Processing and Properties of TiB2 with MoSi2 Sinter-additive: A First Report

The densification of non-oxide ceramics like titanium boride (TiB₂) has always been a major challenge. The use of metallic binders to obtain a high density in liquid phase-sintered borides is investigated and reported. However, a non-metallic sintering additive needs to be used to obtain dense borides for high-temperature applications. This contribution, for the first time, reports the sintering, microstructure, and properties of TiB₂ materials densified using a MoSi₂ sinter-additive. The densification experiments were carried out using a hot-pressing and pressureless sintering route. The binderless densification of monolithic TiB₂ to 98% theoretical density with 2–5 μm grain size was achieved by hot pressing at 1800°C for 1 h in vacuum. The addition of 10–20 wt% MoSi₂ enables us to achieve 97%–99%ρ_th in the composites at 1700°C under similar hot-pressing conditions. The densification mechanism is dominated by liquid-phase sintering in the presence of TiSi₂. In the pressureless sintering route, a maximum of 90%ρ_th is achieved after sintering at 1900°C for 2 h in an (Ar+H₂) atmosphere. The hot-pressed TiB₂–10 wt% MoSi₂ composites exhibit high Vickers hardness (∼26–27 GPa) and modest indentation toughness (∼4–5 MPa·m^1/2).     

Electrochemical corrosion and materials properties of reactively sputtered TiN/TiAlN multilayer coatings

TiN/TiAlN multilayers of 2 μm thickness were successfully prepared by reactive DC magnetron sputtering method. XRD pattern showed the (1 1 1) preferential orientation for both TiN and TiAlN layers. XPS characterization showed the presence of different phases like TiN, TiO₂, TiON, AlN and Al₂O₃. Cross sectional TEM indicated the columnar growth of the coatings. The average RMS roughness value of 4.8 nm was observed from AFM analysis. TiN/TiAlN coating showed lower friction coefficient and lower wear rate than single layer coatings. The results of electrochemical experiments indicated that a TiN/TiAlN multilayer coating has superior corrosion resistance in 3.5% NaCl solution.     

Atomistic insights into solvation dynamics and conformational transformation in thermo-sensitive and non-thermo-sensitive oligomers

Solvation dynamics and conformational transformation in oligomers with varying degree of temperature sensitivity is studied using molecular dynamics (MD) simulations. Conformational transformation in three model systems namely poly(N-isopropylacrylamide) (PNIPAM), poly(acrylamide) (PAA), and poly(ethylene glycol) (PEG) are compared and contrasted to understand the origin of a coil-to-globule transformations across the lower critical solution temperature (LCST) in thermo-sensitive oligomers. PNIPAM, PAA, and PEG are water-soluble oligomers. However, for the temperature range used in these simulations, PNIPAM shows an LCST whereas PAA and PEG are non-thermo-sensitive. Oligomers of PNIPAM, PAA, and PEG consisting of 30 monomer units (30-mer) each were simulated at 5 °C (278 K) and 37 °C (310 K). Conformational transformations in the oligomers are evaluated using structural and dynamical correlation functions such as radius of gyration, radial distribution function, residence time probabilities and hydrogen-bonding life-times. Our simulations suggest that the solubility, solvation dynamics, and conformation of the oligomers are dictated by two factors: (a) the local structure of proximal water and (b) the diffusion and exchange kinetics of proximal water with bulk water. In thermo-sensitive oligomer such as PNIPAM, we find that the coil-to-globule transition is closely related to the local ordering and solvation dynamics of PNIPAM. We have identified stable configurations of proximal water molecules for an oligomer undergoing conformational transition. The slow diffusional properties of proximal water molecules near PNIPAM oligomers suggests that water forms a stable network near hydrophilic groups of PNIPAM as compared to the hydrophilic groups of PAA and PEG. Thermal perturbation of this solvated structure results in significant reduction in local ordering of water, which contributes to the globular collapse and the reduced solubility of PNIPAM above its LCST. On the other hand, non-thermo-sensitive oligomers such as PAA and PEG are characterized by much faster diffusion and exchange kinetics of proximal water at the two simulated temperatures compared to PNIPAM. This faster exchange kinetics helps in maintaining higher hydration level of the oligomers and is responsible for the apparent hydrophilic character and thereby the observed solubility at the two simulated temperatures.     

Low Velocity Impact,Fatigue and Visco-elastic Behaviour of Carbon/E-glass Intra-ply fibre-Reinforced Nano-silica Toughened Epoxy Composite

Silicon - This current research dealing the effect of adding high stiffness carbon fibre along with E-glass fibre and addition of nano-silica particles as a toughening agent in epoxy resin. The...     

