Papers by Author: J. Hu

Abstract: Few existing systems can support the reuse of conceptual design knowledge due to the lack of satisfying modeling technologies. In the present study, we investigated the ontology-based modeling technologies and apply them to develop a framework of conceptual design knowledge management. The practicability and validity of our framework were then examined in a Construction Machinery Design Knowledge Management System.

Abstract: Many thin-walled structure components widely used in aero industries not only have complex structure and large size, but also need high machining accuracy. However, because of their poor rigidity, it is easy to bring machining deformation caused by the existence of the initial residual stresses, the fixing stresses, cutting forces and cutting heat. The difficulty in ensuring their machining accuracy becomes a big problem, so that how to effectively predict and control the machining deformation has become an important subject in the development and production of our national defense weapons. This paper established a 3-D Finite element model with consideration of milling forces, clamping forces and initial residual stress field. By using this model, machining deformation of thin-walled frame shape workpieces has been computed. The simulated results are compared with experimental data, and the correctness of the simulation is verified. The study is helpful to the prediction and the control of machining deformation for thin-walled parts.

Abstract: Mechanical properties of DNA, for example the elastic modulus, are of vital importance for its biological function. Previously, the modulus is mainly obtained by bending, stretching and twisting DNA using various techniques and tools. By applying vibrating mode scanning polarization force microscopy (VPSFM), deformations of DNA under ultra-small indentation forces can be measured and so the radial modulus can be computed. In this paper, modeling of the VPSFM measuring system is presented. The system is modeled as a spring-mass-damper oscillator under various force fields, such as van der Waals force, attractive electrical force and repulsive interactions between the tip and sample. The electrical polarization force is described by using uniformly charged line model and the DNA is considered to be a simple elastic rod. By numerically integrating the equation of tip motion, the contact force and the radial modulus of DNA under different deformation can be calculated. We found that in measuring radial modulus of DNA, the existence of substrate cannot be neglected, especially when the relative large deformation is reached.

Abstract: With area detector X-ray diffraction system, the orientation of superconductor films and their relationships with substrates can be easily examined. For YBCO high temperature superconductor films having complex crystalline orientation relationship fore and after melting process, 2-dimesional X-ray diffraction provides us much more information than common X-ray diffraction. This is very helpful for understanding the peritectic reaction during melting process because the growth mechanism of Y211 crystalline can be explained from its orientation information. Y211 phrase in the film and its orientation relationship with YBCO phase and MgO substrate have been analyzed at first. It is found that Y211 crystalline is well match with both MgO substrate and YBCO parent phase. Then the melting process of YBCO has been discussed from the view of the orientation relationship between each phase.