聚丙烯/改性二氧化钛纳米复合纤维的制备及其在煤化工废水处理中的应用

以二氧化钛为原料制备了改性二氧化钛(m@TiO_(2)),然后以其为助剂通过熔喷非织造技术制备了聚丙烯/m@TiO_(2)纳米复合纤维膜。通过正交实验确定了其最优制备工艺条件为,热风温度为295℃、热风压力为400 kPa、料筒压力为400 kPa。对聚丙烯/m@TiO_(2)纳米复合纤维膜的结构和热性能进行了表征,并研究了其在煤化工废水中的应用。结果表明,PP5纳米复合纤维膜的结晶度为37.6%,孔隙率为96.3%,纤维平均直径为3.8μm,且具有较高的热稳定性。在pH=3、温度为45℃、吸附时间50 min时,测试了PP1与PP5对煤化工废水吸附处理降低化学需氧量(COD)值。结果表明,PP5对COD的去除率达到了20.1%,远高于PP1(COD的去除率11.1%)。25℃下经过光催化降解后,PP5对COD的去除率达到82.5%,表明PP5具有优异的光催化降解煤化工废水中有机物的性能,并且PP5对煤化工废水中有机物的光降解反应符合一级动力学模型。聚丙烯/m@TiO_(2)纳米复合纤维膜对降低煤化工废水中的COD表现出良好的应用前景。

Distributed Lagrange Multiplier/Fictitious Domain Finite Element Method for a Transient Stokes Interface Problem with Jump Coefficients

The distributed Lagrange multiplier/fictitious domain(DLM/FD)-mixed finite element method is developed and analyzed in this paper for a transient Stokes interface problem with jump coefficients.The semi-and fully discrete DLM/FD-mixed finite element scheme are developed for the first time for this problem with a moving interface,where the arbitrary Lagrangian-Eulerian(ALE)technique is employed to deal with the moving and immersed subdomain.Stability and optimal convergence properties are obtained for both schemes.Numerical experiments are carried out for different scenarios of jump coefficients,and all theoretical results are validated.

An Augmented Lagrangian Uzawa IterativeMethod for Solving Double Saddle-Point Systems with Semidefinite(2,2)Block and its Application to DLM/FDMethod for Elliptic Interface Problems

.In this paper,an augmented Lagrangian Uzawa iterative method is developed and analyzed for solving a class of double saddle-point systems with semidefinite(2,2)block.Convergence of the iterativemethod is proved under the assumption that the double saddle-point problem exists a unique solution.An application of the iterative method to the double saddle-point systems arising from the distributed Lagrange multiplier/fictitious domain(DLM/FD)finite element method for solving elliptic interface problems is also presented,in which the existence and uniqueness of the double saddle-point system is guaranteed by the analysis of the DLM/FD finite element method.Numerical experiments are conducted to validate the theoretical results and to study the performance of the proposed iterative method.

Numerical Study of a 3D Two-Phase PEM Fuel Cell Model Via a Novel Automated Finite Element/Finite Volume Program Generator

Numerical methods of a 3D multiphysics,two-phase transport model of proton exchange membrane fuel cell(PEMFC)is studied in this paper.Due to the coexistence of multiphase regions,the standard finite element/finite volume method may fail to obtain a convergent nonlinear iteration for a two-phase transport model of PEMFC[49,50].By introducing Kirchhoff transformation technique and a combined finite element-upwind finite volume approach,we efficiently achieve a fast convergence and reasonable solutions for this multiphase,multiphysics PEMFC model.Numerical implementation is done by using a novel automated finite element/finite volume programgenerator(FEPG).By virtue of a high-level algorithmdescription language(script),component programming and human intelligence technologies,FEPG can quickly generate finite element/finite volume source code for PEMFC simulation.Thus,one can focus on the efficient algorithm research without being distracted by the tedious computer programming on finite element/finite volume methods.Numerical success confirms that FEPG is an efficient tool for both algorithm research and software development of a 3D,multiphysics PEMFC model with multicomponent and multiphase mechanism.

Fast Numerical Simulation of Two-Phase Transport Model in the Cathode of a Polymer Electrolyte Fuel Cell

In this paper,we apply streamline-diffusion and Galerkin-least-squares fi-nite element methods for 2D steady-state two-phase model in the cathode of polymer electrolyte fuel cell(PEFC)that contains a gas channel and a gas diffusion layer(GDL).This two-phase PEFC model is typically modeled by a modified Navier-Stokes equation for the mass and momentum,with Darcy’s drag as an additional source term in momentum for flows through GDL,and a discontinuous and degenerate convectiondiffusion equation for water concentration.Based on the mixed finite element method for the modified Navier-Stokes equation and standard finite element method for water equation,we design streamline-diffusion and Galerkin-least-squares to overcome the dominant convection arising from the gas channel.Meanwhile,we employ Kirchhoff transformation to deal with the discontinuous and degenerate diffusivity in water concentration.Numerical experiments demonstrate that our finite element methods,together with these numerical techniques,are able to get accurate physical solutions with fast convergence.

Predict Blood Pressure by Photoplethysmogram with the Fluid-Structure Interaction Modeling

Blood pressure(BP)has been identified as one of the main factors in cardiovascular disease and other related diseases.Then how to accurately and conveniently measure BP is important to monitor BP and to prevent hypertension.This paper proposes an efficient BP measurement model by integrating a fluid-structure interaction model with the photoplethysmogram(PPG)signal and developing a data-driven computational approach to fit two optimization parameters in the proposedmodel for each individual.The developed BPmodel has been validated on a public BP dataset and has shown that the average prediction errors among the root mean square error(RMSE),the mean absolute error(MAE),the systolic blood pressure(SBP)error,and the diastolic blood pressure(DBP)error are all below 5mmHg for normal BP,stage I,and stage II hypertension groups,and,prediction accuracies of the SBP and the DBP are around 96%among those three groups.

Phase Field Model of Thermo-Induced Marangoni Effects in the Mixtures and its Numerical Simulations with Mixed Finite Element Method

In this paper,we study the Marangoni effects in the mixture of two Newtonian fluids due to the thermo-induced surface tension heterogeneity on the interface.We employ an energetic variational phase field model to describe its physical phenomena,and obtain the corresponding governing equations defined by a modi-fied Navier-Stokes equations coupled with phase field and energy transport.A mixed Taylor-Hood finite element discretization together with full Newton’s method are applied to this strongly nonlinear phase field model on a specific domain.Under different boundary conditions of temperature,the resulting numerical solutions illustrate that the thermal energy plays a fundamental role in the interfacial dynamics of two-phase flows.In particular,it gives rise to a dynamic interfacial tension that depends on the direction of temperature gradient,determining the movement of the interface along a sine/cosine-like curve.