A simple incompressible flux splitting for sharp free surface capturing

This paper first applies a flux vector‐type splitting method based on the numerical speed of sound for computing incompressible single and multifluid flows. Here, a preconditioning matrix based on Chorin's artificial compressibility concept is used to modify the incompressible multifluid Navier–Stokes equations to be hyperbolic and density or volume fraction‐independent. The current approach can reduce eigenvalues disparity induced from density or volume fraction ratios and enhance numerical stability. Also, a simple convection‐pressure flux‐splitting method with high‐order essentially nonoscillatory‐type primitive variable extrapolations coupled with monotone upstream‐centered schemes for conservation laws‐type volume fraction recompressed reconstruction is used to maintain the preservation of sharp interface evolutions in multifluid flow simulations. Benchmark tests including a solid rotation test of a notched two‐dimensional cylinder, the evolution of spiral and rotational shapes of deformable circles, a dam breaking problem, and the Rayleigh–Taylor instability were chosen to validate the current incompressible multifluid methodology. An incompressible driven cavity was also chosen to check the robustness of the proposed method on the computation of single fluid incompressible flow problems. Copyright © 2011 John Wiley & Sons, Ltd.     

Crack problems of piezoelectric materials

This paper presents an analysis of crack problems in homogeneous piezoelectrics or on the interfaces between two dissimilar piezoelectric materials based on the continuity of normal electric displacement and electric potential across the crack faces. The explicit analytic solutions are obtained for a single crack in piezoelectrics or on the interfaces of piezoelectric bimaterials. A class of boundary problems involving many cracks is also solved. For homogeneous materials it is found that the normal electric displacementD ₂ induced by the crack is constant along the crack faces which depends only on the applied remote stress field. Within the crack slit, the electric fields induced by the crack are also constant and not affected by the applied electric field. For the bimaterials with realH, the normal electric displacementD ₂ is constant along the crack faces and electric fieldE ₂ has the singularity ahead of the crack tip and a jump across the interface. The project is supported by the National Natural Science Foundation of China(No. 19704100) and the Natural Science Foundation of Chinese Academy of Sciences(No. KJ951-1-201).     

含噁嗪环硅烷偶联剂对石英纤维/含硅芳炔复合材料性能的影响

从石英纤维(QF)、含硅芳炔树脂(PSA)分子结构特点出发,设计并合成了一种含有噁嗪环和端炔的新型硅烷偶联剂(BCA),并以BCA改善QF/PSA复合材料的界面性能。采用差示扫描量热分析(DSC)、红外光谱分析(FT-IR)、X-射线电子能谱(XPS)及扫描电镜(SEM)等测试手段表征了BCA与QF/PSA复合材料的相互作用和界面改性效果。结果表明:BCA能够分别与PSA和QF形成良好的化学键合,改善复合材料的界面黏结;经w=2.0%的BCA处理后,QF/PSA复合材料的层间剪切强度、弯曲强度分别较未处理前提高了69.1%和68.8%。     

Numerical simulation of incompressible two‐phase flows with a Boussinesq–Scriven interface stress tensor

We consider the numerical simulation of a three‐dimensional two‐phase incompressible flow with a viscous interface. The simulation is based on a sharp interface Navier–Stokes model and the Boussinesq–Scriven constitutive law for the interface viscous stress tensor. In the recent paper [Soft Matter 7, 7797–7804, 2011], a model problem with a spherical droplet in a Stokes Poiseuille flow with a Boussinesq–Scriven law for the surface viscosity has been analyzed. In that paper, relations for the droplet migration velocity are derived. We relate the results obtained with our numerical solver for the two‐phase Navier–Stokes model to these theoretical relations. Copyright © 2013 John Wiley & Sons, Ltd.     

GC models for separation optimization in pressure‐tunable tandem capillary columns operated isothermally

In the previous part of this study, a significant improvement of the fundamental relationships that control GC resolution in a pressure‐tunable assembly operating in isothermal conditions inside a single oven was made. A theoretical approach for the correct choice of the working temperature was proposed for the first time. In this second part of our report, a new interfacing device has been proposed for a rapid and reliable alignment of the two columns at the midpoint junction. Moreover, the results of a series of experimental tests have confirmed the validity of the proposed mathematical models.     

