Concept of an interlaced phased array for beam switching

A novel concept is described for feeding and phasing a large linear array of N antenna elements using only three or five feed points and phase shifters and still achieving beam switching. The idea consists of drastically reducing the number of input points by interlacing a small numer of serially fed subarrays which are suitably phased. This so-called interlaced phased array (IPA) concept was tested using an array of 15 four-element Yagi antennas with a spacing equal to 0.8 wavelengths and found feasible. Some of the distinct advantages of the IPA in comparison with a conventional system of beam switching are reduced power loss, reduced phasing errors, reduced cost, increased reliability resulting from greatly reduced number of phase shifters, and better symmetry of off-zenith beams     

Magnetism and 166Er Mössbauer spectroscopy of Er2−xPrxCo17

The bulk magnetic properties and ¹⁶⁶Er Mössbauer spectra of Er_2?xPr_xCo₁₇ pseudo-binaries are reported. Incorporation of Pr into Er₂Co₁₇ increases the anisotropy field (H_A) and the saturation magnetization, while resulting in only a slight (5%) decrease in the Curie temperature. The quadrupole interaction deduced from the Mössbauer spectrum suggests that Pr preferentially substitutes for Er in Er₂Co₁₇ at the 2d site. The rise in H_A is a consequence of the preferential substitution, which occurs because spatial constraints at the 2d site are less for the larger Pr³⁺ ion. Coupling between Er-Co and Pr-Co is found to be antiferromagnetic and ferromagnetic, respectively.     

A three-person cooperative game formulation of the world oil market

The world oil market is modelled as a three-person cooperative game in characteristic function form with and without side payments. The three players are the oil importing countries, the group in OPEC led by Iran and the group in OPEC led by Saudi Arabia. Various solutions of the games are studied such as the core, the Shapley value, the bargaining set and the nucleolus.     

Hyperfine structure of Γ6 electronic level in cubic Yb compound from Mössbauer spectroscopy

The hyperfine structure of the Γ₆ electronic level in the cubic compound Cs₂NaYbCl₆ has been observed from the Mössbauer studies of ¹⁷⁰Yb. The effective hyperfine coupling constant is found to be $\text{-10.9±0.1}\text{mm}\text{sec.}$     

Direct determination of uranium in seawater by laser fluorimetry

A method for estimation of uranium in seawater by using steady state laser flourimetry is described. Uranium present in seawater, in concentration of approximately 3 ng ml⁻¹ was estimated without prior separation of matrix. Quenching effect of major ions (Cl⁻, Na⁺, SO₄⁻, Mg⁺, Ca⁺, K⁺, HCO₃⁻, Br⁻) present in seawater on fluorescence intensity of uranium was studied. The concentration of phosphoric acid required for maximum enhancement of fluorescence intensity was optimized and was found to be 5%. Similarly the volume of concentrated nitric acid required to eliminate the quenching effect of chloride and bromide completely from 5 ml of seawater were optimized and was found to be 3 ml. A simple equation was derived using steady state fluorescence correction method and was used for calculation of uranium concentration in seawater samples. The method has a precesion of 1% (1 s, n = 3). The values obtained from laser fluorimetry were validated by analyzing the same samples by linear sweep adsorptive stripping voltametry (LSASV) of the uranium-chloranilic acid (2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone) complex. Both the values are well in agreement.     

Electronic and steric effects in binding of deep cavitands

A deep, self-folding cavitand responds to minor electronic differences between suitably sized adamantane guests. Binding constants range from <0.5 to 4000 M(-1) for guests as similar as 1-bromoadamantane and 1-cyanoadamantane. The barriers to guest exchange also vary up to 3 kcal mol(-1).     

Coulomb interactions and nanoscale electronic inhomogeneities in manganites

We study electronic inhomogeneities in manganites using simulations on a microscopic model with Coulomb interactions amongst two electronic fluids-one localized (polaronic), the other extended-and dopant ions. The long range Coulomb interactions frustrate phase separation induced by the large on site repulsion between the fluids. A single phase ensues which is inhomogeneous at a nanoscale, but homogeneous on mesoscales, with many features that agree with experiments. This, we argue, is the origin of nanoscale inhomogeneities in manganites, rather than phase competition or disorder effects.     

Tailoring of Electronic Structure and Thermoelectric Properties of a Topological Crystalline Insulator by Chemical Doping

Topological crystalline insulators (TCIs) are a new quantum state of matter in which linearly dispersed metallic surface states are protected by crystal mirror symmetry. Owing to its vanishingly small bulk band gap, a TCI like Pb_0.6Sn_0.4Te has poor thermoelectric properties. Breaking of crystal symmetry can widen the band gap of TCI. While breaking of mirror symmetry in a TCI has been mostly explored by various physical perturbation techniques, chemical doping, which may also alter the electronic structure of TCI by perturbing the local mirror symmetry, has not yet been explored. Herein, we demonstrate that Na doping in Pb_0.6Sn_0.4Te locally breaks the crystal symmetry and opens up a bulk electronic band gap, which is confirmed by direct electronic absorption spectroscopy and electronic structure calculations. Na doping in Pb_0.6Sn_0.4Te increases p‐type carrier concentration and suppresses the bipolar conduction (by widening the band gap), which collectively gives rise to a promising zT of 1 at 856 K for Pb_0.58Sn_0.40Na_0.02Te. Breaking of crystal symmetry by chemical doping widens the bulk band gap in TCI, which uncovers a route to improve TCI for thermoelectric applications.     

Authentication using Finger Knuckle Prints

Automated security is one of the major concerns of modern times. Secure and reliable authentication systems are in great demand. A biometric trait like the finger knuckle print (FKP) of a person is unique and secure. Finger knuckle print is a novel biometric trait and is not explored much for real-time implementation. In this paper, three different algorithms have been proposed based on this trait. The first approach uses Radon transform for feature extraction. Two levels of security are provided here and are based on eigenvalues and the peak points of the Radon graph. In the second approach, Gabor wavelet transform is used for extracting the features. Again, two levels of security are provided based on magnitude values of Gabor wavelet and the peak points of Gabor wavelet graph. The third approach is intended to authenticate a person even if there is a damage in finger knuckle position due to injury. The FKP image is divided into modules and module-wise feature matching is done for authentication. Performance of these algorithms was found to be much better than very few existing works. Moreover, the algorithms are designed so as to implement in real-time system with minimal changes.