Assessment of interatomic parameters for the reproduction of borosilicate glass structures via DFT-GIPAW calculations

Borates and borosilicates are potential candidates for the design and development of glass formulations with important industrial and technological applications. A major challenge that retards the pace of development of borate/borosilicate based glasses using predictive modeling is the lack of reliable computational models to predict the structure-property relationships in these glasses over a wide compositional space. A major hindrance in this pursuit has been the complexity of boron-oxygen bonding due to which it has been difficult to develop adequate B–O interatomic potentials. In this article, we have evaluated the performance of three B–O interatomic potential models recently developed by Bauchy et al [J. Non-Cryst. Solids, 2018, 498, 294–304], Du et al [J. Am. Ceram. Soc. https://doi.org/10.1111/jace.16082 ] and Edèn et al [Phys. Chem. Chem. Phys., 2018, 20, 8192–8209] aiming to reproduce the short-to-medium range structures of sodium borosilicate glasses in the system 25 Na₂O x B₂O₃ (75 − x) SiO₂ (x = 0-75 mol%). To evaluate the different force fields, we have computed at the density functional theory level the NMR parameters of ¹¹B, ²³Na, and ²⁹Si of the models generated with the three potentials and the simulated MAS NMR spectra compared with the experimental counterparts. It was observed that the rigid ionic models proposed by Bauchy and Du can both reliably reproduce the partitioning between BO₃ and BO₄ species of the investigated glasses, along with the local environment around sodium in the glass structure. However, they do not accurately reproduce the second coordination sphere of silicon ions and the Si–O–T (T = Si, B) and B-O-T distribution angles in the investigated compositional space which strongly affect the NMR parameters and final spectral shape. On the other hand, the core-shell parameterization model proposed by Edén underestimates the fraction of BO₄ species of the glass with composition 25Na₂O 18.4B₂O₃ 56.6SiO₂ but can accurately reproduce the shape of the ¹¹B and ²⁹Si MAS-NMR spectra of the glasses investigations due to the narrower B–O–T and Si-O-T bond angle distributions. Finally, the effect of the number of boron atoms (also distinguishing the BO₃ and BO₄ units) in the second coordination sphere of the network former cations on the NMR parameters have been evaluated.     

Comprehensive studies on polyethylenimine filled polypropylene and its potential application in carbon dioxide sequestration

Polypropylene (PP) was blended with branched polyethylenimine (PEI) with the aim to prepare blends having CO₂ adsorption property. The CO₂ adsorption properties will be conferred due to the presence of variety of amine functionality in PEI. PEI contains primary, secondary as well as tertiary amine groups. Before testing CO₂ adsorption, PP–PEI blends were characterized using variety of techniques, for example, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, scanning electron microscopy, and polarized light optical microscopy. In this work, we have studied in detail both compatibilized as well as noncompatibilized blends of PP and PEI. The compatibilization was achieved via addition of maleic anhydride grafted PP. Finally, all the compatibilized as well as noncompatibilized blends were studied for CO₂ adsorption. The compatibilized blends showed better thermal, mechanical as well as CO₂ adsorption properties as compared to the noncompatibilized blends. POLYM. ENG. SCI., 59:2092–2102, 2019. © 2019 Society of Plastics Engineers     

Complex impedance studies of low temperature synthesized fine grain PZT/CeO2 nanocomposites

Fine grain nanocomposites of (100 ? x) PbZr_0.52Ti_0.48O₃ ? (x) CeO₂ with x = 0.5, 1 and 2 wt%, were prepared and characterized for structural and microstructural changes. Addition of ceria nanoparticles resulted into a fine grain microstructure with average grain size ranging from 600 nm to 440 nm and a significant decrease in sintering temperature (～200 °C). Size distribution profile, as analyzed by lognormal distribution function suggests a very narrow size distribution. X-ray diffraction analyses of sintered samples reveal that fine grain PZT/CeO₂ nanocomposite could retain distorted tetragonal structure even with grain size as low as 440 nm. Further, complex impedance spectroscopy studies were performed to illustrate the electrical properties of bulk and grain boundary phases in fine grain ceramics. Two electrical processes in the impedance spectra at temperatures above 350 °C were attributed to bulk and grain boundary phase. Magnitude of grain boundary capacitance and corresponding transition was found to be strongly dependent on grain size of the system. Both bulk and grain boundary relaxation processes follows Arrhenius law.     

A comprehensive modeling framework for gate stack process dependence of DC and AC NBTI in SiON and HKMG p-MOSFETs

A comprehensive modeling framework involving mutually uncorrelated contribution from interface trap generation and hole trapping in pre-existing, process related gate insulator traps is used to study NBTI degradation in SiON and HKMG p-MOSFETs. The model can predict time evolution of degradation during DC and AC stress, time evolution of recovery after stress, impact of stress and recovery bias and temperature, and impact of several AC stress parameters such as pulse frequency, duty cycle, duration of last pulse cycle (half or full) and pulse low bias. The model can successfully explain experimental data measured using fast and ultra-fast methods in SiON and HKMG devices having different gate insulator processes. The trap generation and trapping sub components of the composite model have been verified by independent experiments. Data published by different groups are reconciled and explained. The model can successfully predict long time DC and AC stress data and has been used to determine device degradation at end of life as EOT is scaled for different HKMG devices.     

