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Broadly tunable wideband optical single sideband generation using self-coupled silicon resonator
No full textWe propose and demonstrate a tunable broadband optical single sideband generation using self-coupled silicon micro-ring resonator. We exploit self-coupling in a ring cavity to generate tunable resonance splitting. Using the proposed device, single sideband with carrier signal is generated from a double sideband signal. Experimental verification of power fading tree transmission through a 43 km signal mode optical fiber is achieved for an RF frequency range of 1-20 GHz, extendible to higher frequencies. We also achieved a spurious free dynamic range of > 99.9 +/- 1.05 dB.Hz(2/3) over the demonstrated frequency range. Furthermore, error-free data transmission of 1-12 Gbps over a 43 km fiber is also demonstrated with a detailed analysis of bit error rate as well. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen
A Tabletop Diffuse Optical Tomographic (DOT) Experimental Demonstration System
No full textDiffuse Optical Tomographic (DOT) experimental studies are performed in a dark environment, surrounded by dedicated instruments to acquire quality measurement data for the better image reconstruction. Hence, DOT experimental setups are bulky and educational experimental demonstration of DOT to the public in an open space is challenging. The International Year of Light (IYL2015), motivated us to develop a DOT demonstration system to improve public understanding of the role of light in medical imaging. In this paper, we present a tabletop DOT system, that has four NIR light sources, six silicon-photodiode detectors, a control circuitry containing a 24-bit dual sigma-delta ADC with an ARM cortex-M3 processor and a MatLab based image reconstruction software. The control circuitry controls the light source and detector selections, measures diffused light and sends data to a laptop computer via USB for the low-resolution 2D DOT image reconstruction. The imaging domain was a tissue mimicking Intralipid and India ink solution in a circular tank, with a variable inhomogeneity location. We evaluated the system performance by demonstrating it on IISc Open Day an annual event opened for the general public in India. We performed interactive experimental demonstrations by allowing the audiences to place an optical inhomogeneity in the homogeneous phantom tank at their desired location. Our system was capable of localizing inhomogeneity in the reconstructed image from the experimental measurement data within a few seconds. The system was proven to be instrumental in demonstrating all of the basic principles and working principle of the DOT imaging in an interactive manner
Synchronization of Hes1 oscillations coordinates and refines condensation formation and patterning of the avian limb skeleton
No full textThe tetrapod appendicular skeleton is initiated as spatially patterned mesenchymal condensations. The size and spacing of these condensations in avian limb buds are mediated by a reaction-diffusion-adhesion network consisting of galectins Gal-1A, Gal-8 and their cell surface receptors. In cell cultures, the appearance of condensations is synchronized across distances greater than the characteristic wavelength of their spatial pattern. We explored the possible role of observed oscillations of the transcriptional co-regulator Hes1 in this phenomenon. Treatment of micromass cultures with DAPT, a gamma-secretase inhibitor, damped Hes1 oscillations, elevated Gal-1A and -8 mRNA levels, and led to irregularly-sized proto-condensations that subsequently fused. In developing limb buds, DAPT led to spatially non-uniform Hes1 expression and fused, truncated and misshapen digits. Periodicity in adhesive response to Gal-1A, a plausible Hes1-dependent function, was added to a previously tested mathematical model for condensation patterning by the two-galectin network. The enhanced model predicted regularization of patterning due to synchronization of Hes1 oscillations and resulting spatiotemporal coordination of its expression. The model also predicted changes in galectin expression and patterning in response to suppression of Hes1 expression, which were confirmed in in vitro experiments. Our results indicate that the two-galectin patterning network is regulated by Hes1 dynamics, the synchronization of which refines and regularizes limb skeletogenesis
Unprecedented 30 K hysteresis across switchable dielectric and magnetic properties in a bright luminescent organic-inorganic halide (CH6N3)(2)MnCl4
