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Partial denitrification(PD) can reduce nitrate to nitrite, and is an important way to provide substrates steadily in anaerobic ammonia oxidization(ANAMMOX) reaction. PD has great potential in energy-efficient biological nitrogen removal of wastewater, and has become a research hotspot in recent years. In this work,the mechanism of PD was introduced from the aspects of its biological process and functional microorganisms. Then the key factors affecting the PD process, such as carbon source, carbon-nitrogen ratio, environmental conditions, and heavy metals, etc. were summarized. Moreover, the research on PD in biological nitrogen removal process in recent years was also reviewed. Finally, the problems existing in the current research and the aspects for further research of PD were discussed. This work is expected to provide theoretical supports for the development and application of PD in biological nitrogen removal of wastewater.

A strain D5 with excellent partial denitrification performance was screened from paddy soil. The bacteria were identified as Klebsiella pneumoniae by morphological observation and 16S r DNA sequence analysis. The denitrification ability of strain D5 under different environmental factors （carbon source，C/N ratio and temperature） were investigated using single-factor experiments. The results showed that various environmental factors had obvious influence on partial denitrification of strain D5. The optimal conditions for partial denitrification activity of strain D5 were carbon source of sodium citrate， C/N ratio of 3，temperatures of 25 ℃ and 35 ℃. The results showed that strain D5 had excellent partial denitrification performance，and the optimal partial denitrification effect could be achieved by regulating environmental conditions.

A series of nematic liquid crystal (LC) monomers, containing a reactive group in the lateral substituent, were designed and synthesised through an organic synthesis reaction. Considerable changes were made to the properties of the liquid monomers by varying the terminal alkyl chain lengths. The molecular structures of the intermediates and the LC monomers were characterised by flourier infrared absorption spectrometry and proton nuclear magnetic resonance (1H NMR) spectroscopy, leading to the identification of the target product. The phase transition temperatures of the LC monomers were observed and analysed using differential scanning calorimetry (DSC) and polarising optical microscopy (POM) with a hot stage. The two-way thermotropic liquid crystalline behaviour was observed during the heating process, providing insight into the effect of substituent changes on the phase transition temperature. [ABSTRACT FROM AUTHOR]

In this paper, two efficient high-order physical property-preserving linearly implicit finite difference schemes are firstly developed and analyzed for nonlinear fourth-order wave equation with damping based on the scalar auxiliary variable (SAV) approach and newly developed Lagrange multiplier (LM) approach, respectively. Then the modified energy preservation property, the priori bounds of the numerical solution and convergence analysis of the former scheme are presented in detail. It is pointed out that the former scheme only conserves/dissipates the modified discrete energy, not the original energy while the latter scheme conserves/dissipates the original discrete energy exactly. Also, the latter scheme only demands to solve a decoupled and linear system with constant coefficients at each time step plus a nonlinear algebraic system. Finally, some numerical simulations are presented to demonstrate the accuracy, efficiency and preservation property of the obtained schemes. • Two efficient physical property-preserving difference methods for the nonlinear fourth-order wave equation with damping are proposed. • The modified preservation property and error estimation of the former scheme are presented in detail. • Both schemes demand to solve a sequence of linear decoupled systems with constant coefficients at each time step. • Some numerical results are performed to demonstrate the accuracy, efficiency and preservation property of both schemes. [ABSTRACT FROM AUTHOR]

This paper concentrates on the error estimation of novel time second‐order splitting conservative finite difference method (FDM) for high‐dimensional nonlinear fractional Schrödinger equation rigorously. The discrete preservation property of our scheme is exhibited. By virtue of the cut‐off technique and discrete energy method, it is shown that our scheme possesses the accuracy of O(Δt2+hx2+hy2) in sense of L2‐ norm. Numerical experiments are exhibited to validate the accuracy and conservation property of our scheme. [ABSTRACT FROM AUTHOR]

