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Over the past decade, the global research agenda focused on finding paths to the future development of chemistry. Chemical detection and measurement is an important and fundamental discipline of chemistry and it keeps playing a significant role in chemical research in the next 10–15 years. The goal of chemical detection is to overcome the state-of-art temporospatial resolution limit. Meanwhile, the application of modern chemical technology to serve human health is also highly concerned. We have summarized 10 aspects related to the field, including complex samples analysis, biomacromolecule structure and function, single-entity analysis, large-scale scientific instrument, rapid chemical and electron transfer processes, big data and artificial intelligence, bioimaging, in vivo real-time detection, biomolecule recognition and disease therapy, and public health screening. In this review, we outlined the history and the frontiers of chemical detection and measurements in enhancing the development of chemical sciences. Moreover, we also focused on the major challenges that should be solved in the future in which researchers should develop new techniques and analytical methods to drastically accelerate chemical sciences.

A BDDC preconditioner with adaptive coarse space for advection-diffusion problems discretized by stabilized finite element method is proposed. Since the bilinear form of the corresponding variational form is nonsymmetric and positive definite (NSPD), the adaptive BDDC preconditioner, which is always used for solving the symmetric and positive definite (SPD) problems, is extended to solve the nonsymmetric problems. By decomposing the original bilinear form to the symmetric part and the skew-symmetric part, a series of local generalized eigenvalue problems with respect to the symmetric part of the original bilinear form for the common faces/edges are designed and analyzed to form the adaptive coarse components. Numerical results are presented for model problems with various viscosities to show the performance of the proposed preconditioner.

Landfills are sequentially filled by solid waste lifts, thus normal stress on the liner interface changes in different shear stages, which may affect selection of interface strength in landfill slope stability analysis. Shear tests were conducted at the liner interfaces of geomembrane/geotextile (GM/GT) and geomembrane/geocomposite/sand (GM/GC/Sand), and the normal stress changed in different shear stages. Values of friction angles on both the GM/GT and GM/GC/Sand interfaces obtained by direct and simple shear tests under increasing normal stress in the hardening, softening, and large-displacement stages were lower than those obtained by the traditional direct shear test. The reduction was greater for peak friction angles. Since the peak liner interface strength obtained by staged loading is lower than the peak interface strength by using the traditional shear test method, using the peak shear strength obtained from the traditional direct shear test for the base floor liner to conduct slope stability analysis may cause an un-conservative result. It is necessary to consider the effects of normal stress changes on the liner interface strength in landfill slope stability analysis.

Interactions of rare earth elements with Ti–Si system at high temperatures are of academic interests for the development of refractory lightweight structural materials. As part of the fundamental r...

The algebraic multigrain (AMG) is one of the most frequently used algorithms for the solution of large-scale sparse linear systems in many realistic simulations of science and engineering applications. However, as the concurrency of supercomputers increasing, the AMG solver increasingly leads to poor parallel scalability due to its coarse-level construction in the setup phase. In this paper, to improve the parallel scalability of the traditional AMG to solve the sequence of sparse linear systems arising from PDE-based simulations, we propose a new AMG procedure called αSetup-AMG based on an adaptive setup strategy. The main idea behind αSetup-AMG is the introduction of a setup condition in the coarsening process so that the setup is constructed as it needed instead of constructing in advance via an independent phase in the traditional procedure. As a result, αSetup-AMG requires fewer setup cost and level numbers for the sequence of linear systems. The numerical results on thousands of cores for a radiation hydrodynamics simulation in the inertial confinement fusion (ICF) application show the significant improvement in the efficiency of the αSetup-AMG solver.

The iridium is an important metal which has excellent resistance to corrosion at high temperature. L12 intermetallic compounds i.e. Ir3Nb and Ir3Zr, with similar lattice parameters are ideal for wo...

The pore characteristics of cake formed by cake filtration are quantified. Intra-aggregate pores occupy more than 78% of the total pore content of the cake, but the average pore diameter (~10 μm) o...

Highly efficient enrichment of target glycopeptides plays a crucial role in glycoproteome research. Owing to their large surface area and excellent hydrophilicity, 2-D Hf-BTB nanosheets showed effective and selective enrichment of 78 glycopeptides derived from 29 glycoproteins with 90 N-glycosylation sites from just 2 μL of human serum.

The paper investigates a non-intrusive parallel time integration with multigrid for space-fractional diffusion equations in two spatial dimensions, which is discretized by the space–time finite element method to propagate solutions. We develop a multigrid-reduction-in-time (MGRIT) algorithm with time-dependent time-grid propagators and provide its two-level convergence theory under the assumptions of the stability and simultaneous diagonalizability on time-grid propagators. Numerical results show that the proposed method possesses the saturation error order, theoretical results of the two-level variant deliver good predictions for our model problems, and significant speedups of the MGRIT can be achieved when compared to the two-level variant with F-relaxation (an equivalent version of the parareal algorithm) and the sequential time-stepping approach.