No full textMultifunctional materials that exhibit various switchable properties and simultaneously feature excellent luminescent properties boast tremendous technological importance. However, realization of such materials is still elusive, as integration of these independent yet technologically important properties in single materials is fairly challenging. Here, we report a new highly photoluminescent hybrid (CH6N3)(2)MnCl4 (CH6N3 = guanidinium cation, GC) that exhibits an unprecedented 30 K wide hysteresis in dielectric and magnetic switching across the structural phase transition (SPT). The compound uniquely features trimeric (Mn3Cl12)(6-) units composed of face-sharing MnCl6 octahedra in its zero-dimensional crystal structure and undergoes a thermally induced reversible structural transition at 166/195 K. The high and low dielectric states show a remarkable 30 K wide reversible dielectric switching which is mainly portrayed by the relative population of quadrupolar and dipolar moments of disordered and ordered phases of GCs. Only a small change in the crystal volume across the transition is reflected in subtle magnetic switching. Moreover, the material exhibits an intense orange-red emission under ultraviolet excitation at room temperature with long lifetime (1.71 ms) and large quantum yield (39.5%). This report suggests a promising strategy to construct truly multifunctional optoelectronic materials and may be helpful to improve the understanding and control of switchable physical properties and luminescence in supramolecular materials
Towards Behavioural Cloning for Autonomous Driving
No full textThis paper proposes an off-policy imitation learning methodology for autonomous driving using a doubly-deep recurrent convolutional architecture that learns compositional representations in both space and time domains. The architecture has been referred to as NAVNet (Navigation Network) and is end-to-end trainable. The recurrent long-term models are directly connected with the visual convolutional models. The models can be trained together to learn both temporal dynamics as well as the convolutional perceptual representations. The approach is non-data driven in nature and the system learns a regression-based mapping function between input images and steering angle. Results presented in this research indicate distinct advantages of the proposed LRCN model over the state-of-the-art deep learning techniques for autonomous navigation
Rheology of a suspension of conducting particles in a magnetic field
No full textWhen a suspension of conducting particles is sheared in a magnetic field, the fluid vorticity causes particle rotation. Eddy currents are induced in a conductor rotating in a magnetic field, resulting in magnetic moment, and a magnetic torque due to the external field. In the absence of inertia, the angular velocity of a particle is determined from the condition that the sum of the hydrodynamic and magnetic torques is zero. When the particle angular velocity is different from the fluid rotation rate, the torque exerted by the particles on the fluid results in an antisymmetric particle stress. The stress is of the form . p /D j!j.. 1 / c.O V !O /C . 2 / c O V. H O !O.!O H O //=. q 1 H O /2 /C . 3 / c.!O H O H O !O /= q 1 H O /2 /, where ! is the fluid vorticity at the centre of the particle, !O and H O are the unit vectors in the direction of the fluid vorticity and the magnetic field, O is the third order Levi-Civita antisymmetric tensor and . 1 / c, . 2 / c and . 3 / c are called the first, second and third couple stress coefficients. The stress proportional to . 1 / c is in the plane perpendicular to !O, that proportional to . 2 / c is in the plane perpendicular to the unit normal to !O in the !O -H O plane, and that proportional to . 3 / c is in the !O -H O plane. A relation . 2 / c D H O . 1 / c = q 1 H O /2 /results from the condition that the component of the eddy current torque along the magnetic field is zero. The couple stress coefficients are obtained for two geometries, a uniform spherical particle of radius R and a thin spherical shell of radius R and thickness ffi R with ffi 1, in the dilute (non-interacting) limit in the absence of fluid inertia. These couple stress coefficients are functions of two dimensionless parameters, D. 0H2 0 = 4 pj!j/, the ratio of the characteristic magnetic and hydrodynamic torques, and fi, the product of the vorticity and current relaxation time. Here 0 is the magnetic permeability, H0 is the magnetic field and is the fluid viscosity. The parameter fi has the form fi p D.j!j 0R2 = 2 %/for a uniform particle and fi s D.j!j 0R2 ffi= 2 %/for a thin shell, where % is the electrical resistivity. Scaled couple stress coefficients are defined, 1 D.. 1 / c =.. 3 = 2 /. 1.!O H O /2 /// and 3 D.. 3 / c =.. 3 = 2 /!O H O q 1 H O /2 //, which are independent of the fluid viscosity and the particle volume fraction, and which do not depend on !O and H O in the limits 1 and 1. Here, is the volume fraction of the particles. Asymptotic analysis is used to determine the couple stress coefficients in the limits 1 and 1, and a numerical solution procedure is formulated for 1. For 1, the particle angular velocity is aligned close to the fluid vorticity, and the scaled couple stress coefficients are times a function of fi. For 1, the particle angular velocity is aligned close to the magnetic field, 1 ! 1 and 3 / 1. When the magnetic field is perpendicular to the fluid vorticity, !O H O D 0, the particle angular velocity is aligned along the vorticity, and only the first couple stress coefficient is non-zero. For high fi, there are multiple solutions for the couple stress coefficient. Multiple steady states are also observed for a near perpendicular magnetic field, !O H O <. 1 = 3 /, for a reason different from that for a perpendicular magnetic field. Asymptotic analysis is used to explain the existence of multiple steady states in both cases
