排序方式: 共有34条查询结果,搜索用时 15 毫秒
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Markus Boese Tassilo Heeg Jürgen Schubert Martina Luysberg 《Journal of Materials Science》2006,41(14):4434-4439
Despite their potential application in strain-engineered layer structures, the epitaxial growth of rare earth scandate films on cubic perovskite substrates is not fully understood to date. Here we report on the epitaxy of the orthorhombic GdScO3 and DyScO3 on (001) BaTiO3 and SrTiO3 thin films. In particular, the orientation relationship between the orthorhombic epilayer and the cubic substrate is examined by aberration corrected high-resolution transmission electron microscopy. For all cases investigated, the long axis of the orthorhombic unit cell was found to be perpendicular to the growth direction. 相似文献
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Oleg Volkov Bartosz Protas Wenyuan Liao Donn W. Glander 《Journal of Engineering Mathematics》2009,65(3):201-220
A method is developed for optimizing the complex thermo-fluid phenomena that occur in welding processes where fluid convection is present. A mathematical model of a typical welding problem which includes conservation of mass, momentum and energy, and assumes that the process is steady in the frame of reference moving with the heat source is considered. An optimal control problem in which the heat input from the heat source is determined to ensure a prescribed geometry of the weld is formulated and solved. The problem is solved with a gradient-based optimization approach in which the gradient (sensitivity) of the cost functional with respect to the control variables is determined using a suitably defined adjoint system. An important aspect of the problem is that it is of the free-boundary type. Therefore it is necessary to use methods of the shape calculus to derive the adjoint equations. A number of computational results which validate our approach and feature qualitatively different flow patterns in problems with different material properties are presented. 相似文献
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Matthias Ahlhelm David Werner Johanna Maier Johannes Abel Thomas Behnisch Tassilo Moritz Alexander Michaelis Maik Gude 《Journal of the European Ceramic Society》2018,38(9):3369-3378
The so-called Freeze Foaming method aims at manufacturing ceramic cellular scaffolds for diverse applications. One application is dedicated to potential bone replacement material featuring open, micro and interconnected porosity. However, the main challenges of this foaming method is to achieve a homogeneous pore morphology. In a current project, the authors throw light on the bubble/pore and strut formation of this process by in situ computed tomography. This allows for evaluating varying process parameter’s effects on the growth of the ceramic foam during the foaming process. As first result and basis for CT analysis, a stable and reproducible model suspension was developed which resulted in reproducible foam structures. In dependence of selected process parameters like pressure reduction rate or air content in the ceramic suspension resulting Freeze Foams became adjustable with regard to their pore morphology. Pore size and distribution data as well as the porosity were characterized and evaluated accordingly. 相似文献
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This paper presents a two-phase control logic for anti-lock braking systems (ABS). ABS are by now a standard component in every modern car, preventing the wheels from going into a lock situation where the wheels are fixed by the brake and the stopping distances are greatly prolonged. There are different approaches to such control logics. An ABS design proposed in recent literature controls the wheel's slip by creating stable limit cycles in the corresponding phase space. This design is modified via an analytical approach that is derived from perturbation theory. Simulation results document shorter braking distance compared to available tests in the literature. 相似文献
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Ice-mould freeze casting of porous ceramic components 总被引:2,自引:0,他引:2
Porous, hollow ceramic components were produced by freeze casting technique. For this purpose aqueous slurries with high solid contents were prepared which were stable against freezing down to at least −5 °C. Ice cores were made by coating steel components with freezing water which were subsequently dip-coated with the ceramic suspensions. After freeze drying which removes both, the ice core and the frozen suspension liquid, and sintering, ceramic components with a high amount of open porosity including steel parts could be achieved. As an example hydroxyapatite was used for showing the opportunities of the freeze casting technology among others for applications in the field of bone replacement. The influence of the solid content of the hydroxyapatite slurries on the ice crystal growth has been investigated by means of compact hydroxyapatite bodies which were prepared by freeze casting using ice moulds with cylindrical cavities. 相似文献
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