In this paper, we propose a space–time finite element method for the multi-term time–space fractional diffusion equation. First, some fractional derivative spaces are listed, some properties of the fractional derivatives and fractional derivative spaces are given, some definitions and properties of finite element spaces are introduced, and a space–time finite element fully discrete scheme for the considered problem is developed. Second, the existence, uniqueness and stability of the obtained numerical scheme are discussed. Third, under the hypothesis about singular behavior of exact solution near t = 0 , the convergence is investigated in detail based on the suitable graded time mesh. At last, some numerical tests are given to verify the rationality and effectiveness of our method.

A diffuse interface lattice Boltzmann model for thermocapillary flows with large density ratio and thermophysical parameters contrasts is developed in this paper. In this model, three distribution functions are used to describe the evolution of phase field, velocity field and temperature field. The conservative Allen-Cahn-based lattce Boltzmann equation which has good numerical stability in simulating multiphase flows at high density ratio is employed to capture the phase interface. The velocity-based lattice Boltzmann equation is utilized to capture the hydrodynamics with thermocapillary effect. In particular, a lattice Boltzmann scheme is proposed to solve the temperature field equation based on the diffuse interface concept, in which the source term is computed locally. Unlike previous lattice Boltzmann model for thermocapillary flows, the thermophysical parameters (heat capacitance and thermal conductivity) of two fluids are allowed to be different. The present model is validated by simulating several numerical examples. Numerical results indicate the reliability of proposed diffuse interface lattice Boltzmann model in simulating thermocapillary flows with large density ratio (up to 1000) and thermophysical parameters contrasts. Moreover, we also derive an unsteady solution for thermocapillary-driven flow in a heated microchannel with two superimposed planar fluids, which can be used to assess the numerical accuracy of numerical algorithm for thermocapillary flows.

Separation of monophosphopeptides from multi-phosphopeptides in complex biological samples is significant in the study of protein kinase signal transduction pathways. To the best of our knowledge, very few materials have been reported that could selectively enrich monophosphopeptides because of the chemical difficulty in retaining the intermediate monophosphopeptides and excluding both non-phosphopeptides and multi-phosphopeptides in acidic conditions, which requires unique interactions to balance the metallic affinity and the hydrophobicity. With the large surface area, abundant accessible active sites, and ultrathin structures, two-dimensional (2-D) metal-organic framework (MOF) Hf-1,3,5-tris(4-carboxyphenyl)benzene (BTB) nanosheets were rationally selected. Due to the elongated organic ligands and the balance between metallic affinity of clusters and hydrophobicity from ligands, the 2-D Hf-BTB nanosheets exhibited unique enrichment selectivity toward monophosphopeptides. The 2-D MOF nanosheets demonstrated excellent sensitivity (detection limit of 0.4 fmol μL-1) and selectivity [1:1000 molar ratios of β-casein/BSA (bovine serum albumin)] in model phosphopeptides enrichment. The nanosheets were implemented for the analysis of nonfat milk and human saliva samples as well as in situ isotope labeling for dysregulated phosphopeptides from patients' serum with anal canal inflammation, exhibiting 6.6-fold upregulation of serum phosphopeptide HS4 (ADpSGEGDFLAEGGGVR) compared to the control healthy serum. The proteomics analysis of mouse brain cortical samples associated with Alzheimer's disease, which were from Akt (protein kinase B) conditional knockout mouse and littermate control mouse, was further established with 2-D Hf-BTB nanosheets. With high capture efficiency for monophosphopeptides, this method was capable of distinguishing the difference of monophosphopeptides from microtubule-associated protein τ (MAPT/τ) between the Akt knockout sample and control sample.

Metal-organic frameworks (MOFs) have drawn great interest in recent decades due to their fascinating structures, unusual physical properties, versatile modification strategies, and biological compatibilities. In this review, we describe recent progress in the application of MOFs to matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). Owing to their high porosities, specific affinities, and photon absorption capacities, MOFs can be used as solid adsorbents to selectively capture peptides (including endogenous peptides, phosphopeptides, and glycopeptides) and as matrices in MALDI MS. Current developments in and future prospects for this field of research are also discussed.

An immersed boundary-lattice Boltzmann method for electro-thermo-convection in complex geometries is introduced in this paper. The modified governing equations with the additional source terms, including the Navier-stokes equations, the temperature field equation, the electric potential equation and the conservation equation of electric charge, are solved by the lattice Boltzmann method. Both Dirichlet-type and Neumann-type boundary conditions on curved boundaries are treated by the immersed boundary method. The numerical accuracy of the present method is verified by three simple cases with the curved boundary conditions. Moreover, the electro-thermo-convection problems with the prescribed wall temperature and wall heat flux for different geometric configurations are studied. The effects of the thermal Rayleigh number, the electric Rayleigh number, the aspect ratio and the Prandtl number on the streamlines, isotherms, charge density distribution and surface-averaged Nusselt number are investigated. The results indicate that increasing the electric Rayleigh number can enhance the heat transfer rate and change the flow field structure. The coexistence and competition of the buoyancy force and electric force can be also observed.