Application of Proteomics in Pancreatic Ductal Adenocarcinoma Biomarker Investigations: A Review

Pancreatic ductal adenocarcinoma (PDAC), a highly aggressive malignancy with a poor prognosis is usually detected at the advanced stage of the disease. The only US Food and Drug Administration-approved biomarker that is available for PDAC, CA 19-9, is most useful in monitoring treatment response among PDAC patients rather than for early detection. Moreover, when CA 19-9 is solely used for diagnostic purposes, it has only a recorded sensitivity of 79% and specificity of 82% in symptomatic individuals. Therefore, there is an urgent need to identify reliable biomarkers for diagnosis (specifically for the early diagnosis), ascertain prognosis as well as to monitor treatment response and tumour recurrence of PDAC. In recent years, proteomic technologies are growing exponentially at an accelerated rate for a wide range of applications in cancer research. In this review, we discussed the current status of biomarker research for PDAC using various proteomic technologies. This review will explore the potential perspective for understanding and identifying the unique alterations in protein expressions that could prove beneficial in discovering new robust biomarkers to detect PDAC at an early stage, ascertain prognosis of patients with the disease in addition to monitoring treatment response and tumour recurrence of patients.     

Application of simulated lidar scanning patterns to constrained Gaussian turbulence fields for load validation

We demonstrate a method for incorporating wind velocity measurements from multiple‐point scanning lidars into three‐dimensional wind turbulence time series serving as input to wind turbine load simulations. Simulated lidar scanning patterns are implemented by imposing constraints on randomly generated Gaussian turbulence fields in compliance with the Mann model for neutral stability. The expected efficiency of various scanning patterns is estimated by means of the explained variance associated with the constrained field. A numerical study is made using the hawc2 aeroelastic software, whereby the constrained turbulence wind time series serves as input to load simulations on a 10 MW wind turbine model using scanning patterns simulating different lidar technologies—pulsed lidar with one or multiple beams—and continuous‐wave lidars scanning in three different revolving patterns. Based on the results of this study, we assess the influence of the proposed method on the statistical uncertainty in wind turbine extreme and fatigue loads. The main conclusion is that introducing lidar measurements as turbulence constraints in load simulations may bring significant reduction in load and energy production uncertainty, not accounting for any additional uncertainty from real measurements. The constrained turbulence method is most efficient for prediction of energy production and loads governed by the turbulence intensity and the thrust force, while for other load components such as tower base side‐to‐side moment, the achieved reduction in uncertainty is minimal. Copyright © 2016 John Wiley & Sons, Ltd.     

Identification of loading conditions resulting in roller slippage in gearbox bearings of large wind turbines

The dynamic loads on the rollers inside the bearings of large wind turbine gearboxes operating under transient conditions are presented with a focus on identifying conditions leading to slippage of rollers. The methodology was developed using a multi‐body model of the drivetrain coupled with aeroelastic simulations of the wind turbine system. A 5 MW reference wind turbine is considered for which a three‐stage planetary gearbox is designed on the basis of upscaling of an actual 750 kW gearbox unit. Multi‐body dynamic simulations are run using the ADAMS software using a detailed model of the gearbox planetary bearings to investigate transient loads inside the planet bearing. It was found that assembly and pre‐loading conditions have significant influence on the bearing's operation. Also, the load distribution in the gearbox bearings strongly depends on wind turbine operation. Wind turbine start‐up and shut‐down under normal conditions are shown to induce roller slippage, as characterized by loss of contacts and impacts between rollers and raceways. The roller impacts occur under reduced initial pre‐load on opposite sides of the load zone followed by stress variation, which can be one of the potential reasons leading to wear and premature bearing failures. Copyright © 2017 John Wiley & Sons, Ltd.     

First and second law analyses of a typical solar air dryer system: a case study

This communication presents an experimental study based on energy and exergy analyses of a typical solar air dryer. On the basis of the experimental results, the first and the second law efficiencies are calculated with respect to the available solar radiation. It is found that the second law efficiency is much less than the first law efficiency irrespective of the mass flow rate of the circulating fluid. It is also found that both efficiencies are an increasing function with respect to the mass flow rate of the working fluid. For a particular day, it is also found that first and second law efficiencies fluctuate according to radiation. The results obtained in this article are found to be consistent with those obtained by earlier authors as given in the literature.     

Secure Key Agreement with Rekeying Using FLSO Routing Protocol in Wireless Sensor Network

Wireless Personal Communications - A challenge in wireless sensor network (WSN) is to design an energy efficient and secure network protocol because sensors are the wireless device with limited...     

Enhanced photoluminescence of CoWO<Subscript>4</Subscript> in CoWO<Subscript>4</Subscript>/PbWO<Subscript>4</Subscript> nanocomposites

CoWO₄/PbWO₄ nanocomposites were successfully synthesized at room temperature (RT) by co-precipitation route without using any templates or surfactants and sintered at 600 °C for good crystallization. The sintered samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy and Zeta potential measurements. UV–Visible diffuse reflectance spectroscopy, photoluminescence (PL) and PL lifetime were studied at RT. The results indicate that the composites have two-phase composition: CoWO₄ and PbWO₄. SEM micrograph and zeta potential measurements reveal particle agglomeration. The intrinsic PL peak emission at 467 nm of CoWO₄ nano sample was enhanced upto four times by optimizing the atomic ratio of Pb/Co concentration. The interconnected interface of CoWO₄/PbWO₄ nanocomposites could have led to increase in number of recombination of electron hole pairs in CoWO₄ and enhanced its intrinsic PL emission intensity. The mechanism of enhanced PL emission for the CoWO₄/PbWO₄ nanocomposites can be attributed to charge transfer between [WO₄]^2? and [WO₆]^6? complexes due to intra particle agglomeration leading to possible interface.