基于SRB的升流式厌氧反应器处理AMD的探究

在矿山开采过程中产生的酸性矿山废水(AMD)具有pH低、重金属离子和硫酸根离子浓度大等特点,处理不当会导致严重的环境污染问题。以硫酸盐还原菌(SRB)为主的生物法是一种极具应用前景的技术。通过填充活性炭的升流式厌氧反应器,对120 d的连续流实验中SO_(4)^(2-)和重金属的还原效果进行了研究。结果表明,该升流式厌氧反应器对模拟AMD中的SO_(4)^(2-)和重金属具有很好的处理效果,在SO_(4)^(2-)、Cu^(2+)、Mn^(2+)、Fe^(2+)、Cd^(2+)进水浓度分别为1000、3、6、30、2 mg/L,去除率可达85%、92%、86%、80%、100%。运行过程中该反应器的ORP始终低于-420 mV,为SRB提供良好的厌氧环境。同时,该SRB菌群能适应进水pH为5.5的酸性废水,可顺利完成硫酸盐还原及重金属沉淀。微生物群落的变化表明,重金属离子浓度的增加显著改变了反应器内微生物的群落结构,但该SRB菌群具有较好的重金属耐受性,脱硫生孢菌属(Desulfurispora)、脱硫弧菌属(Desulfovibrio)和脱硫弯曲孢菌属(Desulfosporosinus)在重金属离子浓度增加的条件下,丰度都有明显增加。SRB对SO_(4)^(2-)和重金属的还原效果为处理AMD废水提供了理论依据和方法借鉴。

SRB处理硫酸盐废水的影响因素探究

采用上流式固定床厌氧生物膜(UFAB)反应器处理人工模拟废水,研究了利用硫酸盐还原菌(SRB)处理硫酸盐废水的影响因素,考察了碳硫比、碳源种类、水力停留时间以及硫酸盐浓度等因素对硫酸盐去除效果的影响。结果表明:UFAB反应器在n(TOC)/n(SO_(4)^(2-))为6,甲酸-乙酸-乳酸钠混合碳源(三者物质的量比为1∶1∶4),进水硫酸盐质量浓度为1200 mg/L,水力停留时间为9 h的条件下,对硫酸盐平均去除率达83.80%,有较强的脱硫能力,出水硫酸盐平均质量浓度为194.4 mg/L,达到了GB 3838—2002《地表水环境质量标准》中作为集中式生活饮用水地表水源地的水质要求。

聚驱注采系统硫化物与SRB和SO_(4)^(2-)间相关性研究

对大庆油田某聚驱注采系统18处节点54个水样进行测试分析,研究不同节点水质参数和处理工艺对水中硫化物、硫酸盐还原菌(SRB)和SO_(4)^(2-)含量的影响规律,同时引入Copula函数明确硫化物含量与SRB及SO_(4)^(2-)含量间的相关性,进而建立含硫化物水样H_(2)S析出量预判图版。结果表明,硫化物和SRB整体含量增加,在油井处波动范围大,在沉降罐和过滤罐等密闭容器且水体停留时间较长的节点含量相对较高,在杀菌处含量大幅降低,在水井沿程含量呈逐渐增加趋势;SO_(4)^(2-)含量在地面系统沿程中总体呈下降趋势。Frank Copula函数可以有效描述硫化物含量与SRB及SO_(4)^(2-)含量之间的相关性,硫化物含量与SRB含量呈正相关,相关系数0.72;硫化物含量与SO_(4)^(2-)含量呈负相关,相关系数-0.28,说明硫化物含量主要与SRB含量相关。建立了基于水样温度、pH和SRB含量的H_(2)S析出量预测图版,预测误差在10%以内,预测效果良好。揭示了聚驱注采系统中硫化物的分布规律及H_(2)S析出风险情况,为油田水质处理过程中硫化物防治方法优化提供了参考。

不同Cl^(-)浓度下SRB对抗微生物腐蚀管材性能的影响

针对油田复杂环境下管材发生腐蚀失效问题,采用SEM、EDS及XRD对试样在不同Cl^(-)浓度下(0 g/L、20 g/L、40 g/L、80 g/L和120 g/L)腐蚀后的表面形貌、腐蚀产物的成分及物相组成进行分析,通过电化学测试,研究了不同Cl^(-)浓度下SRB对抗微生物腐蚀管材性能的影响。结果发现,Cl^(-)浓度为20 g/L时最适宜SRB生长,但此时SRB对抗微生物腐蚀管材的腐蚀性最小,此后随着Cl^(-)浓度升高,生物膜减少,腐蚀速率增大;当Cl^(-)浓度分别为0 g/L、20 g/L时,在腐蚀产物中检测出FeS和Fe_(3)(PO_(4))_(2),且腐蚀均受阴极反应控制。因此,在不同Cl^(-)浓度下,SRB对抗微生物腐蚀管材性能的影响与试样表面形成的生物膜有关,随着Cl^(-)浓度的增加,SRB对抗微生物腐蚀管材腐蚀作用减小。

