Papers by Author: Qiang Wang

Abstract: Though the Support Vector Regression Machines (SVRM) is considered to be an effective method for time series prediction, its performance is greatly influenced by its parameters. In order to improve the rationality of parameter setting, the influences of the parameters (the number of support vectors N_S and the prediction length N_E) and signal characteristics on the SVRM performance were discussed. The results proved that the existence of confliction between prediction accuracy and prediction efficiency, and SVRM may inappropriate to long-term prediction, and N_S should be greater than a threshold which depends on the signal characteristics for an accurate prediction result. The research results may provide a theoretical basis for the improvments of SVRM algorithm.

Abstract: The microstructural changes of the primary Al3Ni phases in hypereutectic Al-Ni alloys solidified under various high magnetic field gradients were investigated. It was found that the application of a magnetic field gradient induced an aligned structure of the primary Al3Ni phases similar to those in a high uniform magnetic field. However, the high magnetic field gradient showed more obvious effect on the alignment of the primary Al3Ni phases than the uniform magnetic field, although this effect strongly depended on the alloy composition.

Abstract: Those materials with an one dimensional phase-aligned structure have a large amount of potentiality as engineering materials because of their exceptional optical, electrical and anisotropically mechanical properties. Many researchers are now working determinedly to explore the methods for fabricating this kind of material. Recently, high magnetic fields have been used to fabricate non-magnetic materials with textured structure where anisotropic magnetic energy should be strong enough to induce preferred crystal orientation. Based on this mechanism, we developed an in situ process for fabricating phase-aligned composites using high magnetic fields. In this work, hypoeutectic Mn-Sb and hypereutectic Al-Ni alloys were solidified in various magnetic fields. The primary MnSb dendrites in the solidified Mn-Sb alloys were found to be macrostructurally aligned along the field direction, while the primary Al3Ni phases in the Al-Ni alloys were found to be macrostructurally aligned perpendicular to the field direction. The X-ray diffraction (XRD) measurement results suggested that these two phases were also oriented by the magnetic field. It was believed that the above-mentioned alignment is based on the crystal orientation and relevant to the heat flux direction, the preferred growth direction and the concentration field around crystallized crystals.