Remote forcing of Indian Ocean warming on Northwest Pacific during El Nio decaying years:a FOAM model approach

This paper attempts to analyze in detail the remote influence of the Indian Ocean Basin warming on the Northwest Pacific （NWP） during the year of decaying E1 Nifio. Observation data and the Fast Ocean- Atmosphere coupled Model 1.5 were used to investigate the triggering conditions under which the remote influence is formed between the positive sea surface temperature （SST） anomaly in the North Indian Ocean and the Anomalous Northwest Pacific anticyclone （ANWPA）. Our research show that it is only when there is a contributory background wind field over the Indian Ocean, i,e., when the Indian Summer Monsoon （ISM） reaches its peak, that the warmer SST anomaly in the North Indian Ocean incites significant easterly wind anomalies in the lower atmosphere of the Indo-West tropical Pacific. This then produces the remote influence on the ANWPA. Therefore, the SST anomaly in the North Indian Ocean might interfere with the prediction of the East Asia Summer Monsoon in the year of decaying E1 Nifio. Both the sustaining effect of local negative SST anomalies in the NWP, and the remote effect of positive SST anomalies in the North Indian Ocean on the ANWPA, should be considered in further research.

DETERMINATION OF EFFECTIVE MODULI FOR FOAM PLASTICS BASED ON THREE PHASE SPHEROIDAL MODEL

The relations of bulk modulus, shear modulus, Young's modulus and the Poisson's ratio with porosity of foam plastics are determined by a three phase spheroidal model commonly used in Composite Mechanics. The results are compared with those using differential scheme. It is shown that the material properties derived from the present model normally are larger than those obtained by differential scheme for foam plastics with identical porosity. The differences in shear moduli and Young's moduli obtained by the two methods are small but they are larger for bulk moduli of incompressible matrix and Poisson's ratios. The Young's moduli of high density foam plastics derived by the present model agree better with experimental ones.

Mathematical models for foam-diverted acidizing and their applications

Foam diversion can effectively solve the problem of uneven distribution of acid in layers of different permeabilities during matrix acidizing. Based on gas trapping theory and the mass conservation equation, mathematical models were developed for foam-diverted acidizing, which can be achieved by a foam slug followed by acid injection or by continuous injection of foamed acid. The design method for foam-diverted acidizing was also given. The mathematical models were solved by a computer program. Computed results show that the total formation skin factor, wellhead pressure and bottomhole pressure increase with foam injection, but decrease with acid injection. Volume flow rate in a highpermeability layer decreases, while that in a low-permeability layer increases, thus diverting acid to the low-permeability layer from the high-permeability layer. Under the same formation conditions, for foamed acid treatment the operation was longer, and wellhead and bottomhole pressures are higher. Field application shows that foam slug can effectively block high permeability layers, and improve intake profile noticeably.

A three dimensional modeling method for spherical open cell aluminum foams based on spherical core stratification algorithm

Because of the complexity and irregularity of the internal structure of aluminum foam, it is difficult to establish a three-dimensional model that can accurately reflect this structure. In this study, an algorithm, named spherical core stratification algorithm, for three-dimensional modeling of spherical aluminum foam was proposed, and by using this algorithm, a three-dimensional model for sphere aluminum foam with random pores has been successfully constructed. The constructed model not only has a high similarity with the real structure of spherical open cell aluminum foam, but also can match its pore size and thickness by adjusting the size and number of holes in the random pore. In order to verify the feasibility of the modeling method, firstly, the three-dimensional model of the cylindrical spherical aluminum foam with a size of Φ35 mm × 20 mm and pore diameter of 5 mm has been generated by using the new algorithm. Secondly, taking the influence of relative density and shape function on the compressive properties of spherical open cell aluminum foams into consideration, a quasi-static constitutive model suitable for the material has been established based on the Sherwood-Frost classical compression constitutive model, which provides material parameters for quasi-static compression simulation. The comparison results show that the established constitutive equation has a good fit with the experiment, with a fitting correlation coefficient of above 0.99. Finally, the quasi-static compression simulation was carried out by ABAQUS, and the simulated nominal stress-strain curve was obtained. The simulation results indicate that the simulated stressstrain curve had the same trend with the one obtained by the quasi-static compression experiment with a small deviation.

