Now showing 1 - 10 of 105
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    Benchmarking the Poor Man's Ising Machine
    (01-01-2021)
    Umasankar, Gautham
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    Shah, Parth S.
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    We demonstrate the use of a Time-Multiplexed Opto-Electronic Oscillator based Coherent Ising Machine(CIM) to solve Maxcut Problems. Time multiplexing helps reduce system complexity and size, with good scaling against problem size. Benchmarks against state-of-the-art classical solvers show comparable performance, with encouraging results for further improvements.
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    Absorbing boundary layers for spin wave micromagnetics
    (15-03-2018)
    Venkat, G.
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    Fangohr, H.
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    Micromagnetic simulations are used to investigate the effects of different absorbing boundary layers (ABLs) on spin waves (SWs) reflected from the edges of a magnetic nano-structure. We define the conditions that a suitable ABL must fulfill and compare the performance of abrupt, linear, polynomial and tan hyperbolic damping profiles in the ABL. We first consider normal incidence in a permalloy stripe and propose a transmission line model to quantify reflections and calculate the loss introduced into the stripe due to the ABL. We find that a parabolic damping profile absorbs the SW energy efficiently and has a low reflection coefficient, thus performing much better than the commonly used abrupt damping profile. We then investigated SWs that are obliquely incident at 26.6°,45° and 63.4° on the edge of a yttrium-iron-garnet film. The parabolic damping profile again performs efficiently by showing a high SW energy transfer to the ABL and a low reflected SW amplitude.
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    Early vocabulary development through picture-based software solutions
    (01-01-2018)
    Kasthuri, G. R.
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    Ramanathan, P.
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    Jacob, N.
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    Assistive technology enables children with disabilities to gain access, function independently and take advantage of schooling and social opportunities[1]. The need for alternative and augmentative communication (AAC) in all children is not the same[2] but AAC can aid in expressive language and also support intelligible speakers in developing and using communication skills in varied situations. While the range and flexibility of AAC has grown over the years, making devices accessible to children at varied economic and regional backgrounds, is still a challenge. KAVI-PTS is designed as a picture-to-speech Android application, and has been made available in several Asian languages. This application is conceived of as an inexpensive software alternative to communication charts. It can be easily configured to adjust contrast levels and customize selection modes, enabling children to have access to a tailor-made communication solution.
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    Optofluidics based lab-on-chip device for in situ measurement of mean droplet size and droplet size distribution of an emulsion
    (20-01-2017)
    Shivhare, P. K.
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    There is an urgent need for a cost-effective, precise, and portable device for rapid and in situ measurement of the critical properties of an emulsion. Here, we report the development of such an optofluidic device for the measurement of mean droplet size (dMean) and droplet size distribution (DSD) of a water-in-oil emulsion. We formulated and detected water-in-oil droplets of much smaller dimensions (15μm) compared to the detection of larger droplets or plugs ( 100 μm to 300μm) reported in the literature, employing a cost effective and portable in-house built optical detection system. Use of the device for the measurement of the frequency of droplets from an on-chip droplet generator is demonstrated and validated using microscopy with excellent accuracy (2%). In addition, we provide some insight into the relatively high uncertainty in the collected signal in case of smaller droplets. The droplet size dD is characterized in terms of forward scatter signal and residence time T. We further argue that normalized residence time T of droplets in the detection zone which correlates linearly with droplet size dD is a better parameter to measure droplet size , compared to the forward scatter signal which vFSCM correlates nonlinearly with dD. Finally, the device is used to count the number of droplets of different size to predict dMean and DSD of emulsions. The results were compared with that obtained from traditional microscopy and a very good match (10-13%) was found, in contrast to previously reported non-portable off-chip methods that are 20-44% accurate. Thus, the reported device possesses high potential for accurate measurement of and DSD of emulsions in practical applications.