In this work, a spherical Sn-MOF precursor was synthesized through hydrothermal method using 1,3,5-benzenetricarboxylic acid (H3BTC) as the organic ligand. Sn-MOF-200, Sn-MOF-250, and Sn-MOF-300 were obtained at different annealing temperatures. Among them, the Sn-MOF-250 composite obtained by annealing at 250 ℃ was stable in structure, and the specific surface area is 118.8 m2 g−1. The specific capacity of Sn-MOF-250 can be maintained up to 846.6 mA h g−1 after 110 cycles at the current density of 100 mA g−1 when used as the anode material of lithium-ion battery. The excellent cycling performance of Sn-MOF-250 is due to the special framework structure of metal–organic frameworks (MOFs). After combining with Sn ion, the metal–organic coordination compound formed can greatly improve the diffusion and transport efficiency of lithium ion. This facile synthesis strategy has a certain application prospect in the development of high-performance lithium-ion battery anode materials. [ABSTRACT FROM AUTHOR]

In this paper, we present a nonconforming immersed finite element method for solving elliptic optimal control problems with interfaces. The immersed finite element space is constructed based on the rotated-Q1 nonconforming finite elements with the integral-value degrees of freedom. The method can overcome the difficulties encountered by conforming immersed finite element method. We derive error estimates for the control, state and adjoint state in both energy and L 2 norms. Numerical results are reported to support the theoretical analysis. [ABSTRACT FROM AUTHOR]

• It is difficult to develop efficient conservative difference schemes for space fractional Klein-Gordon-Zakharov system. • New auxiliary equations are introduced to transform the original fractional system into the equivalent system of equations. • Two novel linearly implicit conservative difference schemes for the transformed system are developed and analyzed. • The discrete energy conservation properties, unconditional convergence of the suggested schemes are proved rigidly. • Numerical results are exhibited to study the physical behavior of the wave propagation and confirm efficiency of schemes. In this article, novel linearized implicit difference schemes with energy conservation property for fractional Klein-Gordon-Zakharov system are constructed and analyzed. The important feature of the article is that new auxiliary equations ∂ u ∂ t = − v and ∂ ϕ ∂ t = ∂ 2 ψ ∂ x 2 are introduced to transform the original fractional Klein-Gordon-Zakharov system into an equivalent system of equations exactly. Especially, two kinds of efficacious difference operators, the leap-frog and modified Crank-Nicolson methods are respectively utilized to establish the linearized implicit difference schemes with energy conservation property for simulating the propagation of transformed equations. And above all, by employing the discrete energy method, we have proven that the constructed difference algorithms enjoy the convergence order of O (Δ t 2 + h 2) and O (Δ t 2 + h 4) in L ∞ - and L 2 -norms, without imposing any restrictive conditions on the grid ratio compared with the existing literature. Two numerical examples are carried out to investigate the physical behaviors of the wave propagation and substantiate the effectiveness of the suggested schemes. [ABSTRACT FROM AUTHOR]

In this paper, a new bilinear immersed finite volume element method based on rectangular mesh is presented to solve the elliptic interface problems with non-homogeneous jump conditions and sharp-edged interfaces. This method is capable of dealing with the case when the interface passes through grid points and when the solutions are oscillating. Plenty of numerical experiments show that our method is nearly second-order accuracy for the solution and is first-order accuracy for the gradient of the solution in the L ∞ norm. • The proposed bilinear IFVE method can deal with the case when the solution or its normal derivative is discontinuous. • Numerical results demonstrate that the method is second-order accuracy for the solution in the L ∞ norm. • The new method can solve the crack problem provided that the mesh is fine enough. [ABSTRACT FROM AUTHOR]

Thin film composite (TFC) reverse osmosis (RO) membranes with high permeability have been prepared by interfacial polymerization based on tailoring the polysulfone (PSf) substrate structure by in situ embedded poly(p‐phenylene terephthamide) (PPTA) star‐like rigid supports. The star‐like rigid supports were observed by the polarizing optical microscopy (POM) and transmission electron microscope (TEM). The surface properties of the substrates were investigated by FTIR, the water contact angle (WCA), FESEM and AFM. The WCA was decreased from 88.5° to 72.3° with the PPTA increasing from 0% to 8%, and the surface roughness increased from 24.2, 25.1, 33.5 and 58.6 nm, respectively. Furthermore, numerous interconnect micro‐structures were constructed in the substrate when the PPTA content was up to 8%. The pure water flux of 8% PPTA/92%PSf substrate was up to 377.0 L m−2 h−1 and the flux decline rate was lowest (64%) after compacted at 5.5 MPa for 30 min. Otherwise, increasing the PPTA contents in the substrate enhanced the roughness, encouraged nanosheet formation and improved the permeability of TFC RO membranes. The pure water flux of the TFC RO membranes increased from 36.32 to 58.42 L m−2 h−1, where the NaCl rejection was about 99.5% at 5.5 MPa. [ABSTRACT FROM AUTHOR]

