An IND-CCA2 Secure Certificateless Hybrid Signcryption

This article proposes a hybrid certificateless signcryption scheme that is secure against adaptive chosen ciphertext adversary in the random oracle model. The scheme combines an asymmetric encryption which is one way against chosen plaintext attack and any One-Time secure symmetric encryption scheme, combined using Fujisaki–Okamoto transformation. Uncommon to many Fujisaki–Okamoto based constructions which ensure message integrity alone, this scheme provides entity authentication in addition. By the choice of a hash function that utilizes the advantage of sponge based construction, the scheme enables the user to incorporate any One-Time secure symmetric encryption by re-configuring the input/output parameters. Fujisaki–Okamoto transformation, which is currently a standard in hybrid constructions, guarantees the indistinguishability against adaptive chosen ciphertext attack. The provision for choosing symmetric encryption in the scheme enables it to be implemented in all sort of cryptographic requirements including those in wireless communication.

     

Interleaving-Based Cyclic Delay Diversity OFDM Systems over Spatially Correlated Channels

Cyclic delay diversity employing multiple transmit antenna provides increased frequency selectivity and thereby improves the frequency diversity in coded orthogonal frequency division multiplexing (OFDM). However, spatial correlation due to insufficient spacing between transmit antennas degrades the diversity performance. In this paper, the correlation of effective channel frequency response (CFR) of CDD OFDM is analysed and then propose constellation rotation and adjacent interleaving (CRAI) scheme over spatially correlated channel. In the proposed scheme, the subcarrier constellation is rotated by a known angle and then imaginary parts of rotated adjacent subcarriers are interleaved. The squared Euclidean distance of the codewords is derived to show the effect of constellation rotation. Adjacent interleaving is shown to exploit the frequency diversity by reducing the variation in average channel power (ACP) due to spatial correlation. Simulation results reveal that the proposed scheme performs well in spatial correlated channel and thereby improves the bit error rate (BER) performance.     

Evaluation of Biodegradation of Pineapple Leaf Fiber Reinforced PVA Composites

Composites of polyvinyl alcohol (PVA) reinforced with different weight percentages of pineapple leaf fibers (PALF) were fabricated and evaluated for biodegradation by soil burial test and plate test. FTIR analysis indicated the existence of a chemical interaction between PVA and PALF. The water uptake study showed that the composites with higher fiber content displayed high tensile strength and brittleness but possessed lower water uptake potential. In the soil burial test, the composites with low matrix to filler ratios exhibited higher rates of degradation as evident by the associated decrease in molecular weights. Plate test performed using Pseudomonas putida showed that the composites were susceptible for degradation by bacteria. The results of this study indicated that PALF-reinforced PVA composites were completely biodegradable and could find potential applications in industries such as agriculture and packaging and safely disposed after use without causing environmental damage.     

Recent developments in the fire retardancy of polymeric materials

The widespread applications of polymeric materials require the use of conventional flame retardants based on halogen and phosphorous compounds to satisfy fire safety regulatory standards. However, these compounds, particularly halogen-based examples, are persistent organic pollutants of global concern and generate corrosive/toxic combustion products. To account for eco-friendliness, ultimate mechanical/physical properties and processing difficulties, the window of options has become too narrow. Although the incorporation of non-toxic nanofillers in polymers shows positive potential towards flame retardancy, many obstacles remain. Moreover, most of the literature on these materials is qualitative, and often points to conflicting/misleading suggestions from the perspectives of short-term and long-term fire exposure tests. Hence, there is a renewed need to fundamentally understand the fire response of such materials, and complement experimental results with theoretical modelling and/or numerical simulation.     

Imaging defects and junctions in single-walled carbon nanotubes by voltage-contrast scanning electron microscopy

Voltage-contrast scanning electron microscopy is demonstrated as a new technique to locate and characterize defects in single-walled carbon nanotubes. This method images the surface potential along and surrounding a nanotube in device configuration and it is used here to study the following: (a) structural point-defects formed during nanotube growth, (b) nano-scale gap formed by high-current electrical breakdown, (c) electronic defect such as electron-irradiation induced metal-insulator transition, and (d) charge injection into the substrate which causes hysteresis in nanotube devices. The in situ characterization of defect healing under high bias is also shown. The origin of voltage-contrast, the influence of the above defects on the contrast profiles and optimum imaging conditions are discussed.     

Ranking and Reranking with Perceptron

This work is inspired by the so-called reranking tasks in natural language processing. In this paper, we first study the ranking, reranking, and ordinal regression algorithms proposed recently in the context of ranks and margins. Then we propose a general framework for ranking and reranking, and introduce a series of variants of the perceptron algorithm for ranking and reranking in the new framework. Compared to the approach of using pairwise objects as training samples, the new algorithms reduces the data complexity and training time. We apply the new perceptron algorithms to the parse reranking and machine translation reranking tasks, and study the performance of reranking by employing various definitions of the margins.Editors: Dan Roth and Pascale Fung