Advanced Materials Research Vols. 308-310

Abstract: In this paper, a novel super large metal organic chemical vapor deposition (MOCVD) reactor with three inlets located on the periphery of reactor was proposed and numerical evaluation of growth conditions for GaN thin film was characterized. In this design, the converging effects of gas flow in the radial direction could counterbalance the dissipation of metal organics source. CFD was used for the mathematical solution of the fluid flow, temperature and concentration fields. A 2-D model utilizing axisymmetric mode to simulate the gas flow in a MOCVD has been developed. The growth of GaN films using TMGa as a precursor, hydrogen as carrier gas was investigated. The effects of flow rates, mass fraction of various species, operating pressure, and gravity were analyzed and discussed, respectively. The numerical simulation results show all the fields distributions were in an acceptable range.

Abstract: As the wide application of retroreflective materials, following problems such as safety warning effect, quality, manufacturing technology, test method become more and more important. Many national test centers or big manufactures build retroreflection measurement systems. In order to identify these laboratories’ ability, we organize this laboratory comparison. After 6 months experiments, this comparison successfully finishes. And all the test data are dealt with statistical analysis.

Abstract: This paper proposes a meshless Galerkin level set method for structural shape and topology optimization of continua. To taking advantage of the implicit free boundary representation scheme, structural design boundary is represented through the introduction of a scalar level set function as its zero level set, to flexibly handle complex shape fidelity and topology changes by maintaining concise and smooth interface. Compactly supported radial basis functions (CSRBFs) are used to parameterize the level set function and also to construct the shape functions for mesh free function approximation. The meshless Galerkin global weak formulation is employed to implement the discretization of the state equations. This provides a pathway to simplify two numerical procedures involved in most conventional level set methods in propagating the discrete level set functions and in approximating the discrete equations, by unifying the two different stages at two sets of grids just in terms of one set of scattered nodes. The proposed level set method has the capability of describing the implicit moving boundaries without remeshing for discontinuities. The motion of the free boundary is just a question of advancing the discrete level set function by finding the design variables of the size optimization in time. One benchmark example is used to demonstrate the effectiveness of the proposed method. The numerical results showcase that this method has the ability to simplify numerical procedures and to avoid numerical difficulties happened in most conventional level set methods. It is straightforward to apply the present method to more advanced shape and topology optimization problems.

Abstract: Roughness parameters such as the root-mean-square (RMS) roughness in super smooth surfaces are heavily influenced by evaluation ways and measuring method. With the help of CCI6000, relationships were investigated respectively between the RMS roughness with the instrument parameter set and cutoff wavelength. The study revealed that there was an optimal set of measurement parameters and a dynamic cutoff wavelength that would identify different wavelength regimes when measuring super smooth surfaces. It was found that the proposed scheme greatly reduced the influences of CCI instrument parameters and cutoff length on RMS roughness in the measurement of hard disk surfaces. RMS roughness exhibited a steady-state trend and the processed surface morphology conformed to the arrangement of atoms and the polishing feature of CMP technique.

Abstract: Such evaluation standards as plumpness, roundness, force of cold upsetting, and the volume are made through the research on cold upsetting steel ball. Through a designed orthogonal test and the DEFORM simulation analysis, the process of ball billet is explained reasonably after primary selection and screening. Thus through comparison, it is seen that the original process is improved to a large degree.

Abstract: Accord to the research on microcosmic mechanism of steel ball grinding, analyze the law of abrasive’s movement on the surface of steel ball, and then establish the elimination process and grinding effect by the analyzes software such as CATIA, establish a general model about how to remove the excess material on steel ball surface, and find the relationship between the influencing factors. With the help of the research above, we can provide a foundation of detailed study and improvement about various processes of grinding ball.

Abstract: in order to improve the efficiency and accuracy of steel ball processing, analyze the main influential factors, to propose the new technology and equipments of damping plate system and obtain the new solutions of the efficiency and accuracy of steel ball processing.

Abstract: According to the characteristics of the shape of sounding board, the structure is immersed in gunpowder pulsation flow, the virtual mass method can be used to research on sounding board. The 3-dimensional element is used to discretize the sounding board and its surrounding air, the gas is coupled with the structure directly by the gas mass matrix. The coupling motion equation model of the sounding board and its surrounding air can be derived.The coupling modal of the sounding board system is calculated by using the software of ansys, and the data of gunpowder explosion pressure pulsation is obtained from the calculation in autodyn, then the frequency and modal of the sounding board system were further analyzed in the software of ansys. The results show that there are some significant changes in the frequency and modal of the sounding board system under the condition of prestress as well as the air-structure coupling of gunpowder pulsation fluid flow.

Abstract: Anodic dissolution on p-type silicon thin film in hydrofluoric acid solutions leads to a reduction of roughness on these surfaces. The electrochemical behavior in different HF concentration is investigated by linear sweep scan, and it is found that the HF has an important role in electrochemical behaviors, and the anodic dissolution rate increases with increasing HF concentration. A smooth surface state can be obtained in HF solutions, and the technique is promising for fabrication of reflecting silicon surfaces.

Abstract: A new improved multidiscipline feasible (MDF) strategy based on the updating approximate function constructed by Response Surface Method (RSM) is firstly pointed out and denoted as MDF-update-RSM which involves double cycles. Before the start of inner loop on MDF-update-RSM strategy, the approximate function is initialized by RSM on a set of sampling points which are generated from the Design of Experiment (DOE). With the process of outer loop, the coefficients and one high-order term of polynomial are updated and upgrade by the Least Square Regression. The ability of this new strategy promotes the efficiency and saves huge calculational cost incurred by the MDF strategy which always runs on the multidisciplinary analysis (MDA). The MDF-update-RSM is good procedure to ameliorate the accuracy that has been tested by the Rosenbrock function in this paper. Finally, the optimization strategy is employed on executing the low pressure turbine shrouded blade design and provides a true optimal result compared to the classical MDF strategy.