• Unconditionally convergent energy dissipative numerical methods are developed and analyzed for nonlinear wave equations. • Two novel efficient energy dissipative difference schemes for the wave equations are first set forth and analyzed. • The discrete energy dissipation properties, solvability, unconditional convergence and stability results are proven rigidly. • Some numerical results are provided to illustrate the computational accuracy and efficiency of the proposed schemes. In this paper, two new efficient energy dissipative difference schemes for the strongly coupled nonlinear damped space fractional wave equations are first set forth and analyzed, which involve a two-level nonlinear difference scheme, and a three-level linear difference scheme based on invariant energy quadratization formulation. Then the discrete energy dissipation properties, solvability, unconditional convergence and stability of the proposed schemes are exhibited rigidly. By the discrete energy analysis method, it is rigidly shown that the proposed schemes achieve the unconditional convergence rates of O (Δ t 2 + h 2) in the discrete L ∞ -norm for the associated numerical solutions. At last, some numerical results are provided to illustrate the dynamical behaviors of the damping terms and unconditional energy stability of the suggested schemes, and testify the efficiency of theoretical results. [ABSTRACT FROM AUTHOR]

Novel microspheres (CPs) composited by rigid and flexible polymers are synthesized and embedded in the supporting membranes to enhance both the skin–substrate adhesion and compaction resistance of the thin‐film composite (TFC) nanofiltration membranes. The CPs are in situ formed in the casting solution after the rigid poly(p‐phenylene terephthamide) (PPTA) is produced in the flexible poly(m‐phenylene isophthalamide) (PMIA) solution. Then the PPTA/PMIA in situ blending membranes are prepared by using the NIPs method, and the TFC NF membranes are fabricated via interfacial polymerization on them. The CPs are characterized via polarizing microscopy and TEM. The surface morphology and chemical composition of the blended membranes are characterized by using FESEM, AFM, FTIR, and WCA, respectively. As the results show, the supporting membrane with higher PPTA content exhibits higher permeability, thermal stability, and compaction resistance. Moreover, the adhesion strength between the TFC functional layer and the supporting membrane is improved significantly. It is proposed that this improvement can be attributed to the CPs that are exposed on the top surface of the supporting membrane, which leads to a great enhancement because of the anchoring effect between the functional layer and the CPs. [ABSTRACT FROM AUTHOR]

In this paper, by applying order reduction approach, a second-order accurate box scheme is established to solve a nonlinear delayed convection-diffusion equations with Neumann boundary conditions. By the discrete energy method, it is shown that the difference scheme is uniquely solvable, and has a convergence rate of with respect to - norm in constrained and non-constrained temporal grids. Besides, for constrained temporal step, a Richardson extrapolation method (REM) used along with the box scheme, which makes final solution third-order accurate in both time and space, is developed in detail. Finally, numerical results confirm the accuracy and efficiency of our solvers. [ABSTRACT FROM AUTHOR]

• The existence of energy invariant for the fractional BE is derived. • An energy-preserving splitting CN scheme for the fractional BE is established. • A new potential function is introduced to ensure the conservation of energy. • Discrete energy property, convergence and unconditional stability are proved. In this paper, an efficient energy-preserving splitting Crank-Nicolson difference scheme for the fractional-in-space Boussinesq equation is established. The novelty of the proposed scheme here is that the potential function v is introduced via ∂ u ∂ t = − (− Δ) α 2 v to ensure the conservation of energy. By utilizing the discrete energy method, it is shown that the proposed scheme attains the convergence rates of O (Δ t 2 + h 2) in the discrete L ∞ -norm without any restrictions on the grid ratio, and is unconditionally stable. Finally, a linearized iterative algorithm is proposed and numerical results are provided to demonstrate the correctness of the theoretical results. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we propose an efficient linearly implicit conservative difference solver for the fractional Klein–Gordon–Zakharov system. First of all, we present a detailed derivation of the energy conservation property of the system in the discrete setting. Then, by using the mathematical induction, it is proved that the proposed scheme is uniquely solvable. Subsequently, by virtue of the discrete energy method and a 'cut-off' function technique, it is shown that the proposed solver possesses the convergence rates of O (Δ t 2 + h 2) in the sense of L ∞- and L 2- norms, respectively, and is unconditionally stable. Finally, numerical results testify the effectiveness of the proposed scheme and exhibit the correctness of theoretical results. [ABSTRACT FROM AUTHOR]