With the growing demand for underwater refill engineering, the construction technology of implementing fluidized solidification in underwater pouring has recently received increased attention. Howe...

A cold fluid flowing past a hot stationary scalene prolate ellipsoid is numerically studied via a three-dimensional immersed boundary-lattice Boltzmann model (IB-LBM). First, axisymmetric ellipsoids are considered for verification purposes, and good agreement is found between obtained drag coefficient (Cd) and averaged Nusselt number (Nu) and previously reported results. Subsequently, 81 case studies are conducted by changing shape (2 ≤ Ar1, Ar2 ≤ 6) and incident angle (0° ≤ θ ≤ 90°) of the ellipsoid as well as the Reynolds number (25 ≤ Re ≤ 200). In this study, we particularly consider scalene prolate ellipsoids with unequal Ar1 and Ar2, which have not been studied in detail before. Effects of different factors on momentum and heat transfer characteristics between solid and fluid phases are understood based on the analysis of numerical results. Available formulas reported in the literature are also briefly reviewed. Finally, new correlations for both Cd and Nu are developed using the most important factors with average deviations of 3.875% for Cd and 1.598% for Nu, respectively. These proposed correlations can be used to facilitate the phase coupling in the multi-phase flow modelling.

A fully resolved simulation (FRS) method for particulate flows with heat transfer based on the smoothed profile-lattice Boltzmann method (SP-LBM) is developed. The governing equations of the flow field and the temperature field are solved by the LBM. The fluid-particle interaction is treated by the SPM. Both the no-slip boundary condition for the velocity field and the conjugate interface conditions for the temperature field are satisfied. Unlike many previous models, the present LB model removes the assumption that the particles have the uniform temperature. Motion of circular catalyst particles in an enclosure is simulated to validate our method. The effect of the thermal expansion coefficient ratio on particle motion behaviours is also investigated.

The artificial island of the Dalian Bay Cross-sea Traffic Engineering Project is the first project in China to use solidified waste dredged soil. The selections of quality control indexes and the suitable silt-cement mixing method for solidified silt island are unclear. We present tests for the curing agent values of different mixing methods, and the compression and permeability characteristics of solidified silt. While the curing agent values for an artificial island is obtained, the selection of mixing method and the primary quality control indicators are discussed, thus providing a reference for similar projects.

Desorption is one of the main factors causing groundwater and soil pollution. Therefore, the study of clay desorption characteristics is important for the prediction of groundwater and soil pollution. In previous studies, batch tests and column tests were used to study the desorption characteristics of pollutants on clay. However, the desorption parameters obtained via the two test methods were often quite different. To investigate differences in the desorption characteristics of different pollutants on clay particles and in compacted clay, batch and column desorption tests were conducted using cadmium chloride, fulvic acid, and sodium phosphate as the adsorbates and bentonite as the adsorbent. It was found that the unit particle surface area desorption distribution coefficients of pollutants on bentonite particles were approximately equal to the unit pore surface area distribution coefficients of pollutants in compacted bentonite. This indicates that the desorbed amount per unit of surface area is basically consistent, regardless of whether they are sorbed on particles or in compacted bentonite. A simple formula for determining the desorption retardation factor of pollutants in compacted bentonite is presented. The results of this study provide a reference for the prediction and evaluation of groundwater and soil pollution.

Sn-based metal-organic framework (MOF) was utilized to effectively capture monophosphopeptides due to the unique affinity. The Sn-based MOF demonstrated the good sensitivity and selectivity in the model phosphoproteins enrichment and was successfully applied in the biological fluids.

A hydrophilic two-dimensional titanium-based metal-organic framework (MOF) nanosheets were prepared and applied to improve the glycopeptides enrichment efficiency. Seventeen N-linked glycopeptides from horseradish peroxidase (HRP) tryptic digests were readily identified and the results showed highly improved signal intensities. As the molar ratio of the mixture of tryptic digests of HRP, glycoprotein (HRP), and nonglycoprotein (BSA) reached 1:800:800, good selectivity of the Ti-MOF nanosheets were still clearly observed. As to human serum samples, 41 glycoproteins and 66 glycopeptides corresponding to 68 N-glycosylation sites were finally detected, which showed the good ability of the nanosheets material to enrich N-linked glycopeptides from complex human serum samples. Moreover, the Ti-MOF nanosheets exhibited unique stability and reusability even after being regenerated and reused for five times. It also performed a high sensitivity (1 × 10−10 M HRP), a good enrichment capacity (250 mg/g) for glycopeptides enrichment and a high enrichment recovery of 78%, suggesting a great application prospect for the enrichment of N-linked glycopeptides and the analysis glycoproteomic research.