Sample Generation for Security Region Boundary Identification Based on Topological Features of Historical Operation Data

Since the scale and uncertainty of the power sys-tem have been rapidly increasing,the computation efficiency of constructing the security region boundary(SRB)has become a prominent problem.Based on the topological features of histori-cal operation data,a sample generation method for SRB identi-fication is proposed to generate evenly distributed samples,which cover dominant security modes.The boundary sample pair(BSP)composed of a secure sample and an unsecure sam-ple is defined to describe the feature of SRB.The resolution,sampling,and span indices are designed to evaluate the cover-age degree of existing BSPs on the SRB and generate samples closer to the SRB.Based on the feature of flat distribution of BSPs over the SRB,the principal component analysis(PCA)is adopted to calculate the tangent vectors and normal vectors of SRB.Then,the sample distribution can be expanded along the tangent vector and corrected along the normal vector to cover different security modes.Finally,a sample set is randomly gen-erated based on the IEEE standard example and another new sample set is generated by the proposed method.The results in-dicate that the new sample set is closer to the SRB and covers different security modes with a small calculation time cost.

GLOBAL SOLUTIONS TO 1D COMPRESSIBLE NAVIER-STOKES/ALLEN-CAHN SYSTEM WITH DENSITY-DEPENDENT VISCOSITY AND FREE-BOUNDARY

This paper is concerned with the Navier-Stokes/Allen-Cahn system,which is used to model the dynamics of immiscible two-phase flows.We consider a 1D free boundary problem and assume that the viscosity coefficient depends on the density in the form ofη(ρ)=ρ^(α).The existence of unique global H^(2m)-solutions(m∈N)to the free boundary problem is proven for when 0<α<1/4.Furthermore,we obtain the global C^(∞)-solutions if the initial data is smooth.

Multi-scale physics-informed neural networks for solving high Reynolds number boundary layer flows based on matched asymptotic expansions

Multi-scale system remains a classical scientific problem in fluid dynamics,biology,etc.In the present study,a scheme of multi-scale Physics-informed neural networks is proposed to solve the boundary layer flow at high Reynolds numbers without any data.The flow is divided into several regions with different scales based on Prandtl's boundary theory.Different regions are solved with governing equations in different scales.The method of matched asymptotic expansions is used to make the flow field continuously.A flow on a semi infinite flat plate at a high Reynolds number is considered a multi-scale problem because the boundary layer scale is much smaller than the outer flow scale.The results are compared with the reference numerical solutions,which show that the msPINNs can solve the multi-scale problem of the boundary layer in high Reynolds number flows.This scheme can be developed for more multi-scale problems in the future.

Dirac method for nonlinear and non-homogenous boundary value problems of plates

The boundary value problem plays a crucial role in the analytical investigation of continuum dynamics. In this paper, an analytical method based on the Dirac operator to solve the nonlinear and non-homogeneous boundary value problem of rectangular plates is proposed. The key concept behind this method is to transform the nonlinear or non-homogeneous part on the boundary into a lateral force within the governing function by the Dirac operator, which linearizes and homogenizes the original boundary, allowing one to employ the modal superposition method for obtaining solutions to reconstructive governing equations. Once projected into the modal space, the harmonic balance method(HBM) is utilized to solve coupled ordinary differential equations(ODEs)of truncated systems with nonlinearity. To validate the convergence and accuracy of the proposed Dirac method, the results of typical examples, involving nonlinearly restricted boundaries, moment excitation, and displacement excitation, are compared with those of the differential quadrature element method(DQEM). The results demonstrate that when dealing with nonlinear boundaries, the Dirac method exhibits more excellent accuracy and convergence compared with the DQEM. However, when facing displacement excitation, there exist some discrepancies between the proposed approach and simulations;nevertheless, the proposed method still accurately predicts resonant frequencies while being uniquely capable of handling nonuniform displacement excitations. Overall, this methodology offers a convenient way for addressing nonlinear and non-homogenous plate boundaries.

