Controlling the ON-resistance in SOI LDMOS using parasitic bipolar junction transistor

We present a new parasitic bipolar junction transistor (BJT) enhanced silicon on insulator (SOI) laterally double diffused metal oxide semiconductor (LDMOS), called BJT enhanced LDMOS (BE-LDMOS). The proposed device utilizes the parasitic BJT present in an LDMOS to increase the drain current for a given gate voltage, resulting in a reduction in the ON-resistance by 26.2 % and improving the switching speed by 7.8 % for BE-LDMOS as compared to the comparable LDMOS. These improvements are without degradation in other performance parameters such as off state breakdown voltage and transconductance. The process steps for fabricating BE-LDMOS are same as that for LDMOS except for an additional metal contact.     

A heuristic approach for U-shaped assembly line balancing to improve labor productivity

The assembly line balancing problem is a non deterministic polynomial type planning problem for mass production. Layout design changes constitute a major decision that yields investment for assembly operations and numerous heuristics have been reported in the literature for solving the line balancing problems. U-shaped assembly layout offers several benefits over traditional straight-line layout in implementation of lean manufacturing and Just-In-Time technology. In the paper an attempt has been made to evaluate labor productivity in U-shaped line system and straight line system. A Critical Path Method (CPM) based approach for U-shaped assembly line has been applied for assigning the task to the work stations for assembly line layout. Results show that the CPM based U-shaped approach performs better and improve the labor productivity of assembly line layout.     

Defect engineering of graphene for effective hydrogen storage

Although several modifications to graphene have been proposed to improve its hydrogen binding to practical levels, current theoretical studies largely neglect the role of topological defects. In this paper we analyze the effect of these defects and their possible use in a hydrogen storage system. Hydrogen physisorption on five types of point defects (Stone-Wales, single vacancy and three types of double vacancy) was investigated using density functional theory with the PBE-GGA functional. Point defects were also repeated with the vdW-DF2 functional to better represent long range van der Waals interactions. Although none of the defects were found to be detrimental to hydrogen anchoring, only the single vacancy showed promising hydrogen binding in the ideal range. Model systems combining different defects were also explored, including a defect-anchored metal system, a bilayer graphene system and a grain-boundary system. Finally, two high defect density structures constructed using vacancies and combined Stone-Wales defects and vacancies yielded gravimetric densities of 5.81% and 7.02%, respectively, with the vdW functional. This study suggests that graphene can be defect-engineered to develop effective hydrogen storage media.     

A Fuzzy AHP and PROMETHEE method-based heuristic for disassembly line balancing problems

Nowadays, new products have been introduced in the market at an ever increasing pace due to rapid technology advancement. Consequently, products are becoming outdated and discarded faster than ever before. Since the demand for new solutions to economically deal with such outdated products begun to rise, the disassembly line has emerged as a viable solution to this problem. The disassembly line has been considered as a viable choice for automated disassembly of returned products. The problem of sequence generation in disassembly is complex due to its NP-Hard nature and therefore the heuristically solutions are most preferable for these types of problems. In this paper, a heuristic has been proposed to assign the disassembly tasks/parts to the work stations under its precedence constraints. It incorporates Fuzzy analytic hierarchy process (Fuzzy AHP) and PROMETHEE method for the selection of tasks for assignment to the disassembly line. The Fuzzy AHP has been used to find the relative importance of each criteria and PROMETHEE method has been used for prioritising the tasks for assignment. The proposed heuristics has been illustrated with an example and the results have been compared to the heuristic proposed by McGovern and Gupta. The proposed heuristic performs well and has shown improvements in terms of cycle time and idle time of the workstations.     

Bulk Ultrafine-Grained Interstitial-Free Steel Processed by Equal-Channel Angular Pressing Followed by Flash Annealing

Interstitial-free steel workpieces are deformed by equal-channel angular pressing (ECAP) for equivalent strain ε_vm = 3 and ε_vm = 21 followed by flash annealing. Microstructures are analyzed by optical microscopy, scanning electron microscopy and transmission electron microscopy. Mechanical properties are evaluated by hardness testing. Yield strength of materials is calculated from hardness values. Flash annealing (at 675 °C) of ECAPed samples for ε_vm = 3 and ε_vm = 21 results in abnormal subgrain growth and abnormal grain growth, respectively. Flash annealing at 700 °C of ECAPed (at ε_vm = 3) IF steel converts abnormally grown subgrains to grains which serve as nuclei for recrystallization and that result in bimodal grain size distribution. Bimodal grain size distribution is also produced when ECAPed IF steel for ε_vm = 21 is flash annealed at 675 °C due to abnormal grain growth or secondary recrystallization. Flash annealing of IF steel samples ECAPed for low ε_vm, in the temperature range 600-675 °C, decreases the hardness continuously with increase in the annealing temperature but it increases at high ε_vm. The former is due to annihilation of defects but the later is caused by ordering of nonequilibrium boundaries. The hardening and strengthening behaviors are similar.