An improved timestamp-based remote user authentication scheme

To protect the remote server from various malicious attacks, many authentication schemes have been proposed. Some schemes have to maintain a password verification table in the remote server for checking the legitimacy of the login users. To overcome potential risks of verification tables, researchers proposed remote user authentication schemes using smartcard, in which the remote server only keeps a secret key for computing the user’s passwords and does not need any verification table for verifying legal user. In 2003 Shen, Lin, and Hwang proposed a timestamp-based password authentication scheme using smartcards in which the remote server does not need to store the passwords or verification table for user authentication. Unfortunately, this scheme is vulnerable to some deadly attacks. In this paper, we analyze few attacks and finally propose an improved timestamp-based remote user authentication scheme. The modified scheme is more efficient and secure than original scheme.     

Dendrimer as nanocarrier for drug delivery

Dendrimers are novel three dimensional, hyperbranched globular nanopolymeric architectures. Attractive features like nanoscopic size, narrow polydispersity index, excellent control over molecular structure, availability of multiple functional groups at the periphery and cavities in the interior distinguish them amongst the available polymers. Applications of dendrimers in a large variety of fields have been explored. Drug delivery scientists are especially enthusiastic about possible utility of dendrimers as drug delivery tool. Terminal functionalities provide a platform for conjugation of the drug and targeting moieties. In addition, these peripheral functional groups can be employed to tailor-make the properties of dendrimers, enhancing their versatility. The present review highlights the contribution of dendrimers in the field of nanotechnology with intent to aid the researchers in exploring dendrimers in the field of drug delivery.     

Investigations of Wear Response of Pure Mg and Mg-0.4 Ce-Y2O3/ZnO Nanocomposites Using a Single and Repeated Scratch Tests

ABSTRACT

This work examines the micrometer-scale wear behavior of pure Mg and its composites at various loads (100–500 mN) under single and multiple scratch conditions. The Mg-0.4Ce alloy reinforced with nanoparticles of zinc oxide (ZnO) and yttrium oxide (Y₂O₃) is investigated. The effect of reinforcement addition on wear characteristics and the coefficient of friction (COF) was evaluated. Moreover, the influence of number of scratches on wear quantification and wear mechanism was deduced at different loads. The results suggest that both the mechanical and tribological performance of ZnO-reinforced composite is significantly better than that of the Y₂O₃-reinforced composite, which can be attributed to a low COF and higher strengthening due to ZnO addition.     

Attentional networks for music generation

Realistic music generation has always remained as a challenging problem as it may lack structure or rationality. In this work, we propose a deep learning based music generation method in order to produce old style music particularly JAZZ with rehashed melodic structures utilizing a Bi-directional Long Short Term Memory (Bi-LSTM) Neural Network with attention. Owing to the success in modelling long-term temporal dependencies in sequential data and its success in case of videos, Bi-LSTMs with attention serves as a natural choice and early utilization in music generation. We validate in our experiments that Bi-LSTMs with attention are able to preserve the richness and technical nuances of the music performed.

     

Experimentally measured thermal transport properties of aluminum–polytetrafluoroethylene nanocomposites with graphene and carbon nanotube additives

Reactive materials such as aluminum (Al) and polytetrafluoroethylene (Teflon) are used for energy generation applications and specifically in ordnance technologies. With the advent of nanotechnology various nano-scale additives have become incorporated into reactive material formulations with the hope of enhanced performance. An important component to the study of energy generation is an examination of energy transport through a reactant matrix. This study examines an experimental approach to quantifying thermal properties of an Al/Teflon nanocomposite reactant matrix that has been impregnated with carbon additives. Various structures of carbon are investigated and include amorphous nanoscale carbon spheres (nano C), graphene flakes and unaligned multiwalled carbon nanotubes (CNTs). The additives were selected based on their completely different structures with the hypothesis that the structure of the additive will influence the thermal transport properties of the matrix. Results show graphene has the greatest influence on the thermophysical properties. For example, thermal conductivity of the composites containing graphene increased by 98%. Graphene similarly enhanced the thermal diffusivity and specific heat of the Al/Teflon matrix. Conversely, nano C and CNTs decreased the thermal conductivity and thermal diffusivity of the samples significantly.     