Grain boundary engineering for enhancing intergranular damage resistance of ferritic/martensitic steel P92

Ferritic/martensitic(F/M)steel is widely used as a structural material in thermal and nuclear power plants.However,it is susceptible to intergranular damage,which is a critical issue,under service conditions.In this study,to improve the resistance to intergranular damage of F/M steel,a thermomechanical process(TMP)was employed to achieve a grain boundary engineering(GBE)microstructure in F/M steel P92.The TMP,including cold-rolling thickness reduction of 6%,9%,and 12%,followed by austenitization at 1323 K for 40 min and tempering at 1053 K for 45 min,was applied to the as-received(AR)P92 steel.The prior austenite grain(PAG)size,prior austenite grain boundary character distribution(GBCD),and connectivity of prior austenite grain boundaries(PAGBs)were investigated.Compared to the AR specimen,the PAG size did not change significantly.The fraction of coincident site lattice boundaries(CSLBs,3≤Σ≤29)and Σ3^(n) boundaries along PAGBs decreased with increasing reduction ratio because the recrystallization fraction increased with increasing reduction ratio.The PAGB connectivity of the 6%deformed specimen slightly deteriorated compared with that of the AR specimen.Moreover,potentiodynamic polarization studies revealed that the intergranular damage resistance of the studied steel could be improved by increasing the fraction of CSLBs along the PAGBs,indicating that the TMP,which involves low deformation,could enhance the intergranular damage resistance.

A High-Accuracy Curve Boundary Recognition Method Based on the Lattice Boltzmann Method and Immersed Moving Boundary Method

Applying numerical simulation technology to investigate fluid-solid interaction involving complex curved bound-aries is vital in aircraft design,ocean,and construction engineering.However,current methods such as Lattice Boltzmann(LBM)and the immersion boundary method based on solid ratio(IMB)have limitations in identifying custom curved boundaries.Meanwhile,IBM based on velocity correction(IBM-VC)suffers from inaccuracies and numerical instability.Therefore,this study introduces a high-accuracy curve boundary recognition method(IMB-CB),which identifies boundary nodes by moving the search box,and corrects the weighting function in LBM by calculating the solid ratio of the boundary nodes,achieving accurate recognition of custom curve boundaries.In addition,curve boundary image and dot methods are utilized to verify IMB-CB.The findings revealed that IMB-CB can accurately identify the boundary,showing an error of less than 1.8%with 500 lattices.Also,the flow in the custom curve boundary and aerodynamic characteristics of the NACA0012 airfoil are calculated and compared to IBM-VC.Results showed that IMB-CB yields lower lift and drag coefficient errors than IBM-VC,with a 1.45%drag coefficient error.In addition,the characteristic curve of IMB-CB is very stable,whereas that of IBM-VC is not.For the moving boundary problem,LBM-IMB-CB with discrete element method(DEM)is capable of accurately simulating the physical phenomena of multi-moving particle flow in complex curved pipelines.This research proposes a new curve boundary recognition method,which can significantly promote the stability and accuracy of fluid-solid interaction simulations and thus has huge applications in engineering.

Wavelet Multi-Resolution Interpolation Galerkin Method for Linear Singularly Perturbed Boundary Value Problems

In this study,a wavelet multi-resolution interpolation Galerkin method(WMIGM)is proposed to solve linear singularly perturbed boundary value problems.Unlike conventional wavelet schemes,the proposed algorithm can be readily extended to special node generation techniques,such as the Shishkin node.Such a wavelet method allows a high degree of local refinement of the nodal distribution to efficiently capture localized steep gradients.All the shape functions possess the Kronecker delta property,making the imposition of boundary conditions as easy as that in the finite element method.Four numerical examples are studied to demonstrate the validity and accuracy of the proposedwavelet method.The results showthat the use ofmodified Shishkin nodes can significantly reduce numerical oscillation near the boundary layer.Compared with many other methods,the proposed method possesses satisfactory accuracy and efficiency.The theoretical and numerical results demonstrate that the order of theε-uniform convergence of this wavelet method can reach 5.

Effect of Temperature and Grain Boundary on Void Evolution in Irradiated Copper:A Phase-Field Study

The continued existence of high-energy radiation in nuclear reactors at high temperatures results in the formation of radiation-induced voids,which will further lead to inevitable swellings of polycrystalline structural components and thus premature failures.A deep understanding of the effect of temperature and grain boundary on void evolution in irradiated copper is significant for preventing this kind of failures.Here,the phase-field method was employed to study void evolution in irradiated copper under different temperatures and grain sizes.The results show that,due to the different sensitivities of point defect production rate and vacancy diffusion rate to temperature changes,both the nucleation-growth rate and the coarsening rate during void evolution increase first and then decrease with increasing temperature;moreover,the nucleation mechanism exhibits site-saturated nucleation at low temperatures while continuous nucleation at high temperatures.The presence of grain boundary can accelerate the emergence of void because grain boundaries can absorb more interstitials than vacancies.The finer the grain size,the stronger inhibitory effect of grain boundaries on the growth rate of void,due to the formation of void denuded zone near grain boundaries.At high temperatures,the growth rate of void in fine grains is significantly reduced due to the increase of vacancy diffusion rate and the enhancement of sink effect of grain boundary on vacancy.

