Process optimization and related material properties of silicon films produced by laser-induced chemical vapour deposition from silane

Laser-induced chemical vapour deposition of silicon films on SiO₂/Si (1 0 0) and Si (1 0 0) substrates was studied using ArF laser irradiation of silane/argon gas mixture in parallel to the substrate. The optimal deposition conditions were specified by examination of film morphology at a wide range of irradiation and process parameters. At optimal conditions, specular films were obtained with no powder formation. The effect of deposition parameters, such as laser energy and repetition rate, on the deposition rate and the related film quality, was investigated.     

Preadhesion Laser Treatment of Aluminum Surfaces

An excimer laser may be used for preadhesion treatment of aluminum alloys. This method presents an alternative to the use of ecologically unfriendly chemicals involved in conventional anodizing pretreatments.

Experimental results indicate that preadhesion laser surface treatment significantly improved the shear strength of modified-epoxy bonded aluminum specimens compared with untreated and anodized substrates. The best results were obtained with laser energy of about 0.2 J/Pulse/cm² where single lap shear strength was improved by 600-700% compared with that of untreated Al alloy, and by 40% compared with chromic acid anodizing pretreatment.

The mode of failure changed from adhesive to cohesive as the number of laser pulses increased during treatment. The latter phenomenon has been correlated with morphology changes as revealed by electron microscopy, and chemical modification as indicated by Auger and infrared spectroscopy.

It can be concluded that the excimer laser has potential as a precise, clean and simple preadhesion treatment of Al alloys.     

Inconsistent heuristics in theory and practice

In the field of heuristic search it is usually assumed that admissible heuristics are consistent, implying that consistency is a desirable attribute. The term “inconsistent heuristic” has, at times, been portrayed negatively, as something to be avoided. Part of this is historical: early research discovered that inconsistency can lead to poor performance for A^? (nodes might be re-expanded many times). However, the issue has never been fully investigated, and was not re-considered after the invention of IDA^?.This paper shows that many of the preconceived notions about inconsistent heuristics are outdated. The worst-case exponential time of inconsistent heuristics is shown to only occur on contrived graphs with edge weights that are exponential in the size of the graph. Furthermore, the paper shows that rather than being something to be avoided, inconsistent heuristics often add a diversity of heuristic values into a search which can lead to a reduction in the number of node expansions. Inconsistent heuristics are easy to create, contrary to the common perception in the AI literature. To demonstrate this, a number of methods for achieving effective inconsistent heuristics are presented.Pathmax is a way of propagating inconsistent heuristic values in the search from parent to children. This technique is generalized into bidirectional pathmax (BPMX) which propagates values from a parent to a child node, and vice versa. BPMX can be integrated into IDA^? and A^?. When inconsistent heuristics are used with BPMX, experimental results show a large reduction in the search effort required by IDA^?. Positive results are also presented for A^? searches.     

Morphology of TiN coating produced by laser ablation

The morphology of TiN thin films on a steel surface produced by the process of laser ablation has been investigated. The process involves material removal from a titanium target by means of an ultraviolet excimer pulse laser. Both the target and the steel substrate are in an ammonia atmosphere and therefore the titanium atoms react with the nitrogen under the influence of a laser-induced plasma, and the product, which is TiN, is deposited on the surface of the steel. The investigation revealed that at the beginning of the process the TiN film is uniform; however, with increasing number of pulses, small micrometre-sized particles begin to appear on the surface and after a large number of pulses all the surface is covered with these particles.     

Effect of processing conditions on superconductive properties of laser-deposited YBCO thin films

Thin superconductive films of YBa₂Cu₃O_7−x have been deposited on (100) single crystal SrTiO₃ substrates by using technique of ArF pulse excimer laser evaporation of bulk YBCO target in a vacuum, followed by slow cooling in an oxygen atmosphere. Thin-film properties are strongly influenced by the processing conditions. The effect of pulse repetition rate, beam power, beam size on the target surface and oxygen pressure on the surface morphology and superconductive properties of deposited films has been investigated. Film characterization has been performed by using X-ray diffractometry, scanning electron microscopy and four-point probe electrical instruments.     

Celiac disease associated with systemic lupus erythematosus

Celiac disease in children has been occasionally reported to be associated with various disorders such as arthritis, cutaneous vasculitis and diabetes mellitus. We report on a 12-year-old girl with celiac disease, diagnosed at 1 year of age, who developed systemic lupus erythematosus. This association has not yet been reported in children.     

Fat-tree routing and node ordering providing contention free traffic for MPI global collectives

As the size of High Performance Computing clusters grows, so does the probability of interconnect hot spots that degrade the latency and effective bandwidth the network provides. This paper presents a solution to this scalability problem for real life constant bisectional-bandwidth fat-tree topologies. It is shown that maximal bandwidth and cut-through latency can be achieved for MPI global collective traffic. To form such a congestion-free configuration, MPI programs should utilize collective communication, MPI-node-order should be topology aware, and the packet routing should match the MPI communication patterns. First, we show that MPI collectives can be classified into unidirectional and bidirectional shifts. Using this property, we propose a scheme for congestion-free routing of the global collectives in fully and partially populated fat trees running a single job. The no-contention result is then obtained for multiple jobs running on the same fat-tree by applying some job size and placement restrictions. Simulation results of the proposed routing, MPI-node-order and communication patterns show no contention which provides a 40% throughput improvement over previously published results for all-to-all collectives.     

The fallacy of conventional signalling

All signals, with the exception of very special ones such as human verbal communication, evolve to be reliable. Communication systems that have been considered as systems of conventional signalling are reinterpreted as reliable systems by indicating the investment which increases their reliability. Examples are given from decorative patterns and set specific signals, such as status signals. The general importance of reliability is further discussed for cases such as the chemical signals within the multicellular organism, in which there is no conflict between the communicating parties. The reliability of signals which display symmetry, as is measured by the 'fluctuating asymmetry', is interpreted as a consequence of the investment required of signals that coordinate development.