A Descriptive Model of Robot Team and the Dynamic Evolution of Robot Team Cooperation

At present, the research on robot team cooperation is still in qualitative analysis phase and lacks the description model that can quantitatively describe the dynamical evolution of team cooperative relationships with constantly changeable task demand in Multi-robot field. First this paper whole and static describes organization model HWROM of robot team, then uses Markov course and Bayesian theorem for reference, dynamical describes the team cooperative relationships building. Finally from cooperative entity layer, ability layer and relative layer we research team formation and cooperative mechanism, and discuss how to optimize relative action sets during the evolution. The dynamic evolution model of robot team and cooperative relationships between robot teams proposed and described in this paper can not only generalize the robot team as a whole, but also depict the dynamic evolving process quantitatively. Users can also make the prediction of the cooperative relationship and the action of the robot team encountering new demands based on this model. Journal web page & a lot of robotic related papers www.ars-journal.co

Compliant copper microwire arrays for reliable interconnections between large low-CTE packages and printed wiring board

The trend to high I/O density, performance and miniaturization at low cost is driving the industry towards shrinking interposer design rules, requiring a new set of packaging technologies. Low-CTE packages from silicon, glass and low-CTE organic substrates enable high interconnection density, high reliability and integration of system components. However, the large CTE mismatch between the package and the board presents reliability challenges for the board-level interconnections. Novel stress-relief structures that can meet reliability requirements along with electrical performance while meeting the cost constraints are needed to address these challenges. This thesis focuses on a comprehensive methodology starting with modeling, design, fabrication and characterization to validate such stress-relief structures. This study specifically explores SMT-compatible stress-relief microwire arrays in thin polymer carriers as a unique and low-cost solution for reliable board-level interconnections between large low-CTE packages and printed wiring boards. The microwire arrays are pre-fabricated in ultra-thin carriers using low-cost manufacturing processes such as laser vias and copper electroplating, which are then assembled in between the interposer and printed wiring board (PWB) as stress-relief interlayers. The microwire array results in dramatic reduction in solder stresses and strains, even with larger interposer sizes (20 mm × 20 mm), at finer pitch (400 microns), without the need for underfill. The parallel wire arrays result in low resistance and inductance, and therefore do not degrade the electrical performance. The scalability of the structures and the unique processes, from micro to nanowires, provides extendibility to finer pitch and larger package sizes. Finite element method (FEM) was used to study the reliability of the interconnections to provide guidelines for the test vehicle design. The models were built in 2.5D geometries to study the reliability of 400 µm-pitch interconnections with a 100 µm thick, 20 mm × 20 mm silicon package that was SMT-assembled onto an organic printed wiring board. The performance of the microwire array interconnection is compared to that of ball grid array (BGA) interconnections, in warpage, equivalent plastic strain and projected fatigue life. A unique set of materials and processes was used to demonstrate the low-cost fabrication of microwire arrays. Copper microwires with 12 µm diameter and 50 µm height were fabricated on both sides of a 50 µm thick, thermoplastic polymer carrier using dryfilm based photolithography and bottom-up electrolytic plating. The copper microwire interconnections were assembled between silicon interposer and FR-4 PWB through SMT-compatible process. Thermal mechanical reliability of the interconnections was characterized by thermal cycling test from -40°C to 125°C. The initial fatigue failure in the interconnections was identified at 700 cycles in the solder on the silicon package side, which is consistent with the modeling results. This study therefore demonstrated a highly-reliable and SMT-compatible solution for board-level interconnections between large low-CTE packages and printed wiring board.Ph.D

Molecular cloning, expression profiling, and yeast complementation of 19 β-tubulin cDNAs from developing cotton ovules

Microtubules are a major structural component of the cytoskeleton and participate in cell division, intracellular transport, and cell morphogenesis. In the present study, 795 cotton tubulin expressed sequence tags were analysed and 19 β-tubulin genes (TUB) cloned from a cotton cDNA library. Among the group, 12 cotton TUBs (GhTUBs) are reported for the first time here. Transcription profiling revealed that nine GhTUBs were highly expressed in elongating fibre cells as compared with fuzzless-lintless mutant ovules. Treating cultured wild-type cotton ovules with exogenous phytohormones showed that individual genes can be induced by different agents. Gibberellin induced expression of GhTUB1 and GhTUB3, ethylene induced expression of GhTUB5, GhTUB9, and GhTUB12, brassinosteroids induced expression of GhTUB1, GhTUB3, GhTUB9, and GhTUB12, and lignoceric acid induced expression of GhTUB1, GhTUB3, and GhTUB12. When GhTUBs were transformed into the Saccharomyces cerevisiae inviable mutant, tub2, which is deficient in β-tubulin, one ovule-specific and eight of nine fibre-preferential GhTUBs rescued this lethality. This study suggests that the proteins encoded by cotton GhTUBs are involved during cotton fibre development