Experimental investigation on the permeability of gap-graded soil due to horizontal suffusion considering boundary effect

The boundary condition is a crucial factor affecting the permeability variation due to suffusion.An experimental investigation on the permeability of gap-graded soil due to horizontal suffusion considering the boundary effect is conducted,where the hydraulic head difference(DH)varies,and the boundary includes non-loss and soil-loss conditions.Soil samples are filled into seven soil storerooms connected in turn.After evaluation,the variation in content of fine sand(ΔR_(f))and the hydraulic conductivity of soils in each storeroom(C_(i))are analyzed.In the non-loss test,the soil sample filling area is divided into runoff,transited,and accumulated areas according to the negative or positive ΔR_(f) values.ΔR_(f) increases from negative to positive along the seepage path,and Ci decreases from runoff area to transited area and then rebounds in accumulated area.In the soil-loss test,all soil sample filling areas belong to the runoff area,where the gentle-loss,strengthened-loss,and alleviated-loss parts are further divided.ΔR_(f) decreases from the gentle-loss part to the strengthened-loss part and then rebounds in the alleviated-loss part,and C_(i) increases and then decreases along the seepage path.The relationship between ΔR_(f) and Ci is different with the boundary condition.Ci exponentially decreases with ΔR_(f) in the non-loss test and increases with ΔR_(f) generally in the soil-loss test.

Development of D_α band symmetrical visible optical diagnostic for boundary reconstruction on EAST tokamak

To investigate the potential of utilizing visible spectral imaging for controlling the plasma boundary shape during stable operation of plasma in future tokamak, a D_α band symmetric visible light diagnostic system was designed and implemented on the Experimental Advanced Superconducting Tokamak(EAST). This system leverages two symmetric optics for joint plasma imaging. The optical system exhibits a spatial resolution less than 2 mm at the poloidal cross-section, distortion within the field of view below 10%, and relative illumination of 91%.The high-quality images obtained enable clear observation of both the plasma boundary position and the characteristics of components within the vacuum vessel. Following system calibration and coordinate transformation, the image coordinate boundary features are mapped to the tokamak coordinate system. Utilizing this system, the plasma boundary was reconstructed, and the resulting representation showed alignment with the EFIT(Equilibrium Fitting) results. This underscores the system's superior performance in boundary reconstruction applications and provides a diagnostic foundation for boundary shape control based on visible spectral imaging.

CONVEXITY OF THE FREE BOUNDARY FOR AN AXISYMMETRIC INCOMPRESSIBLE IMPINGING JET

This paper is devoted to the study of the shape of the free boundary for a threedimensional axisymmetric incompressible impinging jet.To be more precise,we will show that the free boundary is convex to the fluid,provided that the uneven ground is concave to the fluid.

Two Stages Segmentation Algorithm of Breast Tumor in DCE-MRI Based on Multi-Scale Feature and Boundary Attention Mechanism

Nuclearmagnetic resonance imaging of breasts often presents complex backgrounds.Breast tumors exhibit varying sizes,uneven intensity,and indistinct boundaries.These characteristics can lead to challenges such as low accuracy and incorrect segmentation during tumor segmentation.Thus,we propose a two-stage breast tumor segmentation method leveraging multi-scale features and boundary attention mechanisms.Initially,the breast region of interest is extracted to isolate the breast area from surrounding tissues and organs.Subsequently,we devise a fusion network incorporatingmulti-scale features and boundary attentionmechanisms for breast tumor segmentation.We incorporate multi-scale parallel dilated convolution modules into the network,enhancing its capability to segment tumors of various sizes through multi-scale convolution and novel fusion techniques.Additionally,attention and boundary detection modules are included to augment the network’s capacity to locate tumors by capturing nonlocal dependencies in both spatial and channel domains.Furthermore,a hybrid loss function with boundary weight is employed to address sample class imbalance issues and enhance the network’s boundary maintenance capability through additional loss.Themethod was evaluated using breast data from 207 patients at RuijinHospital,resulting in a 6.64%increase in Dice similarity coefficient compared to the benchmarkU-Net.Experimental results demonstrate the superiority of the method over other segmentation techniques,with fewer model parameters.