In the water treatment process of natural water bodies, a large amount of dredged slurry with high water content is generated and required for treatment. The coagulation–flocculation method can improve the efficiency of separation, and a suitable scheme is of great significance. It is unclear whether there is a significant difference in flocculation and separation of dredged slurries from different sources and which constituents dominate this process. Facing these problems, the tests were conducted for dredged sediments from 10 different sources, including rivers, lake, and ocean. Under the same flocculation conditions, the difference in the increment of particle size d10, the specific resistance of filtration, and the suspended solids (SS) of the supernatant after sedimentation are 0–4.6 times, 0–2.4 orders of magnitude, and 0–4 orders of magnitude, respectively. It was found that the main constituents in the dredged slurries, such as clay minerals, fulvic acid and humic acid, impact on flocculation and separation effects by affecting the zeta potential of the particles. However, there is no single constituent in the dredged slurry which dominates the flocculation and separation effect. When these constituents are incorporated, the zeta potential exhibited in the slurry determines the difference in flocculation and separation effects.

Despite the extensive attention paid to the transport of heavy metals in sludge landfills, the processes of transporting these pollutants from a landfill to the underground environment are quite complicated and subject to significant uncertainty. In this study, the transport of typical heavy metal pollutants in a sludge landfill through saturated and unsaturated soil zones during rainfall was investigated via numerical modeling. The objectives of the study are to evaluate the heavy metal pollution risk from a sludge landfill under rainfall infiltration conditions and to propose several management suggestions. The results indicate that, during rainfall, heavy metal concentrations at the top of the unsaturated sludge layer decrease rapidly, but they decrease more gradually at the bottom of the layer. The maximum concentration appears in vertical distribution and decreases gradually through the saturated zone. Nickel is the first heavy metal pollutant to break through the low-permeability natural silt barrier. The transport parameters not only influence the simulated time for heavy metal pollutants to break through the silt layer and cause underground environmental pollution but also affect the extent to which the heavy metal pollutants in pore water exceed the guidelines. On the basis of these results, for dredged sludge with heavy metal concentrations significantly exceeding the standard, the concentration of heavy metals in pore water should be reduced before the sludge is landfilled, and a covering layer should be established on the sludge surface to control rainfall infiltration.

Balancing domain decomposition by constraints (BDDC) algorithms with adaptive primal constraints are developed in a concise variational framework for the weighted plane wave least-squares (PWLS) discritization of Helmholtz equations with high and various wave numbers. The unknowns to be solved in this preconditioned system are defined on elements rather than vertices or edges, which are different from the well-known discritizations such as the classical finite element method. Through choosing suitable "interface" and appropriate primal constraints with complex coefficients and introducing some local techniques, we developed a two-level adaptive BDDC algorithm for the PWLS discretization, and the condition number of the preconditioned system is proved to be bounded above by a user-defined tolerance and a constant which is only dependent on the maximum number of interfaces per subdomain. A multilevel algorithm is also attempted to resolve the bottleneck in large scale coarse problem. Numerical results are carried out to confirm the theoretical results and illustrate the efficiency of the proposed algorithms.

Two-dimensional (2D) metal-organic framework (MOF) nanosheets, as an emerging type of 2D materials, attract numerous attention due to their unique properties. First, the ultrathin thickness and nanoscale of the materials results in homogeneous dispersion in aqueous solution, giving the materials more opportunities to be utilized in solution chemistry, especially beneficial to the biomimetic catalysis and bio-related analytical applications. Second, the large surface area and accessible active sites of the MOF nanosheets are favorable to the binding between materials and the substrate, leading to their superior performance in catalysis, sensing and enzyme inhibition. Third, the suitable sizes of nanopores on the 2D MOF nanosheets give them the abilities to act as membranes for highly selective and energy-saving gas separation. This minireview covers the synthesis, characterization as well as bio-related and separation applications of 2D MOF nanosheets.

Taxi drivers and passengers are exposed to high levels of traffic-related air pollutants, but their exposures to fine (PM2.5) and ultrafine particles (UFPs) and related mitigation strategies are rarely explored. In this study, UFP and PM2.5 concentrations were monitored concurrently inside and outside of 22 taxis under different ventilation and mitigation conditions. Under realistic working conditions (no mitigation; NM), the average UFP and PM2.5 levels inside taxis were 1.46 × 104 particles/cm3 and 26 μg/m3, respectively. When the taxi ventilation was set to outside air mode and the windows kept closed, in-cabin UFP and PM2.5 concentrations are significantly associated with on-road concentrations, driving speed, and cabin air filter usage. The average in-cabin to on-roadway (I/O) ratios for UFP and PM2.5 were reduced from 0.60 to 0.75 under NM, to 0.47 and 0.52 under the most stringent mitigation strategy of keeping the windows closed and operating a high efficiency cabin air filter (WC + HECA). Among all tested taxi models, Toyota Prius exhibited the lowest UFP and PM2.5 I/O ratios under WC + HECA. Switching cabin air filters from the originally equipped manufacturer filter (OEM) to a HECA filter reduced the UFP and PM2.5 I/O ratios most effectively in Toyota Prius taxis as well.

