Acid‐Controlled Chemodivergent Synthesis of Three Differently Substituted Quinolines via Site Selective Coupling of ortho‐ Aminoaryl Ketones with α‐Enolic Dithioesters

A straightforward approach for the chemodivergent synthesis of quinolines is described through site‐selective coupling of ortho‐aminoaryl ketones with α‐enolic dithioesters (DTEs) under solvent‐free conditions. The operationally and user‐simple one‐pot methodology is based on the trifunctional nature of DTEs. Both the carbonyl and the thiocarbonyl moiety in α‐enolic dithioesters were employed for the efficient construction of three differently substituted quinolines in a chemoselective manner simply by variation of an easy to handle acid catalyst.

     

Chaos,intermittency and control of bifurcation in a ZC2-DPLL

Nonlinear dynamics of a dual sampler-based zero crossing digital phase lock loop (ZC₂-DPLL) has been investigated. Analysis supported by detailed numerical studies shows that the system enters a chaotic state through a cascade of period doubling bifurcation. The dynamics of the system have been quantified with the dynamical measures of Lyapunov exponent and correlation dimension. Further, it has been found that for certain system parameters intermittency occurs in the system. The occurrence of intermittency has been proved using the Pomeau–Manneville principle. The phenomenon of bifurcation control in a ZC₂-DPLL using time delay feedback has been explored. It has been found that for some suitably chosen control parameters bifurcation phenomena can be controlled such that the stable locked zone of a bifurcation controlled ZC₂-DPLL can be extended, which enhances the application potentiality of a ZC₂-DPLL.     

Structural studies of Langmuir-Blodgett films: technology and analysis

Using the Langmuir-Blodgett technique, ultra-thin films of organic molecules can be deposited on suitable substrates with a high degree of precision over the individual layer thickness. The electronic and optical properties of these films are closely related to the molecular orientation within the layer. Some of the techniques used to analyse the structure of the floating and transferred layers are discussed in this short review, with special reference to phthalocyanine films     

Physical Metallurgy of Beryllium and Its Alloys

Some of the physical metallurgy aspects of beryllium and its alloys have been briefly described and discussed in this paper. To start with, many of the attractive properties of beryllium and some of its major applications have been mentioned. This is followed by a short discussion pertaining to the polymorphism of the metal and the stability of the relevant phases. The solid solution behaviour of beryllium and the formation of beryllium rich intermetallic phases have been dealt with subsequently. Some of the broad characteristics of the phase diagrams of binary beryllium systems have then been mentioned. A short account of beryllium based as well as beryllium containing alloys and composites has been provided after this. The next topic to be discussed is the deformation behaviour of the metal, with particular reference to slip systems, stacking faults, twinning modes and fracture modes. This is followed by a brief account of grain size effects and of recrystallization and grain growth in beryllium. Finally, the brittleness problem in beryllium has been discussed.     

Staggered Spin-Orbit Order: A New Paradigm of Broken Symmetry Phase of Matter

We propose a novel spin-orbit density wave order, which can arise in a variety of materials classes. In systems where the noninteracting wavefunctions are defined by an exotic quantum number such as total angular momentum, pseudospin, or helical quantum number owing to spin-orbit coupling of various natures, interaction can induce an emergent spin-orbit density wave even when time-reversal symmetry is intact. This density wave order is different from standard time-reversal breaking spin or orbital density wave. We apply this idea to explain the enigmatic “hidden order” phase in heavy fermion URu₂Si₂ as well as an unknown gapped quasiparticle state observed in two-dimensional electron gases, such as the surface state of BiAg₂.     

Role of aluminium addition on structure of Fe substituted Fe73·5 − x Si13·5B9Nb3Cu1Al x alloy ribbons

The investigation has dealt with the structure and magnetic properties of rapidly solidified and annealed Fe_73·5???x Si_13·5B₉Nb₃Cu₁Al _x (x?=?0, 2, 4, 6 at%) ribbons prepared by melt spinning. Complete amorphous structure was obtained in as-spun ribbons of x?=?0 and 2 at% compositions, whereas structure of ribbons containing higher Al was found to be partially crystalline. Detailed thermal analyses of the alloys and the melt spun ribbons revealed that the glass forming ability in the form of ${{ \textit{T}}}_{\mathbf{x}}{/}{{ \textit{T}}}_{\mathbf{l}}$ (ratio between crystallization and liquidus temperature) is the highest for 2 at% Al alloys and decreases with further addition of Al. Annealing of all as spun ribbons resulted in the precipitation of nanocrystalline phase embedded in amorphous matrix in the form of either ${ \textit{DO}}_{{ 3}}$ phase or bcc ${\upalpha}$ -Fe(Si/Al) solid solution depending on the initial composition of the alloy. Only bcc ${\upalpha}$ -Fe(Si/Al) solid solution was formed in 2 at% Al ribbons whereas ordered DO₃ structure was found to be stabilized in other ribbons including 0 at% Al. A detailed study on determination of precision lattice parameter of nanocrystalline phase revealed that the lattice parameter increases with the addition of Al indicating the partitioning behaviour of Al in nanocrystalline phase.     

