An Experimental Insight into the Structural and Electronic Characteristics of Strontium‐Doped Titanium Dioxide Nanotube Arrays

The possibility of in situ doping during electrochemical anodization of titania nanotube arrays is demonstrated and the mechanism and variations in structural and electronic characteristics of the nanotube arrays as after doping is systematically explored. In the presence of strontium as the dopant, bulk analysis shows strontium mainly incorporated into the lattice of TiO₂. Surface analysis, however, reveals phase segregation of SrO in the TiO₂ matrix at high Sr doping levels. The near edge X‐ray absorption fine structure (NEXAFS) spectroscopy analysis reveals that Sr²⁺ doping only alters the Ti and O ions interaction in the TiO₂ lattice on the surface with no effect on their individual charge states. An in‐depth understanding of the dopant incorporation mechanism and distribution into TiO₂ nanotube arrays is achieved using high resolution transmission electron microscopy (HRTEM) and the high angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) coupled with the electron energy loss spectroscopy (EELS) measurements on the surface and bulk of the nanotubes. Upon their use to photoelectrochemically split water, the Sr‐doped TiO₂ nanotube film shows incident photon conversion efficiencies (IPCE) as high as 65%. The enhanced light activity in conjunction with the ordered one‐dimensional morphology makes the fabricated films promising candidates for water photoelectrolysis.     

Effect of variations in thermophysical properties and design parameters on the performance of a V-shaped micro grooved heat pipe

The paper presents a detailed simulation of a V-shaped micro heat pipe. The effect of the substrate temperature on the model has been considered. A new method for calculating dry-out length has been proposed. The sensitivity of the model to variations in thermophysical properties and design parameters has been studied. The variations in the contact angle for the substrate-coolant liquid system, surface tension and viscosity of the coolant liquid, inclination, groove angle, length of adiabatic section and radius of ungrooved substrate have been considered. The effect of design and operating parameters on the performance of the heat pipe has been studied. The variations in contact angle have been found to significantly affect the performance of a micro heat pipe. The performance of a micro heat pipe is susceptible to ungrooved area of a V-shaped micro heat pipe. If the groove is not sharp enough i.e., the radius of ungrooved substrate is more; the micro heat pipe may cease to work even before it reaches its other operating limits. The various sensitivity studies made in this work gives better understanding of variations in thermophysical properties and design parameters of a micro heat pipe.     

On the control of chaos via fractional delayed feedback method

In this paper the problem of controlling unstable fixed points (in discrete systems) and periodic orbits (in continuous system) is investigated via a new scheme involving fractional derivatives. This method is based on applying feedback of measured states and using the period of fixed points and periodic orbits. In this method there is no need of information for fixed point and periodic orbits, just the period is enough. The effectiveness of this method is investigated via some demonstrative example.     

Color image encryption based on DNA encoding and pair coupled chaotic maps

Information security has become a significant issue in encryption due to the rapid progress of internet and network. Therefore, the development of the encryption algorithm is a growing and significant problem. In this study, a new color image encryption was introduced based on DNA complementary rules and pair coupled chaotic maps. At first, the plain color image was divided into three components (R, G, B) being converted into three DNA matrices using DNA encoding rules. Secondly, DNA addition for R, G and B components was implemented and scrambled the elements position of three DNA sequence via the pair coupled chaotic maps. Three gray coded images obtained and RGB encrypted image was achieved by restructuring R, G, B components. The simulation of experimental result and security analysis showed that this algorithm had larger secret key space and strong secret key sensitivity and it had excellent ability to resist against statistical and differential attacks.