Groundwater pollution by leachate leakage is one of the most common environmental hazards associated with municipal solid waste (MSW) landfill sites. However, landfill leachate contains a large variety of pollutants with widely different concentrations and biotoxicity. Thus, selecting leachate pollutant indicators and levels for identifying breakthrough of barrier systems are key factors in assessing their breakthrough times. This study investigated the transport behavior of leachate pollutants through landfill barrier systems using centrifuge tests and numerical modeling. The overall objective of this study is to investigate breakthrough mechanism to facilitate the establishment of a consistent pollutant threshold concentration for use as a groundwater pollution alert. The specific objective of the study is to identify which pollutant and breakthrough threshold concentration should be used as an indicator in the transport of multiple pollutants through a landfill barrier system. The threshold concentration from the Chinese groundwater quality standards was used in the analysis of the properties of leachates from many landfill sites in China. The time for the chemical oxygen demand (COD) to reach the breakthrough threshold concentration at the bottom of a 2m compacted clay liner was 1.51years according to centrifuge tests, and 1.81years according to numerical modeling. The COD breakthrough times for single and double composite liners were within the range of 16 and 36.58years. Of all the pollutants, COD was found to consistently reach the breakthrough threshold first. Therefore, COD can be selected as the key indicator for pollution alerts and used to assess the environmental risk posed by MSW landfill sites.

Phosphopeptide enrichment is essential for the phosphoprotein profiling, due to the low abundance in complex biological samples. Moreover, selective binding of multi-phosphopeptides over mono-phosphopeptides is rarely established, but strongly needed in real sample analysis, especially for the investigation of cell behaviors with the multisite phosphorylation cascades. Here two-dimensional (2D) nanosheets were synthesized of Egyptian blue (CaCuSi4 O10 ), the well-known ancient pigment, and its analogues (SrCuSi4 O10 and BaCuSi4 O10 ), which were employed in the enrichment of phosphopeptides for the first time. Surprisingly, the 2D CaCuSi4 O10 nanosheet was highly selective towards multi-phosphopeptides without enriching the mono-phosphorylated peptides in a wide range of acidic conditions or buffer compositions. Meanwhile, the SrCuSi4 O10 and BaCuSi4 O10 nanosheet analogues do not exhibit this unique selectivity. Moreover, the ultrathin and well-defined 2D morphology, with abundant CaII , of Egyptian blue nanosheet was applied in cortical samples of forebrain specific PDK1 conditional knockout mice and their age-matched littermate controls, that are associated with Alzheimer's disease. The as-prepared 2D CaCuSi4 O10 nanosheet not only showed specific selectivity, but also exhibited high sensitivity (detection limit of 4×10-7 m).

A new Semi-Lagrangian scheme is proposed to discretize the surface convection-diffusion equation. The other involved equations including the the level-set convection equation, the re-initialization equation and the extension equation are also solved by S-L schemes. The S-L method removes both the CFL condition and the stiffness caused by the surface Laplacian, allowing larger time step than the Eulerian method. The method is extended to the block-structured adaptive mesh. Numerical examples are given to demonstrate the efficiency of the S-L method.

A detailed theoretical investigation of the interface binding characteristics of Cu(111)/WC(0001) interfaces is studied by first-principles method. The calculation results of the physical properties of Cu and W verify the reliability of our calculation settings. The surface energy calculation results show that the surface of W-termination WC(0001) is the most stable of the two WC(0001) surfaces. The adhesion work of eight W(C)-terminated Cu(111)/WC(0001) interfaces and the interface energy and electronic structures of six stable structures are studied. The results show that bridge site stack interface can be transformed into fcc site stack interface. Among all interface structures, the C-fcc-Cu has the maximum interface adhesion work, while W-hcp-Cu has the minimum interface energy. Analysis of electronic structure reveals that the dominant interfacial bonding is the Cu–W covalent bond and Cu–C covalent bond for the W-termination and C-termination Cu(111)/WC(0001) interface, respectively.

Mechanochromism and mechanoluminescence of a series of fluoro-substituted chiral Pt(N^N^C)Cl complexes have been investigated. With the grafting of F substitutes, the absorption and emission in the solution give an obvious blue-shift. The molecular stacking of solids may also be affected, leading to different mechanochromic and mechanoluminescent behaviors for obtained yellow or orange solid powders of cyclometalated platinum(II) complexes. Remarkably, yellow crystallites of (−)-3FC display a sensitive and contrast mechanochromic and mechanoluminescent phenomenon, with color changing from yellow to orange and luminescence changing from bright green to red (Δλem ≈ 125 nm). The ground solids can be recovered to original crystallites by adding a drop of acetone. Furthermore, the mechanochromic and mechanoluminescent behaviors can be reversible for multiple cycles without perceivable performance degradation.