Phase-Field Modeling for the Three-Dimensional Space-Filling Structure of Metal Foam Materials

Phase-field modeling for three-dimensional foam structures is presented. The foam structure, which is generally applicable for porous material design, is geometrically approximated with a space-filling structure, and hence, the analysis of the space-filling structure was performed using the phase field model. An additional term was introduced to the conventional multi-phase field model to satisfy the volume constraint condition. Then, the equations were numerically solved using the finite difference method, and simulations were carried out for several nuclei settings. First, the nuclei were set on complete lattice points for a bcc or fcc arrangement, with a truncated hexagonal structure, which is known as a Kelvin cell, or a rhombic dodecahedron being obtained, respectively. Then, an irregularity was introduced in the initial nuclei arrangement. The results revealed that the truncated hexagonal structure was stable against a slight irregularity, whereas the rhombic polyhedral was destroyed by the instability. Finally, the nuclei were placed randomly, and the relaxation process of a certain cell was traced with the result that every cell leads to a convex polyhedron shape.

ASP-FOAM提高高含水期油藏原油采收率效果的数值模拟研究

论述了ＡＳＰＦＯＡＭ提高原油采收率机理．建立了ＡＳＰＦＯＡＭ的基本数学模型和数值模型．对ＡＳＰＦＯＡＭ在岩心中驱替进行了数值模拟．实例计算表明：间注小段塞在现场是可行的．ＡＳＰＦＯＡＭ驱比水驱提高采收率２５％以上，比ＡＳＰ提高５％以上，比常规泡沫驱提高７％，以混合注入效果更好．

FOAM模拟的20世纪气候变化

在加入温室气体和太阳常数后,FOAM较好地模拟出20世纪气候变化的主要特征,与IPCC AR4模式和观测的结果基本保持一致,主要特征如下:(1)全球平均地表气温升高约0.6~0.7℃,海表面温度升高约0.4~0.5℃;地表温度升高不均匀,冰面大于陆地,陆地大于海洋,北半球大于南半球;对流层变暖,平流层变冷。(2)中纬度西风增强,西风带和信风带都有往极地移动的趋势,在南半球更明显;南北半球增暖的不对称可能影响信风的变化。(3)海表面温度经向梯度增大,和中纬度西风增强有互为因果的关系。(4)中低纬度蒸发加强,大气中的水汽增加,水汽的温室效应增强。(5)海洋上层增暖,副热带地区更明显;高纬度海洋变淡,太平洋变淡,印度洋和大西洋中低纬度变咸;北大西洋热盐环流减弱。

Modeling Research on a Solar Tower Thermal Collection-natural Gas Turbine Power System

塔式太阳能-燃气轮机发电系统发电成本和研发风险都低于常规太阳能热发电系统，同时能克服太阳能随机性、波动性的缺点，可以推动太阳能热发电的商业化进程。为了研究塔式太阳能与燃气轮机发电系统的能量传递与热功转化规律，以及相关结构参数与运行参数对发电系统性能的影响，该文分别建立该系统中压气机、泡沫陶瓷吸热器、燃烧室、透平4部分的传热和热功转化模型，采用Matlab软件平台编程，进行了系统运行仿真模拟，并分析了压比、孔隙率、厚度、吸热器面积、进气温度等对系统性能的影响。研究结果可为系统的设计与运行提供参考。

Effects of microstructure on uniaxial strength asymmetry of open-cell foams

Based on the elongated Kelvin model, the effect of microstructure on the uniaxial strength asymmetry of open-cell foams is investigated. The results indicate that this asymmetry depends on the relative density, the solid material, the cell morphology, and the strut geometry of open-cell foams. Even though the solid material has the same tensile and compressive strength, the tensile and compressive strength of open-cell foams with asymmetrical sectional struts are still different. In addition, with the increasing degree of anisotropy, the uniaxial strength as well as the strength asymmetry increases in the rise direction but reduces in the transverse direction. Moreover, the plastic collapse ratio between two directions is verified to depend mainly on the cell morphology. The predicted results are compared with Gibson and Ashby＇s theoretical results as well as the experimental data reported in the literature, which validates that the elongated Kelvin model is accurate in explaining the strength asymmetry presented in realistic open-cell foams.

