Tae-Sik Lee

In this investigation, a new approach based on the energy minimization method is proposed to analyze the mechanism of the metal transfer (globular and spray modes) in the GMAW process. Energies due to the surface tension, gravity, electromagnetic and drag forces exerted on the pendant drop are minimized and the shape of molten drop in the equilibrium state is calculated without presumed geometry. The energy due to the electromagnetic force is derived using the Maxwell stress. Effects of welding

The precise geometry of the molten drop attached to the electrode has substantial influence on the metal transfer. The geometry of the drop is a function of various parameters including the welding current and voltage, composition of shielding gas, electrode extension and material properties of the electrode. A new approach is proposed to enable an improved description of the molten drop drop in equilibrium. Among various forces which influence the profile of the static pendant drop, the surface

Numerous research efforts have evidenced that the solder joint profile in SMT affects reliability of the joint. In this work, the three-dimensional solder joint profile of the J-lead is predicted by minimizing the energy due to surface tension and gravity. Geometric complexity stemming from the curved shape of the J-lead is resolved by employing a transformed coordinate and corresponding element types with the geometric continuity condition in the finite element formulation. Based on the simulat

ZnBeO and ZnCdSeO alloys have been disclosed as materials for the improvement in performance, function, and capability of semiconductor devices. The alloys can be used alone or in combination to form active photonic layers that can emit over a range of wavelength values. Materials with both larger and smaller band gaps would allow for the fabrication of semiconductor heterostructures that have increased function in the ultraviolet (UV) region of the spectrum. ZnO is a wide band-gap material poss

FastSLAM is a widely-used framework for simultaneous localization and mapping using a Rao-Blackwellized particle filter. However, FastSLAM degenerates over time due to the particle depletion in resampling phase, mainly caused by the loss of particle diversity. In this work, a dispersion technique for recovering the particle diversity is proposed to improve the performance of FastSLAM. First, when particle diversity is lost after resampling phase, a source which helps particles be dispersed is ge