A three-dimensional (3D) lattice Boltzmann model is proposed to solve 3D natural convection with solid-liquid phase change. The total enthalpy-based thermal lattice Boltzmann model are incorporated in the D3Q19 particle velocity model to handle the temperature field. For the velocity field, the smoothed profile method is applied to implement the no-slip boundary condition at the solid-fluid phase interface. The present method is used to simulate several 3D natural convection problems with solid-liquid phase change, including 3D simulation of melting in a cubical cavity, 3D convection melting in an enclosure with inner rectangle cylinders and solid sphere melting in an cubical enclosure. The 3D effects on the temperature field and phase interface are discussed.

The finite volume methods are frequently employed in the discretization of diffusion problems with interface. In this paper, we firstly present a vertex-centered MACH-like finite volume method for solving stationary diffusion problems with strong discontinuity and multiple material cells on the Eulerian quadrilateral grids. This method is motivated by Frese [No. AMRC-R-874, Mission Research Corp., Albuquerque, NM, 1987]. Then, the local truncation error and global error estimates of the degenerate five-point MACH-like scheme are derived by introducing some new techniques. Especially under some assumptions, we prove that this scheme can reach the asymptotic optimal error estimate O ( h 2 |ln h |) in the maximum norm. Finally, numerical experiments verify theoretical results.

We initially derive an asymptotic expansion and a high accuracy combination formula of the derivatives in the sense of pointwise for the isoparametric bilinear finite volume element scheme by employing the energy-embedded method on some non-uniform grids. Furthermore, we prove that the approximate derivatives are convergent of order two. Numerical examples confirm theoretical results.

In this paper, a free energy-based surface tension force (FESF) model is presented for accurately resolving the surface tension force in numerical simulation of multiphase flows by the level set method. By using the analytical form of order parameter along the normal direction to the interface in the phase-field method and the free energy principle, FESF model offers an explicit and analytical formulation for the surface tension force. The only variable in this formulation is the normal distance to the interface, which can be substituted by the distance function solved by the level set method. On one hand, as compared to conventional continuum surface force (CSF) model in the level set method, FESF model introduces no regularized delta function, due to which it suffers less from numerical diffusions and performs better in mass conservation. On the other hand, as compared to the phase field surface tension force (PFSF) model, the evaluation of surface tension force in FESF model is based on an analytical approach rather than numerical approximations of spatial derivatives. Therefore, better numerical stability and higher accuracy can be expected. Various numerical examples are tested to validate the robustness of the proposed FESF model. It turns out that FESF model performs better than CSF model and PFSF model in terms of accuracy, stability, convergence speed and mass conservation. It is also shown in numerical tests that FESF model can effectively simulate problems with high density/viscosity ratio, high Reynolds number and severe topological interfacial changes. A free energy-based surface tension force (FESF) model is proposed for simulation of multiphase flows by level set method.The proposed model computes the surface tension force by an explicit form.The proposed model outperforms the existing models in terms of accuracy, stability, convergence speed and mass conservation.The proposed model can effectively simulate multiphase flows.

A numerical investigation of natural convection in a Cu–water nanofluid-filled eccentric annulus with constant heat flux wall is presented. The governing equations of the flow and temperature fields are solved by lattice Boltzmann method (LBM), and the Dirichlet and Neumann boundary conditions are treated using the immersed boundary method (IBM). Influences of the Rayleigh number (10 3 ≤ Ra ≤ 10 7 ), eccentricity ( e = −0.625,0 and 0.625), nanoparticles volume fraction (0 ≤ ϕ ≤ 0.03) and radial ratio ( rr = 2.33,2.6 and 3) on the streamlines, isotherms and Nusselt number are studied. It is found that the inclusion of the nanoparticles into pure fluid changes the flow pattern. And the Nusselt number has a positive relationship with nanoparticle volume fraction, Rayleigh number and radial ratio. Also, it can be confirmed that Nusselt number in the case with negative eccentricity ( e = −0.625) is larger than the others.

We present a JASMIN-based two-dimensional parallel implementation of an adaptive combined preconditioner for the solution of linear problems arising in the finite volume discretisation of one-group and multi-group radiation diffusion equations. We first propose the attribute of patch-correlation for cells of a two-dimensional monolayer piecewise rectangular structured grid without any suspensions based on the patch hierarchy of JASMIN, classify and reorder these cells via their attributes, and derive the conversion of cell-permutations. Using two cell-permutations, we then construct some parallel incomplete LU factorisation and substitution algorithms, to provide our parallel -GMRES solver with the help of the default BoomerAMG in the HYPRE library. Numerical results demonstrate that our proposed parallel incomplete LU preconditioner (ILU) is of higher efficiency than the counterpart in the Euclid library, and that the proposed parallel -GMRES solver is more robust and more efficient than the default BoomerAMG-GMRES solver.