Three kinds of end group with double bonds (IVm) were synthesized by esterification reaction, etherification reaction and hydrolysis reaction, using methyl 4-hydroxybenzoate as the main raw material. And the double bonds were oxidized by 3-chloroperoxybenzoic acid as an oxidizing agent to get three kinds of epoxy-functional groups liquid crystal monomers (Vm). The molecular structures of the liquid crystal monomers were characterized by Fourier infrared absorption spectrometer (FT-1R) and proton nuclear magnetic resonance (NMR) spectroscopy, and the target product was identified. The performance of the product was characterized by differential scanning calorimetry (DSC) and thermal polarizing microscope (POM). The results shows that all the products were with the correct molecular structure and had liquid crystal properties under certain conditions with enantiotropic nematic mesophase. [ABSTRACT FROM AUTHOR]

In this paper, a compact difference scheme is established for nonlinear delayed fractional sub-diffusion equations. By the discrete energy method, it is shown that it achieves the convergence rate ofinL∞- norm, and is unconditionally stable. Here,αis the order of fractional derivative. Besides, the extension of the solver to multi-term time fractional sub-diffusion equations with delays is discussed. Finally, numerical results demonstrate the effectiveness of our solvers. [ABSTRACT FROM PUBLISHER]

Graphene oxide was reduced into reducing-graphene oxide (r-GO) successfully using gallic acid (GA) as a green reducing agent. Biobased gallic acid epoxy resin (GAER) was synthesized from renewable GA, and the biobased GAER/r-GO nanocomposites and glass fiber-reinforced composites were prepared with succinic anhydride as a curing agent. The dynamic mechanical, thermal, and mechanical properties of the composites with varying r-GO contents were characterized. When the content of r-GO was 0.5 wt%, the glass transition temperature was 10.4°C higher than the pure resin system. The thermal and mechanical properties were increased with increasing r-GO content; when the r-GO content was 1.0 wt%, the initial degradation temperature was enhanced by approximately 6.8°C, the tensile and impact strengths were 34.5% and 49.1% higher, respectively, than the pure cured GAER. The impact strength of GAER was higher than that of the bisphenol A epoxy resin/SUA curing system, but the tensile strength was lower than it. [ABSTRACT FROM AUTHOR]

A new series of liquid crystal (LC) monomers – not only contain a double bond but also contain an azo group – were designed and synthesised. The length of side groups in the LC monomers containing azobenzene ester varied from 1 to 2 methylene units, and the length of the substituted groups in the main chain varied from 1 to 3 methylene units. The molecular structures of the intermediates and target compounds were confirmed by Fourier transform infrared, ultraviolet and visible spectrum and nuclear magnetic resonance (NMR) spectroscopy. The thermal phase behaviour of the LC monomers was investigated by polar optical microscopy coupled with hot stage and differential scanning calorimetry (DSC). In this paper, the effect on the LC zone with the substituents were investigated, and with the increased methylene of main chain, the melting point and the phase transition temperature of the substance will be lowered and LC regions will be narrower. [ABSTRACT FROM AUTHOR]

A new series of nematic liquid crystal (LC) monomers containing double bonds in the side chain were designed and synthesized via the Steglich esterification reaction. Length of the side groups varied from 1 to 2 methylene units. The molecular structures of the intermediates and the LC monomers were confirmed by Fourier transform infrared spectrum, elemental analysis, and nuclear magnetic resonance spectroscopy. The thermal phase behavior of the LC monomers was investigated by differential scanning calorimetry and polar optical microscopy coupled with hot stage. All of these LC monomers showed only one nematic mesophase at room temperature during the cooling process. [ABSTRACT FROM PUBLISHER]