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    Charge estimation due to band mismatch in CPP GMR
    (01-12-2009)
    Vaidya, Varun
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    Sen, Srimoyee
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    We modify the macroscopic equations proposed by Valet and Fert for current perpendicular to the plane of a magnetic bilayer. Considering different spin bands for the spin-up and spin-down electrons, we calculate the charge accumulation near the interface along with the spin accumulation. This gives rise to a voltage drop at the interface, and causes the resistance to depend on the relative degree of magnetization of the two layers. We obtain expressions for the spatial distribution of charge and the accompanying electric field across the interface between the magnetic layers. An additional resistance caused by the potential step at the interface is added to get a better estimate of the magnetoresistance. ©2009 IEEE.
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    Mode-locked fibre laser damage on amplification due to multi-pulsing
    (23-09-2019)
    Khan, I.
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    Krishnamoorthy, S.
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    Semiconductor saturable absorber mirror based mode-locked fibre laser was built. On amplification, a chain action caused saturable absorber damage, initiated by backward amplified spontaneous emission, multi-pulsing and self-pulsing were reported.
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    Bit error rates in a frequency coded quantum key distribution system
    (15-09-2009)
    Kumar, Pradeep
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    The quantum bit error rate (QBER) is a measure of the performance of a frequency coded quantum key distribution system. We present a detailed analysis of the system, taking into account the statistics of light at different points in the link. We show that the statistics depends on the choice of phase of both the transmitter and receiver. We also evaluate the effects of crosstalk, out of band noise, and dark count of the gated avalanche photodetector on the QBER. Finally we use QBER to evaluate our implementation of the B92 protocol. © 2009 Elsevier B.V. All rights reserved.
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    Optimization, amplification and characterization of a passive mode-locked fibre laser
    (01-01-2019)
    Khan, S. I.
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    Sundar, S.
    An optimized passive mode locked fibre laser yielded optical pulses of 6.5 ps, 32 pJ. These increased to 27 nJ in two amplifier stages. An intensity auto-correlator was developed for monitoring the pulse-width.
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    Making Assistive Devices Affordable
    (01-10-2019) ;
    Indulakshmi, S.
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    Jeyaram, M.
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    Stalin, A. R.
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    Kasthuri, G.
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    Ramanathan, Prabha
    Cost effective indigenously developed assistive technology solutions are required to improve the lives of the differently-abled. Our low-cost assistive technology solutions aim to provide substantial support to the functional aspects that affect education, communication, employment, recreation and daily living. These include a number of solutions such as pressure sensitive ball and finger switches, a non-contact wireless (Blue-tooth) switch ADITI-W, gesture recognition using iGest, and a bluetooth enabled dual pad capacitive touch system, vPlay. These access switches have been developed, along with free and open source software, for physically challenged people and for people with special needs to access a computer. Software and Android applications such as Kavi PTS (Picture to Speech Communication app), Kavi (a web application to create lessons), and vBill (a billing app), were developed for independent communication, learning and employment respectively. Finally, a multi-lingual alternative and augmentative communication (AAC) hardware device, specifically for people who are non-verbal with motor impairments or those who are autistic has been developed. We also describe two devices for the visually impaired, namely, TakeNote and Tactograph. Through this paper we detail an entire suite of low cost affordable solutions that have been developed to address the multiple issues that address functional disability.
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    Relocking and Locking Range Extension of Partially Locked AMLL Cavity Modes with Two Detuned RF Sinusoids
    (01-07-2023)
    Krishnamoorthy, Shree
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    Actively mode-locked fiber ring lasers (AMLLs) with loss modulators are used to generate approximately (Formula presented.) pulses with (Formula presented.) repetition. RF detuning around the fundamental frequency, (Formula presented.), causes a loss in phase lock (unlocking) of cavity modes and partial mode locking. Multiple RF inputs are shown, theoretically, to relock and extend the locking range of cavity modes in a detuned partially mode-locked AMLL. A custom-built Yb (Formula presented.) -doped AMLL with (Formula presented.), and operating wavelength of (Formula presented.), was used to experimentally verify the theoretical predictions. Two RF sinusoidal signals with constant phase and equal amplitude resulted in an extension of the range by (Formula presented.) in addition to the range (Formula presented.) with single input for the mode (Formula presented.). An increase in locking range was also observed for higher modes. Pulsewidth reduction to approximately (Formula presented.) from about (Formula presented.) was also observed in the AMLL.