A lattice Boltzmann method-immersed boundary method-discrete element method (LBM-IBM-DEM) scheme was presented to simulate the behavior of magnetic particles in a fluid with external magnetic field. In the present scheme, the flow field was solved by the LBM, the DEM with the consideration of the magnetic force was used to describe the particle behavior and the flow field was computed by the momentum exchange-based IBM. Numerical simulations of fluid-particle interactions with uniform magnetic fields in different directions (vertical magnetic field and transverse magnetic field) were carried out to study the particle motion and hydrodynamic behavior in details. The numerical results indicated that the external magnetic force has a significant influence on the particle behavior, where some fragmented chains along the direction are formed and these chain-like clusters continue to lengthen, align, and approach an almost steady state. In addition, we also studied the effect of the magnetic field strength on the motion of magnetic particles showing that in the same particle system, stronger magnetic field brings magnetic particles greater kinetic energy than the low density magnetic field does.

The Wenzel roughness factor r is one of the most important parameters to characterize a super-hydrophobic surface. In this study, in order to prove the feasibility of using laser scanning confocal microscopy (LSCM) to measure the roughness factor r, the detected r values by LSCM on texture-regular surfaces were compared with those calculated firstly, and then the r values measured by LSCM for texture-irregular rough surfaces were compared with those measured by AFM. The results show that the r values of texture-regular surfaces measured by LSCM are close to those calculated, and the LSCM measured r values of texture-irregular surfaces with small roughness are consistent with those measured by AFM. Moreover, the r values of texture-irregular surfaces with large roughness can only be measured by LSCM, the detected r values of three such super-hydrophobic surfaces are 2.13 ± 0.01, 2.12 ± 0.01 and 2.13 ± 0.02, respectively. In addition, it is proved that the r measured by LSCM as a line length ratio is equal to the original definition of roughness factor as the ratio of actual area of solid surface to the horizontal projected area. Consequently, it is reliable to measure the r value of a texture-irregular surface with large roughness in micro or submicro scale by LSCM.

A multiple-relaxation-time (MRT) lattice Boltzmann (LB) model is proposed for simulating flow and heat transfer in the hydrodynamically and thermally anisotropic porous medium at the representative-elementary-volume (REV) scale. By selecting the appropriate equilibrium distributions, relaxation matrix and discrete force/heat source terms, the present MRT LB model can recover the correct Darcy–Brinkman–Forchheimer and energy equations with anisotropic permeability and thermal conductivity through the Chapman–Enskog procedure. Several natural convection problems in anisotropic porous medium are simulated to validate the present LB model. The corresponding numerical results are in good agreement with data in the available literature. Especially, natural convection in a cavity with two anisotropic porous layers is investigated. The numerical results indicates that, the use of anisotropic porous layer with some optimal parameters can produce higher rate of heat transfer compared with the isotropic porous layer.

The multigrid-reduction-in-time (MGRIT) technique has proven to be successful in achieving higher run-time speedup by exploiting parallelism in time. The goal of this article is to develop and analyze a MGRIT algorithm, using FCF-relaxation with time-dependent time-grid propagators, to seek the finite element approximations of unsteady fractional Laplacian problems. The multigrid with line smoother proposed in [L. Chen, R. H. Nochetto, E. Ot{\'a}rola, A. J. Salgado, Math. Comp. 85 (2016) 2583--2607] is chosen to be the spatial solver. Motivated by [B. S. Southworth, SIAM J. Matrix Anal. Appl. 40 (2019) 564--608], we provide a new temporal eigenvalue approximation property and then deduce a generalized two-level convergence theory which removes the previous unitary diagonalization assumption on the fine and coarse time-grid propagators required in [X. Q. Yue, S. Shu, X. W. Xu, W. P. Bu, K. J. Pan, Comput. Math. Appl. 78 (2019) 3471--3484]. Numerical computations are included to confirm the theoretical predictions and demonstrate the sharpness of the derived convergence upper bound., Comment: 17 pages, 4 figures

Evaluation of adsorption properties of pollutants on artificial or natural clay strata is normally considered in investigations of soil and groundwater pollution. Batch adsorption tests can be used to obtain the adsorption parameters of clay particles; however, the results from these tests are usually very different from the adsorption of actual clay strata. If the adsorption parameters obtained by batch tests are used to directly evaluate the properties of adsorption of pollutants onto compacted clay, the predicted groundwater and soil pollution will be unsafe. Although the column diffusion tests are closer to the actual situation, they may require much more time, and diffusion and adsorption occur simultaneously in tests, making it difficult to accurately determine the adsorption parameters. To solve this problem, batch adsorption and column diffusion tests were conducted using three kinds of clay materials to investigate the mechanism of the differences in adsorption properties of heavy metal on clay particles and in compacted clay. The amount of adsorption per unit particle surface area of clay particles was found to be equal to that per unit pore surface area of compacted clay. A new simplified method was proposed to determine the adsorption parameters in compacted clay. It is easy to use and provide a reference for prediction and evaluation of soil and groundwater pollution.