Analysis and simulation for tensile behavior of anisotropic open-cell elastic foams

Based on the elongated Kelvin obtained to investigate the tensile behavior Kelvin model＇s periodicity and symmetry in model, a simplified periodic structural cell is of anisotropic open-cell elastic foams due to the whole space. The half-strut element and elastic deflection theory are used to analyze the tensile response as done in the previous studies. This study produces theoretical expressions for the tensile stress-strain curve in the rise and transverse directions. In addition, the theoretical results are examined with finite element simulation using an existing formula. The results indicate that the theoretical analysis agrees with the finite element simulation when the strain is not too high, and the present model is better. At the same time, the anisotropy ratio has a significant effect on the mechanical properties of foams. As the anisotropy ratio increases, the tensile stress is improved in the rising direction but drops in the transverse direction under the same strain.

Elasto-plastic analysis of crack in metallic foams

To determine the solutions of the well-known problem of a finite width strip with single edge crack,some results on elasto-plastic fracture analysis for metallic foams are reported.Meanwhile,in order to discuss and put an insight into the nonlinear fracture analysis,the Dugdale model for plastic deformation of this configuration for metallic foams is recommended and solved.Combining the asymptotic solution with the Dugdale model and elastic solution,the stress field in the plastic zone and the size of the plastic zone are expressed as analytical forms.Based on Williams expansion method,the estimate of the scale factor is also completed and analyzed.In view of these analytical solutions,the results show the scale factor is a useful parameter for the fracture theory of metallic foams.

聚氨酯泡沫注浆修复材料泡孔结构特征及抗压性能研究进展

聚氨酯泡沫(PUF)注浆修复材料以轻质高强、快凝高膨胀等优势,在基础设施修复加固领域得到了广泛的应用。抗压性能是工程修复材料十分重要的力学指标之一,而材料的微观结构对其宏观力学行为有决定性影响。近年来,国内外专家学者对PUF注浆修复材料的微观结构特性和抗压性能进行了大量研究,但尚未见到系统性总结。本文介绍了PUF注浆修复材料的定义及反应过程,综述了其微观泡孔结构特性、压缩应力-应变关系和本构模型,从宏微观角度讨论了其变形和破坏机理,总结了密度、试件尺寸、应变率和特殊环境工况对压缩性能的影响机理及规律,最后展望了PUF注浆修复材料未来的研究方向。

STOCHASTIC ELASTO-PLASTIC FRACTURE ANALYSIS OF ALUMINUM FOAMS

Model I quasi-static nonlinear fracture of aluminum foams is analyzed by considering the effect of microscopic heterogeneity. Firstly, a continuum constitutive model is adopted to account for the plastic compressibility of the metallic foams. The yield strain modeled by a two- parameter Weibull-type function is adopted in the constitutive model. Then, a modified cohesive zone model is established to characterize the fracture behavior of aluminum foams with a cohesive zone ahead of the initial crack. The tensile traction versus local crack opening displacement relation is employed to describe the softening characteristics of the material. And a Weibull statistical model for peak bridging stress within the fracture process zone is used for considering microscopic heterogeneity of aluminum foams. Lastly, the influence of stochastic parameters on the curve of stress-strain is given. Numerical examples are given to illustrate the numerical model presented in this paper and the effects of Weibull parameters and material properties on J-integral are discussed.

Exact Solution of a Cylinder Tube Made of Metallic Foam Under Inner Pressure

Exact solution of the stress and velocity fields of a cylinder tube of metallic foams under inner pressure is given in which the Triantafillou and Gibson constitutive law （TG model） for the material is taken as a basis of the calculation. The nonlinear equation is turned linear equation by introducing a kinematics parameter. The differences between the full condensed materials and the effect of the relative density are also discussed.

Polymer Foam Flow in Porous Media under Different Injection Modes

The mathematical models of the flow of polymer foam in porous media under three injection modes are established and the relevant numerical calculation methods are given. The profiles of the liquid phase saturation, the pressure drop and the number density of the flowing HPAM foam in artificial sandstone cores with the dimensionless distance under three injection modes are numerically calculated and analyzed. The results show that, compared with the injection mode 2 and 3, HPAM foam flows in a piston-like fashion in the artificial sandstone core under the injection mode 1 and produces the biggest pressure drop. Obviously, the flood efficiency is the highest under the injection mode 1.