A mixed integer programming formulation and effective cuts for minimising schedule durations of Australian truck drivers

Transport companies seek to maximise vehicle utilisation and minimise labour costs. Both goals can be achieved if the time required to fulfil a sequence of transportation tasks is minimised. However, if schedule durations are too short drivers may not have enough time for recuperation and road safety is impaired. In Australia transport companies must ensure that truck drivers can comply with Australian Heavy Vehicle Driver Fatigue Law and schedules must give enough time for drivers to take the amount of rest required by the regulation. This paper shows how transport companies can minimise the duration of truck driver schedules complying with Australian Heavy Vehicle Driver Fatigue Law. A mixed integer programming formulation is presented and valid inequalities are given. Computational experiments show that these inequalities provide significant reduction in computational effort when using one of the most advanced commercial mixed integer programming solver.     

A provably secure and efficient two‐party password‐based explicit authenticated key exchange protocol resistance to password guessing attacks

Password‐based two‐party authenticated key exchange (2PAKE) protocol enables two or more entities, who only share a low‐entropy password between them, to authenticate each other and establish a high‐entropy secret session key. Recently, Zheng et al. proposed a password‐based 2PAKE protocol based on bilinear pairings and claimed that their protocol is secure against the known security attacks. However, in this paper, we indicate that the protocol of Zheng et al. is insecure against the off‐line password guessing attack, which is a serious threat to such protocols. Consequently, we show that an attacker who obtained the users' password by applying the off‐line password guessing attack can easily obtain the secret session key. In addition, the protocol of Zheng et al. does not provide the forward secrecy of the session key. As a remedy, we also improve the protocol of Zheng et al. and prove the security of our enhanced protocol in the random oracle model. The simulation result shows that the execution time of our 2PAKE protocol is less compared with other existing protocols. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of phyllanthus emblica biodiesel based lubricant on cylinder liner and piston ring

In the present time, need of biogenic lubricants is the focusing area which will be biodegradable, avirulent and eco-friendly. Current experimental tests depict the effect of ‘Phyllanthus emblica’ a non-edible feedstock through pin on disc tribo tester. Tests were conducted to evaluate the impact of 0, 10, 20 and 30 % blending of Phyllanthus emblica with SAE20W40 lubricating oil on cylinder liner and piston ring. Promising results have been manifested with 10 % blending of biodiesel (BD) with lubricating oil in terms of coefficient of friction and specific wear rate in comparison with other examined feedstock. For analysis of wear debris in the used oil analytical ferrography was also done. The effects of temperature on wear and friction characteristics have also been discussed.

     

Numerical investigation of heat transfer and friction factor in ribbed triangular duct solar air heater using Computational fluid dynamics (CFD)

Journal of Mechanical Science and Technology - The Computational fluid dynamics (CFD) based analysis is carried out to investigate the thermal and hydraulic performance of circular rib roughened...     

Design and analysis of an improved smartcard‐based remote user password authentication scheme

With the fast development of the Internet and the telecommunication technologies, internet users are carrying out various electronic transactions over internet by means of the authentication protocols. To ensure efficient and robust online transaction, security of authentication protocol turns out to be a great concern nowadays. As a result, smartcard‐based password authentication and session key agreement scheme receives significant attention in recent years. In the literature, various authentication schemes have been proposed by the cryptographic research community. Recently, Li et al. analyze some security weaknesses of the authentication scheme of Chen et al. and propose an enhancement based on the discrete logarithm problem and computational Diffie–Hellman problem. This paper further cryptanalyzes the scheme of Li et al. and identifies various security loopholes and then constructs a modified authentication scheme as a remedy. The security and efficiency evaluations demonstrate that our scheme has more security features and low computation costs than the related schemes. Copyright © 2014 John Wiley & Sons, Ltd.     

Design methodologies for high-performance noise-tolerant XOR-XNOR circuits

Scaling down to deep submicrometer (DSM) technology has made noise a metric of equal importance as compared to power, speed, and area. Smaller feature size, lower supply voltage, and higher frequency are some of the characteristics for DSM circuits that make them more vulnerable to noise. New designs and circuit techniques are required in order to achieve robustness in presence of noise. Novel methodologies for designing energy-efficient noise-tolerant exclusive-OR-exclusive- NOR circuits that can operate at low-supply voltages with good signal integrity and driving capability are proposed. The circuits designed, after applying the proposed methodologies, are characterized and compared with previously published circuits for reliability, speed and energy efficiency. To test the driving capability of the proposed circuits, they are embedded in an existing 5-2 compressor design. The average noise threshold energy (ANTE) is used for quantifying the noise immunity of the proposed circuits. Simulation results show that, compared with the best available circuit in literature, the proposed circuits exhibit better noise-immunity, lower power-delay product (PDP) and good driving capability. All of the proposed circuits prove to be faster and successfully work at all ranges of supply voltage starting from 3.3 V down to 0.6 V. The savings in the PDP range from 94% to 21% for the given supply voltage range respectively and the average improvement in the ANTE is 2.67X.