The interaction between molten gallium and the hydrocarbon medium induced by ultrasonic energy—can gallium carbide be formed?

Ultrasonic irradiation of molten gallium in organic liquids (decane, dodecane, etc.) results in dispersion of the gallium into nanometric spheres. These were examined by several analytical methods XRD, DSC, Raman and IR spectroscopy) as well as electron microscopy (SEM, TEM) and found to be composed of Ga and C. The DSC analysis indicates that the Ga has possibly reacted with carbon, while the Raman spectrum of the product demonstrates a strong additional peak that could not be identified. This work explores the possibility that the product is gallium carbide or another gallium‐carbon complex. To investigate the nature of the product, we performed detailed extended X‐ray absorption fine structure (EXAFS) and X‐ray absorption near‐edge structure (XANES) analyses. On the basis of DSC, IR, and Raman it appear to be formation of GaC, whereas the analysis by EXAFS and XANES demonstrated that the gallium is found to be in a higher reduced state (almost metallic), supported by carbon. The question that remains open in addition to the one related to the formation of galium carbide is whether a complex structure, including oxygen contamination is involved in the layers surrounding the Ga as indicated by the EXAFS results.     

Fast set intersection and two-patterns matching

In this paper we present a new problem, the fast set intersection problem, which is to preprocess a collection of sets in order to efficiently report the intersection of any two sets in the collection. In addition we suggest new solutions for the two-dimensional substring indexing problem and the document listing problem for two patterns by reduction to the fast set intersection problem.     

Three-jet electrospinning using a flat spinneret

Electrospinning is a simple but highly versatile technology to produce nanofibers from solutions or melts mostly of polymers using electrostatic forces. A primary challenge facing electrospinning is its low productivity mainly limited by flow rate. In this work, a custom-made three-hole spinneret instead of conventional needles was adopted to enhance the flow rate of electrospinning. Three-jet formation, nanofiber deposition, nanofiber morphology and size were characterized by digital camera and scanning electron microscopy (SEM) as the effects of several governing parameters in electrospinning, including applied voltage from 19.8 to 21.0 kV, working distance from 15.2 to 16.8 cm and flow rate from 6.0 to 9.0 mL/h. It was found that three simultaneous stable jets were ejected from the three-hole spinneret under suitable operating conditions. Moreover, it was found that the fibers collected from the jets from each hole deposited separately in circular spots on a stationary collector. The resultant fibers mostly have an average diameter of less than 300 nm. It has been proved that simple holes on a flat surface can be used to electrospin nanofibers. The three-hole spinneret produces nanofibers at flow rates greater than that in single needle electrospinning. Flow rate has the potential to be easily scaled up by increasing the spinneret diameter and the number of holes.     

Fairness in context-free grammars under every choice-strategy

In (Porat et al., 1982, Inform. and Control 55, 108–116) the notion of fair derivations in context-free grammars was introduced and studied. The main result there is a characterization of fairly terminating grammars as non-variable-doubling. In this paper we show that the same characterization is valid under canonical derivations in which the next variable to be expanded is deterministically chosen, leaving nondeterminism only to the decision as to which rule (of the chosen variable) to apply. Two families of canonical derivations are introduced and studied as special cases: spinal derivations and layered derivations.     

The electronic spreadsheet as a didactic learning enhancement

A variety of quantitative techniques (such as capital budgeting or linear programming) may be understood more fully by students when they are able to work through relatively simple applications of the techniques by hand. Unfortunately, such manual computations are inherently susceptible to arithmetic errors. The authors propose that students use the electronic spreadsheet to work out these types of problems during their initial learning stage. An advantage of the electronic spreadsheet for this purpose is the automatic calculation of data by the program thereby eliminating the usual arithmetic errors. As long as appropriate formulas are correctly entered into the spreadsheet, the results should be correct.The method presented by the authors does not yield general solutions to capital budgeting or to linear programming problems. Rather, the methodology requires the student to think through the solution process while removing some of the usual drudgery and potential inaccuracies of manual solutions.     

Learning Automata from Ordered Examples

Connectionist learning models have had considerable empirical success, but it is hard to characterize exactly what they learn. The learning of finite-state languages (FSL) from example strings is a domain which has been extensively studied and might provide an opportunity to help understand connectionist learning. A major problem is that traditional FSL learning assumes the storage of all examples and thus violates connectionist principles. This paper presents a provably correct algorithm for inferring any minimum-state deterministic finite-state automata (FSA) from a complete ordered sample using limited total storage and without storing example strings. The algorithm is an iterative strategy that uses at each stage a current encoding of the data considered so far, and one single sample string. One of the crucial advantages of our algorithm is that the total amount of space used in the course of learning for encoding any finite prefix of the sample is polynomial in the size of the inferred minimum state deterministic FSA. The algorithm is also relatively efficient in time and has been implemented. More importantly, there is a connectionist version of the algorithm that preserves these properties. The connectionist version requires much more structure than the usual models and has been implemented using the Rochester Connectionist Simulator. We also show that no machine with finite working storage can iteratively identify the FSL from arbitrary presentations.