A communication–computation efficient group key algorithm for large and dynamic groups

The management of secure communication among groups of participants requires a set of secure and efficient operations. In this paper we extend existing work to present a Communication–Computation Efficient Group Key Algorithm (CCEGK) designed to provide both efficient communication and computation, addressing performance, security and authentication issues of CCEGK. Additionally, we compare CCEGK with three other leading group key algorithms, EGK, TGDH, and STR. An analytical comparison of all algorithms revealed eight similar methods: add, remove, merge, split, mass add, mass remove, initialize, and key refresh. Comparing the cost in terms of communication and computation, we found CCEGK to be more efficient across the board.     

Transformation of carbon nanotubes to diamond in microwave hydrogen plasma

Multiwall carbon nanotubes (MWCNTs), synthesized by microwave plasma enhanced chemical vapor deposition, were used as the precursor to synthesize diamond in a pure hydrogen microwave discharge. Diamond-scratched silicon wafers, with and without precoated MWCNTs, were placed side by side on a substrate holder. Diamond was formed on both wafers with the consumption of MWCNTs. The present results suggest that the solid–gas–solid transformation mechanism is involved in this process.     

An effect of side chain length on the solution structure of poly(9,9-dialkylfluorene)s in toluene

The effect of side chain length of π-conjugated poly(9,9-dialkylfluorene)s has been studied in semi-dilute (10 mg/mL) toluene solutions using small-angle neutron scattering (SANS) and ¹H and ²H NMR spectroscopies. Under these conditions, SANS data indicate that poly(9,9-dinonylfluorene) and poly(9,9-dioctylfluorene) are dissolved down to the molecule level and appear as elongated one-dimensional chains (length >20-30 nm). In contrast, the shorter side chain polymers exhibit a self-association so that poly(9,9-diheptylfluorene) forms thin sheet-like (∼1 nm) and poly(9,9-dihexylfluorene) thin (∼1 nm) and thick sheet-like (>6 nm) aggregates. ¹H NMR data, together with the density functional theory (DFT) calculations, however, show that this occurs without changes in the conformation of the polymer backbone.     

Concomitant Crystallization of Copper(II) Sachharinato Complexes with 2-methylpyrazine as a Monomer and an One-dimensional Polymer: Syntheses,Crystal Structures,Spectroscopic and Thermal Properties

The reaction of [Cu(sac)₂(H₂O)₄] · 2H₂O with 2-methylpyrazine (mpyz) leads two complexes, concomitant crystallization of a mononuclear complex [Cu(sac)₂(mpyz)(H₂O)₂] (1) and a polymeric complex [Cu(sac)₂(μ-mpyz)]_n (2). Both complexes have been characterized by elemental analyses, magnetic measurements, FT-IR and ESR, TG-DTA and single-crystal X-ray diffraction analyses. Single-crystal X-ray analyses show that complex 1 consists of discrete molecules in which the copper(II) ions exhibits a square-pyramidal coordination geometry. The individual molecules of 1 are connected into a hydrogen-bonded chain structure, which is further assembled to form a three-dimensional network by π–π stacking interactions. Complex 2 is an 1D coordination polymer in which copper(II) centers are bridged by the mpyz ligand. The chains are further assembled to form two-dimensional frameworks by π–π and C–H···π stacking interactions.     

Comparative study of self-assembling of multilayers using reactive sputter deposition and mass selective ion beam deposition

While experimenting with the growth of metal-containing amorphous carbon (a-c:Me) thin films using two different growth processes, self-assembled multilayered structures were observed. One of the processes is a reactive magnetron sputter deposition process. The other process is a mass selective ion beam deposition process. Despite of the differences in the growth method and the growth condition, self-assembled multilayered thin films, consisting of alternating dark layer and bright layer, were obtained in both processes. Based on the consideration of energy for atomic diffusion in the thin films, the growth mechanism is discussed.     

Forecasting total natural-gas consumption in Spain by using the stochastic Gompertz innovation diffusion model

The principal objective of the present study is to examine the possibilities of using a Gompertz-type innovation diffusion process as a stochastic growth model of natural-gas consumption in Spain, and to compare our results with those obtained, on the one hand, by stochastic logistic innovation modelling and, on the other, by using a stochastic lognormal growth model based on a non-innovation diffusion process. Such a comparison is carried out taking into account the macroeconomic characteristics and natural-gas consumption patterns in Spain, both of which reflect the current expansive situation characterizing the Spanish economy. From the technical standpoint a contribution is also made to the theory of the stochastic Gompertz Innovation diffusion process (SGIDP), as applied to the case in question.     

Thermoelastic evaluation of composite laminates using digital imaging processing

The study of the variation of the curvature of non-symmetric composite laminates with temperature provides a measure of the magnitude of the thermal stresses and the mechanical behavior of the material with temperature. In the present work, an experimental method based on the pioneer use of a digital camera and image processing method is proposed to perform such measurements. Taking advantage of the method and by comparing experimental and CLT, extended-CLT and FEM simulation results, an evaluation of the residual stresses is described and an approach providing more precise determination of the residual thermal stresses in non-symmetric laminates is proposed.     

Benchmark test of the effectiveness of a nitrogen cooled beryllium reflector-filter

We present a comparison between the calculated and the measured effectiveness of a nitrogen cooled beryllium reflector-filter in increasing the cold flux of a polyethylene moderator at the same temperature. We also discuss the impact of the quality of beryllium on the results.