD) of light non-aqueous phase liquid (LNAPL) petroleum hydrocarbons. Critical to vapour transport and NSZD is transport of gases through the vadose zone (oxygen from the atmosphere, volatile organic compounds (VOCs), methane and carbon dioxide from the zone of LNAPL biodegradation). Volatilisation of VOCs from LNAPL, aerobic biodegradation, methanogenesis and heat production all generate gas pressure changes that may lead to enhanced gas fluxes apart from diffusion. Despite the importance of the gaseous phase dynamics in the vadose zone processes, the relative pressure changes and consequent scales of advective (buoyancy and pressure driven) / diffusive transport is less studied. We use a validated multi-phase multi-component non-isothermal modelling framework to differentiate gas transport mechanisms. We simulate a multicomponent unweathered gasoline LNAPL with high VOC content to maximise the potential for pressure changes due to volatilisation and to enable the joint effects of methanogenesis and shallower aerobic biodegradation of vapours to be assessed, along with heat production. Considering a uniform fine sand profile with LNAPL resident in the water table capillary zone, results suggest that biodegradation plays the key role in gas phase formation and consequent pressure build-up. Results suggest that advection is the main transport mechanism over a thin zone inside the LNAPL/capillary region, where the effective gaseous diffusion is very low. In the bulk of the vadose zone above the LNAPL region, the pressure change is minimal, and gaseous diffusion is dominant. Even for high biodegradation rate cases, pressure build-up due to heat generation (inducing buoyancy effects) is smaller than the contribution of gas formation due to biodegradation. The findings are critical to support broader assumptions of diffusive transport being dominant in vapour transport and NSZD assessments.

Chaos and localized phases in a two-body linear kicked rotor system.

Despite the periodic kicks, a linear kicked rotor (LKR) is an integrable and exactly solvable model in which the kinetic energy term is linear in momentum. It was recently shown that spatially interacting LKRs are also integrable, and results in dynamical localization in the corresponding quantum regime. Similar localized phases exist in other nonintegrable models such as the coupled relativistic kicked rotors. This work, using a two-body LKR, demonstrates two main results; first, it is shown that chaos can be induced in the integrable linear kicked rotor through interactions between the momenta of rotors. An analytical estimate of its Lyapunov exponent is obtained. Second, the quantum dynamics of this chaotic model, upon variation of kicking and interaction strengths, is shown to exhibit a variety of phases: classically induced localization, dynamical localization, subdiffusive, and diffusive phases. We point out the signatures of these phases from the perspective of entanglement production in this system. By defining an effective Hilbert space dimension, the entanglement growth rate can be understood using appropriate random matrix averages.

Manufacturing high-strength and corrosion-resistant 6063Al joints by an ultrasonic-assisted liquid and solid phase diffusion technology

High corrosion-resistance aluminum alloy joint obtained by filler metal containing Sn at relatively low temperatures is a longstanding goal for electronic products. In this research, 6063Al alloys was joined by a novel ultrasonic-assisted diffusion bonding via liquid phase and solid phase synergistic diffusion. It was performed via a hypereutectic interlayer of Zn-30Sn at 360 ℃ to joining 6063Al, obtaining a Zn-Al eutectoid structures joint. By the ultrasonic vibrating, the breaking of oxide film, the diffusing of liquid and solid state had been occurring in sequence during the joining process. It resulted in a series of diffusing phase transitions from “η-Zn phases + Sn-Zn eutectic structures” to “Zn-Al eutectoid structures + η-Zn phases”, and finally to “full Zn-Al eutectoid structures”, which were driven by the grain boundary penetration and chemical potential, respectively. The joints possessed a higher strength than the base metal. The joints with Zn-Al eutectoids have a better corrosion resistance that the tensile strength reduced 37.3% after a corroding of 72 h in 3.5 wt% NaCl solution in comparison with the soldered joints. Finally, the mechanism of ultrasonic accelerated diffusion, joint formation process and mechanism of improving corrosion resistance were discussed in detail.