The effects of relative density of metal foams on the stresses and deformation of beam under bending

The exact analytic solution of the pure bending beam of metallic foams is given. The effects of relative density of the material on stresses and deformation are revealed with the Triantafillou and Gibson constitutive law （TG model） taken as the analysis basis. Several examples for individual foams are discussed, showing the importance of compressibility of the cellular materials. One of the objects of this study is to generalize Hill＇s solution for incompressible plasticity to the case of compressible plasticity, and a kinematics parameter is brought into the analysis so that the velocity field can be determined.

Mathematical modeling for dynamic stability of sandwich beam with variable mechanical properties of core

The paper is devoted to mathematical modelling of static and dynamic stability of a simply supported three-layered beam with a metal foam core. Mechanical properties of the core vary along the vertical direction. The field of displacements is for- mulated using the classical broken line hypothesis and the proposed nonlinear hypothesis that generalizes the classical one. Using both hypotheses, the strains are determined as well as the stresses of each layer. The kinetic energy, the elastic strain energy, and the work of load are also determined. The system of equations of motion is derived using Hamilton＇s principle. Finally, the system of three equations is reduced to one equation of motion, in particular, the Mathieu equation. The Bubnov-Galerkin method is used to solve the system of equations of motion, and the Runge-Kutta method is used to solve the second-order differential equation. Numerical calculations are done for the chosen family of beams. The critical loads, unstable regions, angular frequencies of the beam, and the static and dynamic equilibrium paths are calculated analytically and verified numerically. The results of this study are presented in the forms of figures and tables.

MODULUS PREDICTION AND DISCUSSION OF REINFORCED SYNTACTIC FOAMS WITH COATED HOLLOW SPHERICAL INCLUSIONS

The elastic properties of syntactic foams with coated hollow spherical inclusions have been studied by means of Mori and Tanaka's concept of average stress in the matrix and Eshelby's equivalent inclusion theories.Some formulae to predict the effective modulus of this material have been derived theoretically.Based on these formulae,the influences of coating parameters such as the thickness and (Poisson's) ratio on the modulus of the syntactic foams have been discussed at the same time.

Laboratory Validation of an Integrated Surface Water— Groundwater Model

The hydrodynamic surface water model DIVAST has been extended to include horizontally adjacent groundwater flows. This extended model is known as DIVAST-SG (Depth Integrated Velocities and Solute Transport with Surface Water and Groundwater). After development and analytical verification the model was tested against a novel laboratory set-up using open cell foam (60 pores per inch—ppi) as an idealised porous media representing a riverbank. The Hyder Hydraulics Laboratory at Cardiff University has a large tidal basin that was adapted to simulate a surface water—groundwater scenario using this foam, and used to validate the DIVAST-SG model. The properties of the laboratory set-up were measured and values were determined for hydraulic conductivity (permeability) and porosity, evaluated as 0.002 m/s and 75% respectively. Lessons learnt in this initial experimentation were used to modify the flume construction and improve the experimental procedure, with further experimentation being undertaken of both water level variations and tracer movement. Valuable data have been obtained from the laboratory experiments, allowing the validity of the numerical model to be assessed. Modifications to the input file to include representations of the joints between the foam blocks allowed a good fit between the observed and modelled water levels. Encouraging correlation was observed in tracer experiments using Rhodamine-WT dye between the observed exit points of the tracer from the foam, and the modelled exit points with time.

基于改进的SuperGlue模型的浮选泡沫稳定度检测方法研究

在浮选过程中,浮选泡沫保持一定的稳定度对保证浮选指标的稳定至关重要。由于浮选泡沫本身的复杂性和现有检测方法的局限性,目前还无法对工业现场泡沫的稳定度进行定量检测和评估。为此,开发了一种基于改进的SuperGlue模型的浮选泡沫图像特征匹配算法,用于对浮选泡沫的稳定度进行测量。该算法采用改进的SuperPoint模型网络对泡沫图像进行特征点提取,将原有的VGG网络进行了改进,利用特征匹配模型对所得到的两组特征点进行匹配,再进行误匹配精筛选,设置置信度阈值进一步提升匹配精度。对比了在匹配算法中应用比较多的GMS算法,本文算法的有效特征点匹配对数提升了19.58%,匹配精度达99.85%。与传统灰度差值法对比,本文的泡沫稳定度测量方法对不同状态的泡沫可辨识性提升明显,极大地提高了图像检测灵敏度,可以满足生产对泡沫稳定度测量的要求。