Pulsed Current MICRO Plasma Arc Welding (PCMPAW) is one of the most widely used welding processes in sheet metal manufacturing industry. In any fusion arc welding process, the weld BEAD geometry plays an important role in determining the mechanical properties of the weld, which helps to improve the weld quality. Moreover, the geometry of weld BEAD involves several simultaneous quality characteristics, such as front width, back width, front height and back height, which must closely be monitored, controlled and optimized. This paper presents the optimization of the PCMPAW process by using the grey relational analysis considering the aforementioned quality characteristics, which are of maximum front width and back width, also minimum front height and back height.In relation to this, experiments were performed under different welding conditions such as peak current, back current, pulse rate and pulse width using AISI 304L stainless steel sheets of 0.25mm thickness using Response Surface Method (RSM) based on Central Composite Design (CCD) experimental design. It was observed that optimal welding parameters were determined by the grey relational grade from the grey relational analysis and they were also verified through confirmation experiments.

Suspension polymerization processes are significantly important in polymer BEAD formation. One of the important factors for BEAD size control in these processes is variation in surface tension. In this research, the prediction of optimum concentration of a surface active agent was investigated on the basis of the experimental surface tension diagrams. The experimental data show that the desired surface tension for a specific size distribution of expandable polystyrene BEADs is 64.5 mN/m. In spite of non-linear dependence of surface tension on concentration, the expandable polystyrene BEAD size distribution histograms indicate that the predicted concentration of sodium alkylbenzenesulfonate by the experimental model match its found optimum value.

Using the transfer-matrix method, Spin transport in ferromagnetic bilayer graphene superlattice, which can be realized by putting a series of ferromagnetic insulator layers on top of a bilayer grapheme is studied. The ferromagnetic layers with exchange energy Eex are in contact with gate of potential energy V0. It is considered that the magnetization in the two ferromagnetic layers are aligned parallel (P) and antiparallel (AP) to each other. The spin transmissions probability (T­ and T¯) and the spin conductance (G­ and G¯) are studied. The spin polarization is calculated through the spin conductance. The total conductance (Gpq and GAPq) is also considered. It is found that perfect reflection can occur at normal incident, i.e., T­=T= 0. The spin conductance and the swpin polarization are found to exhibit oscillatory depending on the barrier height. The highest value of oscillating amplitude for SP% can rich 100% or (-100%) under special condition.

An irreversible Stirling heat pump cycle using ferromagnetic materials as a cyclic working substance is established. The influences of finite-rate heat transfer, heat leak, regeneration time, regenerative loss and the internal irreversibility on the cyclic performance of magnetic heat pumps are taken into account. On the basis of the thermodynamic properties of ferromagnetic materials, the performance characteristic of the ferromagnetic Stirling heat pump cycle is investigated. Also, by applying the optimization technology, the relation between the optimal heating load and the coefficient of performance (COP) is derived. Furthermore, the maximum heating load and the corresponding COP as well as the maximum COP and the corresponding heating load are determined and discussed in detail. The results obtained in the present paper may provide some new information for the optimal design and the development of real magnetic heat pumps.