In this work a phase field-lattice Boltzmann model for incompressible two-phase flows is presented. In this model, the interface tracking equation is a linear combination of the local and nonlocal Allen-Cahn equations. We also propose a multiple-relaxation-time lattice Boltzmann model for solving the hybrid Allen-Cahn equation. The second-order convergence rate of the present model in space is validated by simulating the diagonal translation of circular interface. Three other numerical tests, including static bubble immersed in another fluid, bubble rising under gravity, and droplet splashing on a thin liquid film, are simulated to verify the performance of the present model in reducing the numerical dispersion. The numerical results indicate that the order parameter fluctuation can be reduced by one order of magnitude in bulk region.

Using sewage sludge as temporary cover for landfills is one of the most effective methods to dispose sludge. The mechanical properties of solidified sludge usually meet the requirements for temporary landfill cover, but its low permeability can cause problems due to formation of perched leachate. This study focused on the effect of solidification and remolding on hydraulic conductivity of sludge and conducted permeability tests on sludge solidified by using either ordinary Portland cement (OPC) or sulphoaluminate cement (SAC). The related pore structure and aggregate size distribution were analyzed later by the mercury intrusion pressure (MIP) method and soil water characteristic cure (SWCC) method. The experiment results show that the hydraulic conductivity of solidified sludge was in the range of 10−7∼10−6 cm/s. When sludge is solidified with an SAC dosage >40% and remolded after curing for 7 days, its hydraulic conductivity increases sufficiently to the order of 10−4 cm/s. The trend for solidified sludge exhibited a power function relation between the logarithmic hydraulic conductivity and the proportion of macropores. Overall, it can be concluded that the increase of hydraulic conductivity is attributed to the development of an aggregate structure, with water being transmitted mainly through the interaggregate pores; therefore, the sludge could be used as temporary landfill cover.

In this paper, in order to study the dissipativity of nonlinear neutral functional differential equations, a generalization of the Halanay inequality is given. We apply this generalized Halanay inequality to an analysis of the dissipativity of two classes of nonlinear neutral delay integro-differential equations and the sufficient conditions are presented to ensure these systems are dissipative.

Two roads diverged in a yellow photolyase Photolyase enzymes repair DNA that has been damaged by ultraviolet sunlight. The repair process begins when blue light absorption by a cofactor drives an electron transfer step. Zhang et al. applied ultrafast absorption spectroscopy to study the dynamics of this step. A bifurcation in the electron transfer pathway favors a direct tunneling mechanism in the prokaryotic enzymes and a two-step hopping mechanism in the eukaryotic variety. This difference explains the higher repair quantum yield seen in prokaryotes. Science , this issue p. 209

Semi-Lagrangian (S-L) methods have no CFL stability constraint, and are more stable than the Eulerian methods. In the literature, the S-L method for the level-set re-initialization equation was complicated, which may be unnecessary. Since the re-initialization procedure is auxiliary, we propose to use the first-order S-L scheme coupled with a projection technique to improve the accuracy at the grid points just adjacent to the interface. Standard second-order S-L method is used for evolving the level-set convection equation. The implementation is simple, including on the block-structured adaptive mesh. The efficiency of the S-L method is demonstrated by extensive numerical examples including passive convection of interfaces with corners/kinks/large deformation under given velocity fields, a geometrical flow with topological changes, simulations of bubble/ droplet dynamics in incompressible two-phase flows. In terms of accuracy it is comparable to the other existing methods.

In this work a lattice Boltzmann flux scheme for the convection-diffusion equation (CDE) is proposed. In this scheme, the fluxes across the cell interface are calculated by using the local solution of the multiple-relaxation-time lattice Boltzmann equation for CDE. The present method is suitable for simulating both isotopic and anisotropic diffusion processes. Meanwhile, through applying the midpoint time integration technique, the present method relaxes the time step constraint in the original lattice Boltzmann flux scheme. Four convection-diffusion problems are simulated to validate the present scheme. The obtained results agree well with the analytical or previous published solutions.

Emissions from electronic cigarettes (ECs) may contribute to both indoor and outdoor air pollution and the number of users is increasing rapidly. ECs operate based on the evaporation of e-liquid by a high-temperature heating coil. Both puff topography and design parameters can affect this evaporation process. In this study, both mainstream aerosols and heating coil temperature were measured concurrently to study the effects of design parameters and puff topography. The heating coil temperatures and mainstream aerosols varied over a wide range across different brands and within same brand. The peak heating coil temperature and the count median diameter (CMD) of EC aerosols increased with a longer puff duration and a lower puff flow rate. The particle number concentration was positively associated with the puff duration and puff flow rate. These results provide a better understanding of how EC emissions are affected by design parameters and puff topography and emphasize the urgent need to better regulate EC products.