Multi-soliton solutions of coupled Lakshmanan-Porsezian-Daniel equations with variable coefficients under nonzero boundary conditions

This paper aims to investigate the multi-soliton solutions of the coupled Lakshmanan–Porsezian–Daniel equations with variable coefficients under nonzero boundary conditions.These equations are utilized to model the phenomenon of nonlinear waves propagating simultaneously in non-uniform optical fibers.By analyzing the Lax pair and the Riemann–Hilbert problem,we aim to provide a comprehensive understanding of the dynamics and interactions of solitons of this system.Furthermore,we study the impacts of group velocity dispersion or the fourth-order dispersion on soliton behaviors.Through appropriate parameter selections,we observe various nonlinear phenomena,including the disappearance of solitons after interaction and their transformation into breather-like solitons,as well as the propagation of breathers with variable periodicity and interactions between solitons with variable periodicities.

Delineation of urban growth boundary based on FLUS model under the perspective of land use evaluation in hilly mountainous areas

With rapid economic development,the size of urban land in China is expanding dramatically.The Urban Growth Boundary(UGB)is an expandable spatial boundary for urban construction in a certain period in order to control the urban sprawl.Reasonable delineation of UGB can inhibit the disorderly spread of urban space and guide the normal development of the city.It is of practical significance for the construction of green urban space.The study utilizes GIS technology to establish a land construction suitability evaluation system for Nankang city,which is experiencing rapid urban expansion,and outlines the preliminary UGB under the future land use simulation(FLUS)model.At the same time,considering the coupled coordination of"Production-Living-Ecological Space",and based on the suitability evaluation,we revised the preliminary UGB by combining the advantages of the patch-generating land use simulation(PLUS)model and the convex hull model to delineate the final UGB.The results show that:1)the comprehensive score of the evaluation of the suitability of the construction of land from high to low shows the distribution of the center of the city to the surrounding circle type spread,the center of the city has the highest suitability score.The results of convex hull model show that the urban expansion type of Nankang is epitaxial.In the future,the urban expansion will mainly occur in the northern part of the city.The PLUS model predicts an increase of 3359.97 hm^(2)of construction land in Nankang by 2035,of which 2022.97 hm^(2)is urban construction land.2)The FLUS model has a prediction accuracy of 86.3%and delineates a preliminary UGB area of 9215.07 hm^(2).3)We used the results of the construction suitability evaluation,PLUS model simulation results,and convex hull model predictions to revise the originally delineated UGB.The final delineated UGB area is 8895.67 hm^(2)and it is capable of meeting the future development of the study area.The results of the delineation can promote sustainable urban development,and the delineation methodology can provide a reference basis for the preparation of territorial spatial planning.

Mask Boundary R-CNN实例分割边界精度算法

边界模糊问题在实例分割中是一个经典的难题,即使是在以高精度著称的双阶段实例分割中,边界处的分割效果也不理想,这是因为实例分割网络大多使用分类置信度作为依据进行掩膜的选择,它忽略了分割的边界信息,针对这个问题,本文提出了Mask Boundary R-CNN的实例分割框架,它包含两个评分预测分支,融合了更多图像边界的特征,重新学习并预测了掩膜的边界评分,并将两分支结果进行融合,得到的综合评分更能代表掩膜的边界质量,通过优先选择边界质量更好的掩膜来提高边界处的分割性能.在没有其他任何附加功能的情况下,Mask Boundary R-CNN在COCO2017数据集上分割精度比Mask R-CNN提升了约1.6%,尤其是在使用最新评价掩膜边界质量的指标APboundary衡量时,其边界分割精度比Mask R-CNN提升了约2%.

Analytical solutions of turbulent boundary layer beneath forward-leaning waves

As a typical nonlinear wave,forward-leaning waves can be frequently encountered in the near-shore areas,which can impact coastal sediment transport significantly.Hence,it is of significance to describe the characteristics of the boundary layer beneath forward-leaning waves accurately,especially for the turbulent boundary layer.In this work,the linearized turbulent boundary layer model with a linear turbulent viscosity coefficient is applied,and the novel expression of the near-bed orbital velocity that has been worked out by the authors for forward-leaning waves of arbitrary forward-leaning degrees is further used to specify the free stream boundary condition of the bottom boundary layer.Then,a variable transformation is found so as to make the equation of the turbulent boundary layer model be solved analytically through a modified Bessel function.Consequently,an explicit analytical solution of the turbulent boundary layer beneath forward-leaning waves is derived by means of variable separation and variable transformation.The analytical solutions of the velocity profile and bottom shear stress of the turbulent boundary layer beneath forward-leaning waves are verified by comparing the present analytical results with typical experimental data available in the previous literature.