Analytical Expression for Resonances of an Inhomogeneous, Radial, Lossless LC Network
No full textThis paper is a sequel to the authors' previous work wherein an analytical expression was derived for the harmonic sum of squares of natural frequencies of a lossless LC ladder network, which is a widely accepted means to model a single, isolated winding for analyzing impulse behavior. The present paper extends the previous result, so that it is applicable to multiple windings in actual transformers. The complexities of the previous work, viz., inhomogeneity and an exhaustive consideration of inductive coupling are retained, and additionally all possible capacitive couplings are now considered. Furthermore, the topology considered in this paper is generic enough to accommodate inductive branches emerging from any node. To the best of authors' knowledge, there exists no compact closed-form expression to relate the natural frequencies to the inductances and capacitances for a network having this extent of arbitrariness in topology. The success of this method can be ascribed to careful inspection of the inductance matrix to identify hidden pattern and/ or structure, followed by their deft manipulation guided by the basic law of mutual coupling between inductors. Interestingly, even a physical meaning can be assigned to each term of the derived expression, and this is done with the intention of assisting its use to conjure new applications
Rankin Cohen brackets on Jacobi forms of several variables and special values of certain Dirichlet series
No full textWe construct certain Jacobi cusp forms of several variables by computing the adjoint of linear map constructed using Rankin-Cohen-type differential operators with respect to the Petersson scalar product. We express the Fourier coefficients of the Jacobi cusp forms constructed, in terms of special values of the shifted convolution of Dirichlet series of Rankin-Selberg type. This is a generalization of an earlier work of the authors on Jacobi forms to the case of Jacobi forms of several variables
Digestive-Ripening-Facilitated Nanoengineering of Diverse Bimetallic Nanostructures
No full textFrom an ingenious methodology for obtaining monodispersity, digestive ripening has advanced to become an outstanding solution-based synthesis route to realizing various bimetallic heterostructures. This feature article attempts to provide an overview of the various facets of the codigestive ripening process and the array of heterostructures that could be achieved by this technique. We briefly discuss the mechanism of digestive ripening in the case of monometallic elements and use that understanding to elucidate the mechanism of the less well established codigestive ripening strategy for designing bimetallic nanostructures. The systems studied by our group in the past decade for the fabrication of diverse heterostructures are highlighted in this article. The exploitation of digestive ripening to realize monodisperse bimetallic nanostructures by several other groups is also featured. In addition to digestive ripening agents, the significance of tuning various reaction parameters and its consequences on the final structure and morphology have also been discussed. Additionally, efforts based on theoretical studies to gain insight into the factors which dominate the mechanism of the digestive ripening process have also been covered. This article is a contribution to the understanding of the codigestive ripening methodology and a demonstration of its tremendous potential in achieving the desired bimetallic heteronanostructures
An algorithmic approach to South Indian classical music
No full textWe develop a theoretical framework for representation and automated generation of South Indian classical music. The foundational part of the latter is based on symbolic dynamics and is implemented by translating the lexicographic rules for a raga to constraints on a Markov chain whose state space is a layered graph. We analyze the statistical properties of this Markov chain from the point of view of information theory. We also develop several tools in music signal processing, such as, (a) a procedure for automated generation of gamakas or ornamental notes, unique to South Indian classical music, (b) rhythm synchronization, and (c) an algorithm for perceptual scale shifts. The Online Supplement has computer synthesized music from sankarabharadna raga, rhythm synchronized music for a Mohana raga composition, original and synthesized gamakas over madhyama for Begadda and Nilambari ragas, and perceptually scale shifted ragas Hindodla, Madhyamavati, suddha saveri, and Udaya ravi chandrika ragas from the base Mohana raga