Graft copolymerization of acrylamide–methylacrylate comonomers onto cellulose using ceric ammonium nitrate

The graft copolymerization of acrylamide–methylacrylate comonomers was carried out using ceric ammonium nitrate as initiator in the presence of nitric acid at 25 ± 1°C. The effects of feed molarity, feed composition, reaction time, and temperature on graft yield (%G) and other grafting parameters were investigated. The determination of rate of ceric (IV) ions disappearance as a function of feed molarity and reaction time was useful in the determination of the rate of ceric (IV) ions consumption during graft copolymerization. The graft yield (%G) in the presence of acrylamide increases because of the synergistic effect of acrylamide comonomer. The composition of the grafted chains (F_AAm) varies on varying the feed composition and reaction temperature but is almost constant during feed molarity variation. The Mayo and Lewis method was used to determine the reactivity ratios of acrylamide (r₁) and methylacrylate (r₂), which are 0.65 and 1.07, respectively. The product of reactivity ratio (r₁ r₂) is less then unity; hence, an alternate arrangement of comonomer blocks in the grafted copolymer chain is proposed. The rate of graft copolymerization of comonomers onto cellulose is second power to the concentration of comonomers and square root to the concentration of ceric ammonium nitrate. Suitable reaction steps for graft copolymerization of comonomers onto cellulose are proposed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2631–2642, 2002     

Graft copolymerization of acrylamide onto cellulose in presence of comonomer using ceric ammonium nitrate as initiator

The graft copolymerization of acrylamide (AAm) and ethylmethacrylate (EMA) monomers onto cellulose has been carried out using ceric ammonium nitrate (CAN) as initiator in presence of nitric acid at (25 ± 1)°C and varying feed molarity from 7.5 × 10^?2 mol dm^?3 to 60.0 × 10^?2 mol dm^?3 at fixed feed composition (f_AAm = 0.6). The graft yield (%G_Y) has shown a linear increasing trend upto a feed molarity of 37.5 × 10^?2 mol dm^?3. The composition of grafted copolymer chains was found to be constant (F_AAm = 0.56) during feed molarity variation but shown variations with feed composition (f_AAm) and reaction temperature. The grafting parameters have shown increasing trends up to 7.5 × 10^?3 mol dm^?3 concentration of ceric (IV) ions and decreased on further increasing the concentration of ceric (IV) ions beyond 7.5 × 10^?3 mol dm^?3. The IR and elemental analysis data were used to determine the composition of grafted chains (F_AAm) and reactivity ratio of acrylamide (r₁) and ethylmethacrylate (r₂) comonomers. The reactivity ratio for acrylamide (r₁) and ethylmethacrylate (r₂) has been found to be 0.7 and 1.0 respectively, which suggested for an alternate arrangement of average sequence length of acrylamide (mM?₁) and ethylmethacrylate (mM?₂) in grafted chains. The rate of graft copolymerization of comonomers onto cellulose was found to be proportional to square concentration of comonomers and square root to the concentration of ceric (IV) ions. The energy of activation (ΔEa) of graft copolymerization was found to be 9.57 kJ mol^?1 within the temperature range of 20–50°C. On the basis of experimental findings, suitable reaction steps have been proposed for graft copolymerization of selected comonomers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2546–2558, 2006     

High power linearized RF phase shifter using anti-series diodes

We present the design and development of a new reflection-type phase shifter (RTPS) that uses anti-series diodes to achieve high linear output power. Using this topology, the PS provides a continuous phase shift of 180/spl deg/ at 1.88GHz. The measured 1-dB compressed RF output power (P/sub 1 dB/) available from the PS is greater than 28dBm over the entire phase-control range.     

Electro-oxidation and determination of gemcitabine hydrochloride,an anticancer drug at gold electrode

Electrochemical behavior of an anticancer drug, gemcitabine hydrochloride (GMB) was studied in 10.4 pH with 0.2 M phosphate buffer solution as supporting electrolyte at 25 ± 0.1 °C at gold electrode (GE) using different voltammetric techniques. The electrochemical process was observed to be diffusion controlled, irreversible and involving one-electron oxidation. Under optimal conditions, the peak current was proportional to GMB concentration in the range of 0.1–15 μM with a detection limit of 0.06 μM by differential pulse voltammetry. The method was developed for the determination of GMB in pharmaceutical formulations and urine as a real sample.