     

Molecularly Capped Omniphobic Polydimethylsiloxane Brushes with Ultra-Fast Contact Line Dynamics

Droplet friction is common and significant in any field where liquids interact with solid surfaces. This study explores the molecular capping of surface-tethered, liquid-like polydimethylsiloxane (PDMS) brushes and its substantial effect on droplet friction and liquid repellency. By exchanging polymer chain terminal silanol groups for methyls using a single-step vapor phase reaction, the contact line relaxation time is decreased by three orders of magnitude–from seconds to milliseconds. This leads to a substantial reduction in the static and kinetic friction of both high- and low-surface tension fluids. Vertical droplet oscillatory imaging confirms the ultra-fast contact line dynamics of capped PDMS brushes, which is corroborated by live contact angle monitoring during fluid flow. This study proposes that truly omniphobic surfaces should not only have very small contact angle hysteresis, but their contact line relaxation time should be significantly shorter than the timescale of their useful application, i.e., a Deborah number less than unity. Capped PDMS brushes that meet these criteria demonstrate complete suppression of the coffee ring effect, excellent anti-fouling behavior, directional droplet transport, increased water harvesting performance, and transparency retention following the evaporation of non-Newtonian fluids.     

Development of asphalt cements for road pavement using sustainable nanomaterials: A review

In today's world, transportation infrastructure plays a vital role in global competitiveness and quality of life in societies. The pavement industry deals with tremendous amounts of construction materials. Thus, even a small improvement in the technology can lead to significant environmental benefits and a reduction in the life-cycle cost of road networks. Asphalt cement is an integral part of road pavement construction, and despite favorable properties at the processing temperature, some challenges need to be addressed to reduce cost and improve performance. This review discusses the nanocellulose modification of asphalt cement for pavement application. Three primary cellulose-based nanoparticles were studied, including bacterial cellulose, cellulose nanofibers, and cellulose nanocrystals, and their applications in asphalt cement modification. Various research results show significant improvement in pavement's rheological and performance properties with the help of cellulose-based nanoparticles. However, this review provides the reader with an objective evaluation of the benefits and practical challenges ahead of the industrial-scale application of nanocellulose in the pavement industry.     

Recovery of residual emulsifiable oil from waste water by flotation

A source of waste‐water pollution in machining is the lubricating/cooling fluid used. This study investigates the application of the flotation technique for the removal of emulsifiable oil. Research has been carried out on a process of selective separation of oil using mixtures of anionic/nonionic surfactants as collectors and a cationic surfactant as a de‐emulsifier (coagulant). The behaviour of the mixtures at the aqueous solution‐air interface has been studied, and the critical micelle concentration, efficiency, effectiveness, minimum surface area, and free energy of micellisation determined. The effect of the optimum mole fraction of the mixtures on oil separation has been discussed from the point of view of physical parameters. The selectivity achieved can be explained in terms of surfactant concentration and the structure of the micelles.     

Investigation of mixing performance in a semi-active T-micromixer actuated by magnetic nanoparticles: Characterization via Villermaux–Dushman reaction

A semi-active T-type micromixer is designed to intensify micromixing by actuating magnetic nanoparticles (MNPs). Five permanent magnets in a zig-zag arrangement are located next to the mixing channel of the micromixer to apply the magnetic field to the fluid flow. Micromixing performance is considered in terms of the segregation index (X_S) by the Villermaux/Dushman reaction test. The effects of magnetic flux intensity (B = 380–500 mT), the concentration of MNPs (φ = 0.002–0.01 [w/v]), and flow rate ratios on X_S and pressure drop are investigated. By increasing MNPs concentration from φ = 0.002–0.008 (w/v), X_S decreased and the rise in φ up to 0.008 (w/v) has not been significant on X_S. Maximum mixing efficiency (i.e., minimum X_S = 0.0088) is achieved for B = 500 mT and φ = 0.01 (w/v). By applying the magnetic field, the mixing performance increased due to the motion of MNPs, but its negative effect is an increase in the pressure drop along the micromixer reactor. Generally, with the formation of MNPs barriers inside the mixing channel, the main fluid flows through these layers and creates the sinusoidal flow paths compared to no magnetic field conditions, and thus, a superior mixing efficiency could be attained.     

Activated nitriles in heterocyclic synthesis: A Novel Synthesis of Pyrimidine Derivatives

The reaction of 3-amino-2,4-diethoxycarbonylcrotononitrile with cinnamonitrile derivatives afforded the pyrimidines 5a--d and not the pyridines 4 as expected from literature. Similarly pyrimidines 5e--h were produced when 3-amino-2,4-dicyanocrotononitrile was treated with the same reagent. The structure was established based on MS and high resolution ¹H-n.m.r. spectroscopy.