Influence of the interface material layers and semiconductor energetic disorder on the open circuit voltage in polymer solar cells

Material layers at electrode/semiconductor interfaces are fundamental for the photovoltaic properties of polymer solar cells. The relationship between open‐circuit voltage ( V_OC ) and the work function ( φ ) of these interface layers is still a matter of debate. Simulations, together with experiments on over more than 20 cell architectures based on P3HT:PC₆₀BM, enabled us to analyze the physical dependence of V_OC on φ . In particular, when the work function of the contacts is well inside the gap we observe that performance depends strongly on even small variations of φ . On the other hand, when it approaches the energy levels of the semiconducting polymers, device operation becomes the most efficient and less sensitive to variations in φ . Furthermore, by varying the Gaussian density of states (DOS) of the active blend we were able to show that V_OC performance depends significantly also on the DOS. Our study based on the simultaneous variation of transport layers represents a promising method to optimize the design and performance of polymer solar cells. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 690–699     

Analysis of a cracked concrete containing an inclusion with inhomogeneously imperfect interface

The distributed dislocation technique is applied to determine the behavior of a cracked concrete matrix containing an inclusion. The analysis of cracked concrete in the presence of inclusions such as steel expansions is a practical problem that needs special attention. The solution to the problem of interaction of an edge dislocation with a circular inclusion having circumferentially inhomogeneously imperfect interface is available in the literature. This analytical solution is used in the distributed dislocation technique to obtain the stress intensity factor for the cracked concrete in the presence of inclusion. The interface of the matrix and the inclusion is assumed inhomogeneously imperfect and the stress intensity factor is determined for the cracked concrete for a case of two identical cracks on diametrically opposite sides of the inclusion. Consideration of this general inhomogeneously imperfect interface is the contribution of this paper. The variation of the inhomogeneity parameters is studied and presented. Additionally, the general assumption for the interface is simplified to the special case of perfectly bonded interface. The observations for the perfect interface are coincident with the previously reported results.     

Effect of different types of substrate surface treatments on the graphene device performance

Graphene–substrate interface is very crucial for analyzing graphene device performance. In this article, we have shown how the graphene device performance got affected because of different types of substrate surface treatment techniques used before graphene transfer. For fabrication of graphene devices, monolayer chemical vapor deposition (CVD) graphene was transferred onto SiO₂ grown thermally on Si substrate. Forming gas annealed SiO₂/Si shows better device performance as compared with as-grown SiO₂ on Si substrate. A further effect of oxygen plasma and argon plasma cleaning of SiO₂ surface before graphene transfer was investigated. Forming gas annealing improves the performance and plasma treatment degrade the graphene devices' performance.     

“离子迁移”实验的改进及其实验条件优化*

针对“离子迁移”实验中实验现象不明显、实验操作难度大的问题。采用将CuSO₄、K₂CrO₄与淀粉加工成热的糊状流体,趁热装入U型管,冷却后变成半固体的方法,解决了上述问题。并采用单因素实验法对淀粉的用量、CuSO₄与K₂CrO₄混合物的用量(CuSO₄与K₂CrO₄物质的量之比为1∶1)以及迁移电压等实验条件进行优化。优化后的实验结果显示,离子迁移后形成的区域颜色与半固体淀粉的颜色差别很大,便于学生远距离识别。该方法操作简单、现象明显,有利于一线教师的教学演示和学生的分组实验。     

解读生命健康及抗击新冠疫情中的表界面物理化学知识*

以表界面物理化学的视角看待和解读抗疫科研成果,充分挖掘生命健康,讨论新冠疫情事件中的病毒检测和传播、护目镜起雾及口罩防护涉及到的知识点,结合物理化学6个章节中的热力学第一和第二定律、胶体化学、表面化学、相平衡和溶液等内容来理解。抽象概念和理论与现实抗疫元素的有机结合,使学生能够学以致用。