Chaotic electronic oscillator from single amplifier biquad

The present letter reports a simple chaotic electronic oscillator. A single amplifier biquad (SAB) based active high-Q Band Pass Filter (BPF) is converted into a chaotic oscillator by introducing a single passive nonlinear element in the form of a general purpose pn junction diode, and a storage element in the form of an inductor. The chaotic circuit is mathematically modeled, which is a set of four coupled first-order autonomous nonlinear differential equations. The behavior of the proposed circuit is investigated through numerical simulations and electronic hardware experiments. It is found that the circuit shows complex behaviors, like, bifurcations and chaos, for a certain range of circuit parameters. The chaotic behavior of the circuit is ensured qualitatively by bifurcation diagram, phase plane plot and experimentally obtained power spectrum, and quantitatively by Lyapunov exponents and Kaplan–York dimensions.     

A MICROPROCESSOR BASED ULTRA HIGH SPEED PROTECTION SCHEME AGAINST OPEN CIRCUIT FAULT OF MULTI-BUS EHV/UHV TRANSMISSION SYSTEM

ABSTRACT

A modern power system consisting of multi-bus EHV/UHV transmission links to increase the capacity and reliability of the system, requires faster and reliable operation of relays and circuit breakers for its protection. The present day available relays for protection of transmission lines against open circuit fault are not sufficient for application in EHV/UHV circuits for their larger operating time. In the present paper, a microprocessor based ultra high speed relay has been developed for protection of a transmission line against open circuit fault which operates on the principle of continuous tracing of the line current waveforms thus eliminating sequence filters, and it requires less than one cycle to operate even in the worst possible fault condition. Application of a microprocessor enhances the accuracy, reliability and speed of operation of the device eliminating complicated hardware and dead band in operation. The use of zero crossing detectors in signal processing keeps the signals free from any transient effects.     

Improved graphitization and electrical conductivity of suspended carbon nanofibers derived from carbon nanotube/polyacrylonitrile composites by directed electrospinning

Single suspended carbon nanofibers on carbon micro-structures were fabricated by directed electrospinning and subsequent pyrolysis at 900 °C of carbon nanotube/polyacrylonitrile (CNT/PAN) composite material. The electrical conductivity of the nanofibers was measured at different weight fractions of CNTs. It was found that the conductivity increased almost two orders of magnitude upon adding 0.5 wt.% CNTs. The correlation between the extent of graphitization and electrical properties of the composite nanofiber was examined by various structural characterization techniques, and the presence of graphitic regions in pyrolyzed CNT/PAN nanofibers was observed that were not present in pure PAN-derived carbon. The influence of fabrication technique on the ordering of carbon sheets in electrospun nanofibers was examined and a templating effect by CNTs that leads to enhanced graphitization is suggested.     

Segregation of Magnesium and Calcium to the ( ) Prismatic Surface of Magnesium-Implanted Sapphire

Auger electron spectroscopy was used to study the segregation of magnesium and calcium to the prismatic plane of sapphire doped with Mg by ion implantation. Segregation behavior depended strongly upon the annealing atmosphere. Air annealing showed Mg segregation to the free surface whereas vacuum annealing resulted in no observable Mg cegregation above the detectability limit of our instrument. This is attributed to excessive vaporization of MgO at low oxygen pressures. In the absence of Mg on the surface, strong Ca segregation was observed although the bulk concentration of Ca was below 40 ppm, the total impurity level. The effective heat of segregation of Mg in air was found to be about -1.4 eV in the temperature range 1300° to 1550°C. The Ca coverage on the surface did not follow a Langmuir plot, probably because of Ca–Ca interaction at the larger surface concentrations. The implication of these results to the understanding of transport-related properties of impurity-doped alumina is discussed.