Applied Mechanics and Materials Vol. 620

Abstract: Pin structure GaN-based alpha particle detector with epitaxial growth on c-plane sapphire substrate through metal organic chemical vapor deposition (MOCVD) method, uses electron beam evaporation and photoetching machine to produce the ohmic contact electrodes of device. The electrical properties of device which were tested by I-V and C-V show that the device’s reverse leakage current is 9.9μA at 100V reverse bias voltage is at; and the detector’s junction capacitance is 19pF at 20V reverse bias voltage.

Abstract: Thermo-physical properties of magnetic fluid were measured experimentally at various temperatures, in order to evaluate their temperature dependencies. Heat transfer by natural convection was also investigated in a horizontal enclosed rectangular container filled with the tested magnetic fluid. It was found that the heat transfer coefficient of the magnetic fluid keeps good agreement with the conventional heat-transfer correlation of natural convection heat transfer in a horizontal enclosed rectangular container by applying the values of thermo-physical properties obtained in the present work. Therefore, the measured thermo-physical properties are reliable and can be used as a thermo-physical database of the magnetic fluid.

Abstract: Thermo-physical properties of three kinds of phase change materials (sodium acetate trihydrate, erythritol and sodium sulfate decahydrate) were measured experimentally at various temperatures, in order to evaluate those temperature dependencies. Heat transfer by natural convection was also investigated in a horizontal enclosed rectangular container filled with the tested phase change materials, which was heated at the lower surface and cooled at the upper surface. It was found that the heat transfer coefficient of the liquid phase keeps good agreement with the conventional heat-transfer correlation of natural convection heat transfer in a horizontal enclosed rectangular container by applying the values of thermo-physical properties obtained in the present work.

Abstract: With the use of Magnetic Abrasive Finishing (MAF) to polish surfaces of the parts, roughness on the surfaces can reach a level like a mirror. We have devoted to the study of MAF for many years; the magnetic abrasive particle we have developed can yield a value of Ra 0.008μm (R_max0.1μm), which is similar to the surface of a mirror. However, there is no way to absorb charging of abrasive particle during polishing for conventional stiff abrasive materials. Therefore, it is difficult to obtain the nanolevel mirror surface. The study is based on silicon rubber and mix Sic and pure iron powder to develop elastic magnetic abrasive particles. During the process, employing the micro elastic of the polymer elastic magnetic abrasive particle to make the particle shape change and increase the contact area, therefore to improve the surface roughness by micro polishing to achieve a nanolevel mirror polishing demand。 The particle could be made easily in a short time, therefore it could reduce production cost and achieve environmental protection simultaneously.

Abstract: Abstract: Thickness of oil film, a parameter of an oil-air lubrication system, is an important evaluation criterion for two-phase annular flow flowed in the system. Experiment of the effects of oil volume-per-cycle on oil film’s thickness is done on a special test rig using ECT technology, and then the changing rule of oil film’s thickness is analyzed in this paper. The results show that, at the first the thickness of oil film is thinness and weakness, and then it changes to thickness and stabilization, at the last the oil focusing on the bottom of tube. The break of annular flow and the blocking of oil at elbow tube have been studied experimentally and theoretically.