Shift-or string matching with super-alphabets

Given a text T[1…n] and a pattern P[1…m] over some alphabet Σ of size σ, we want to find all the (exact) occurrences of P in T. The well-known shift-or algorithm solves this problem in time O(n⌈m/w⌉), where w is the number of bits in machine word, using bit-parallelism. We show how to extend the bit-parallelism in another direction, using super-alphabets. This gives a speed-up by a factor s, where s is the number of characters processed simultaneously. The algorithm is implemented, and we show that it works well in practice too. The result is the fastest known algorithm for exact string matching for short patterns and small alphabets.     

Modelling opinion formation driven communities in social networks

In a previous paper we proposed a model to study the dynamics of opinion formation in human societies by a co-evolution process involving two distinct time scales of fast transaction and slower network evolution dynamics. In the transaction dynamics we take into account short range interactions as discussions between individuals and long range interactions to describe the attitude to the overall mood of society. The latter is handled by a uniformly distributed parameter α, assigned randomly to each individual, as quenched personal bias. The network evolution dynamics is realised by rewiring the societal network due to state variable changes as a result of transaction dynamics. The main consequence of this complex dynamics is that communities emerge in the social network for a range of values in the ratio between time scales. In this paper we focus our attention on the attitude parameter α and its influence on the conformation of opinion and the size of the resulting communities. We present numerical studies and extract interesting features of the model that can be interpreted in terms of social behaviour.     

Microstructure and Porosity of Laser Welds in Cast Ti-6Al-4V with Addition of Boron

Metallurgical and Materials Transactions A - Addition of small amounts of boron to cast Ti-6Al-4V alloy has shown to render a finer microstructure and improved mechanical properties. For such an...     

Metallocene‐based functionalized polyolefins as compatibilizers in polyolefin nanocomposites

This article reports a study of some functionalized polyolefins evaluated as compatibilizers in polyethylene nanocomposites. The functionalized polymers were prepared by direct metallocene‐mediated copolymerizations of ethylene and a functional comonomer. The prepared nanocomposites were evaluated for mechanical and barrier property enhancement. A good combination of mechanical and barrier properties was obtained with the metallocene‐based functionalized polyethylene. The toughness–stiffness balance was better than or comparable to that achieved with conventional functionalized polymers such as maleic anhydride grafted polyethylene. The results also indicated that these metallocene‐based functionalized polyolefins, when used as compatibilizers, could have relatively higher molar masses and lower functionality than those of conventional post‐reactor‐modified compatibilizers, and so the drawbacks associated with the latter could be avoided. Their inherent properties could also further improve the final nanocomposite properties. This was attributed to the more homogeneous nature of metallocene‐catalyzed polymers in comparison with post‐reactor‐modified products. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1094–1100, 2004     

A COMPARISON OF HPLC WITH FLUORESCENCE DETECTION AND FIXED WAVELENGTH FLUORESCENCE METHODS FOR THE DETERMINATION OF POLYCYCLIC AROMATIC HYDROCARBON METABOLITES IN FISH BILE

Fish exposed to polycyclic aromatic hydrocarbons (PAHs) accumulate only a small amount of PAH in their tissues. Hydrophobic PAHs are readily transformed into hydrophilic metabolites and excreted in bile. Bile samples of five fish species were collected from the Baltic Sea and analyzed using two methods: high-performance liquid chromatography (HPLC) with fluorescence detection and a fixed wavelength fluorescence method. With the HPLC method PAH compounds were quantitated after hydrolysis, and with the fluorescence method without enzyme-assisted hydrolysis. In HPLC analysis the major metabolite in all fish species, 1-hydroxypyrene, was the only metabolite detected in perch and salmon samples. 1-Hydroxyphenanthrene was detected in a few flounder and in most eelpouts. The correlation between the two methods for pyrene-type metabolites was good (r² = 0.773).     

Influence of High-Temperature Heat Treatment on Barrier and Functional Properties of Polyolefin-Coated Papers

In this study, the effect of heat treatment on barrier and functionality of polyolefin-coated papers was investigated. The aim was to find the optimal improvements on barrier without losing the applicability of the materials due to physical damages. The results of the study proved considerable improvement in barrier characteristics of the structures. Both water vapor and oxygen transmission rates of LDPE-coatings decreased linearly following the set-temperature until 200°C. At this point, the treatment caused a continuing decrease in oxygen transmission achieving 10 × lower transmission levels than the untreated structure, whereas moisture transport faced corresponding but lower increase. This was considered to be caused by the difference in diameter of the H₂O and O₂ molecules; the smaller water molecules are able to penetrate between spherulites, whose size increased due to higher treatment temperature followed by cooling.     

Adhesion of extrusion‐coated polymer sealing layers to a fiber‐based packaging material with an atomic layer deposited aluminum oxide surface coating

Adhesion of extrusion‐coated polymer sealing layers on an atomic layer deposited (ALD) aluminum oxide (Al₂O₃) surface coating was investigated with a view to gain information on the applicability of ALD deposited barrier layers in fiber‐based packaging materials. The polymers used for the sealing layer were low density polyethylene (LDPE), polyethylene terephthalate (PET), and polylactide (PLA). They were extrusion‐coated onto the ceramic side of paper/PET/Al₂O₃ substrates, where the Al₂O₃ layer was a few tens of nanometers thick. According to the results, good adhesion was obtained for LDPE coating, whereas the other coatings showed a considerable lack of adhesion. Presumably, the oxidation faced by LDPE in the air gap of the extrusion‐coating process was able to create an extensive number of reactive sites that strongly bonded with the hydroxyl groups on the oxide surface of the substrate. With the PET and PLA coatings, such oxidation did not occur and the adhesion obtained remained at a relatively poor level. With all of the coatings, the adhesion levels were improved using corona discharge equipment as a pretreatment prior to the extrusion‐coating process. POLYM. ENG. SCI., 52:1985–1990, 2012. © 2012 Society of Plastics Engineers     

Effects of measurement errors in predictor selection of linear regression model

Measurement errors may affect the predictor selection of the linear regression model. These effects are studied using a measurement framework, where the variances of the measurement errors can be estimated without setting too restrictive assumptions about the measurement model. In this approach, the problem of measurement is solved in a reduced true score space, where the latent true score is multidimensional, but its dimension is smaller than the number of the measurable variables. Various measurement scales are then created to be used as predictors in the regression model. The stability of the predictor selection as well as the estimated predicted validity and the reliability of the prediction scales is examined by Monte Carlo simulations. Varying the magnitude of the measurement error variance four sets of predictors are compared: all variables, a stepwise selection, factor sums, and factor scores. The results indicate that the factor scores offer a stable method for predictor selection, whereas the other alternatives tend to give biased results leading more or less to capitalizing on chance.     

Improved Soft-Output RAKE Receiver for CDMA Mobile Terminals with High Data Rates

In this paper we propose a soft-output RAKE receiver for CDMA mobile terminals using low spreading factor and/or high-order modulation constellations for high data rates. Based on the outputs of theRAKE correlator fingers, the receiver produces symbol or bit metrics for soft decision decoding. The formulation of these metrics is derived analytically taking into account the multipath propagation, interfering users and channel estimation errors. Simulations show thata performance gain is achieved when low spreading factors or high-order modulation constellations are used.