Two nematic liquid crystal (LC) monomers containing double bonds in the side chain were designed and synthesised. Length of the side groups varied from 1 to 2 methylene units. The side-chain polymers were synthesised by hydrosilylation reaction. The molecular structures of the intermediates and the LC monomers were characterised by Fourier transform infrared, elemental analysis and nuclear magnetic resonance spectroscopy. The thermal phase behaviour of the monomers and polymers were investigated by differential scanning calorimetry and polar optical microscopy coupled with hot stage. The LC monomers showed only one nematic mesophase in the cooling process. And, the two polymers exhibit an enantiotroppic nematic mesophase either in the heating or in the cooling process. [ABSTRACT FROM AUTHOR]

• Bio-based p-coumaric acid epoxy resin (HCA-EP) and new fluorinated diamine curing agent (BAFFP) were synthesized. • When 30 wt% BAFFP was added, the impact and flexural strength of HCA-EP were increased by 147% and 26%, respectively. • When 30 wt% BAFFP was added, HCA-EP has excellent dielectric properties (D k = 3.61 and D f = 0.00239 at 10 MHz). • HCA-EP-BAFFP can meet the demand for use as a potential electronic material. The epoxy resin based on p-coumaric acid and fluorine-containing diamine curing agent based on bisphenol AF were synthesized. The chemical structure was confirmed by FTIR, 1H NMR, 13C NMR and 19F NMR. Using HCA-EP as the epoxy resin matrix, methyl hexahydro phthalic anhydride as the curing agent and BAFFP as the co-curing agent, the performance differences were investigated for different curing systems, including HCA-EP-BAFFP-0/10/20/30. The results show that the increase of BAFFP content can improve the mechanical properties and dielectric properties of HCA-EP. In particular, HCA-EP-BAFFP-30 exhibited the highest impact and flexural strengths (7.14 KJ/m2 and 142 MPa), exceeding HCAP-EP-BAFFP-0 (2.9 KJ/m2 and 113 MPa) by 147% and 26%. In addition, HCA-EP-BAFFP-30 has the lowest dielectric constant and dielectric loss (D k = 3.61 and D f = 0.00243 at 10 MHz). Therefore, we believe that HCA-EP cured with BAFFP has great potential for application in the field of electronic packaging materials. [ABSTRACT FROM AUTHOR]

• A p-hydroxycinnamic acid-derived epoxy resin monomer (HCA-EP) was developed. • Sustainable preparation of fluorine-containing bio-based epoxy resin system. • Excellent flame-retardant properties were obtained. • Improved mechanical, dielectric, hydrophobic properties of bio-based epoxy resins. Epoxy resins are designed to achieve high flame retardancy, hydrophobicity, and dielectric properties. However, the search for sustainable bio-based epoxy resin precursors that do not require additional flame retardants is still underway. Herein, we report a p-hydroxycinnamic acid-derived epoxy resin monomer (HCA-EP) obtained via a simple one-step reaction. HCA-EP can be combined with 4,4′-((2,2′-bis(trifluoromethyl)-[1,1′- biphenyl ]-4,4′-dial)bis(azanylylidene))bis(methanylylidene))bis(2,6-dimethoxyphenol) (SA-BTB) and cured to prepare epoxy resins(HCA-EP/SA-BTB). In comparison to HCA-EP cured with a common petroleum-based curing agent(HCA-EP/MeHHPA), such as methylhexahydrophthalic anhydride (MeHHPA), HCA-EP/SA-BTB exhibited a significantly high glass transition temperature (170 °C), excellent hydrophobic properties, and lower dielectric loss. In addition, HCA-EP/SA-BTB passed the V-0 flame rating of the UL-94 test and exhibited an ultimate oxygen index of 43.3%. Notably, it demonstrated a coke yield of 42.3% under N 2 conditions, whereas that of HCA-EP/MeHHPA was 18%. Moreover, its flame-retardant index was found to be 19.8, indicating its excellent flame-retardant properties. Further, it could be degraded under acidic conditions. These findings indicate that the proposed method can be used to develop high-performance bio-based thermoset materials. [ABSTRACT FROM AUTHOR]