Supervised Learning in Spiking Neural Networks with Phase-Change Memory Synapses

Spiking neural networks (SNN) are artificial computational models that have been inspired by the brain's ability to naturally encode and process information in the time domain. The added temporal dimension is believed to render them more computationally efficient than the conventional artificial neural networks, though their full computational capabilities are yet to be explored. Recently, computational memory architectures based on non-volatile memory crossbar arrays have shown great promise to implement parallel computations in artificial and spiking neural networks. In this work, we experimentally demonstrate for the first time, the feasibility to realize high-performance event-driven in-situ supervised learning systems using nanoscale and stochastic phase-change synapses. Our SNN is trained to recognize audio signals of alphabets encoded using spikes in the time domain and to generate spike trains at precise time instances to represent the pixel intensities of their corresponding images. Moreover, with a statistical model capturing the experimental behavior of the devices, we investigate architectural and systems-level solutions for improving the training and inference performance of our computational memory-based system. Combining the computational potential of supervised SNNs with the parallel compute power of computational memory, the work paves the way for next-generation of efficient brain-inspired systems

Design and real time implementation of nonlinear sliding surface with the application of super-twisting algorithm in nonlinear sliding mode control for twin rotor MIMO system

This paper proposes the design of a nonlinear sliding surface based on the principle of variable damping concept for 2-degree of freedom Twin Rotor Multiple input Multiple output System (2-dof TRMS). The implementation of the designed nonlinear sliding surface in real time is demonstrated. Super-twisting algorithm is applied in nonlinear sliding mode control. The nonlinear sliding surface enables the system trajectory to be highly robust and with the application of super-twisting algorithm in nonlinear sliding mode controller (SMC), the designed controller has minimized the problem of chattering considerably. The system is modeled in such a way that it includes all nonlinearities and coupling effects. A decoupler is designed to nullify the coupling effect. This scheme is capable of reducing both the settling time and peak overshoot simultaneously for 2-dof TRMS. The scheme also reduces the chattering. The proposed method is compared with the design using PID controller. The applicability of the designed nonlinear sliding surface and nonlinear SMC with super-twisting algorithm have been tested both in simulation and in real time. This research paper is mainly dealing with the modeling of Twin rotor MIMO system by including all nonlinearities and coupling effects, the decoupler design for 2-dof TRMS, the design of nonlinear sliding surface for 2-dof TRMS and application of super-twisting algorithm in nonlinear sliding mode control for 2-dof TRMS

Effect of Diode Laser in the Treatment of Chronic Periodontitis: A Clinical and Microbiological study

BACKGROUND : Periodontitis is an inflammatory disease of the periodontium. The most commonly used treatment modality involves scaling and root planing. However, some microorganisms remain on the root surface even after root planing and scaling procedures. The properties of Lasers, such as monochromaticity, directionality and coherence make them unique and suitable for use in medical and dental fields. Recently, lasers have been put to use in procedures such as, pocket decontamination for treating periodontal disease. AIM : The aim of this study was to evaluate the effect of diode laser as an adjunct to scaling and root planing in the treatment of chronic periodontitis based on clinical and microbiological parameters at baseline and 3 months. MATERIALS AND METHODS : The study included 12 patients with chronic periodontitis, whose age ranged from 25 to 50 years. Following full mouth scaling and root planing, subgingival plaque samples were collected using sterile Gracey curettes, to test for microorganisms using multiplex PCR at baseline and at 3 months. A diode laser which operated at a wavelength of 970±15 nm with and having a power output of 2 watts, was used for pocket decontamination. RESULTS : Both test and control groups demonstrated no statistically significant improvements in PlI (p = 0.814), GI (p = 0.814), PD (p = 0.071) and CAL (p = 0.183) from baseline to 3 months. At 3 months, there was no statistically significant difference in the clinical parameters between test and control groups, suggesting that adjunctive use of diode laser did not seem to have any added benefit over conventional SRP. The PCR test for A.a (p= 0.564) and T.f (p = 0.414) demonstrated no significant improvement in the test group when compared to the control group. CONCLUSION : The results obtained in this study suggest that diode laser offered no significant benefit over conventional scaling and root planing as regards to the clinical and microbiological parameters that were assessed 3 months post operatively

Response of Dome-enclosed Box-type Structure to Underwater Explosion

In the development of underwater sensor systems, the sensor arrays are configured for different shapes like cylindrical, rectangular and spherical depending on the requirement. The rectangular shaped box–type structure discussed here has both top and bottom ends open. Flanges stiffen the top and bottom ends, and gussets are used to connect the flanges with the structure. In this paper, the box-type structure is subjected to non-contact underwater explosion in a shock tank to study the peak free field pressure on the structure. To simulate the actual conditions, the structure is placed in free flooded area and covered with a dome. The free-field peak pressure on the dome and structure are plotted with time. The measured pressure curves are in agreement with the empirical predictions reported in literature. It is concluded that around 85 per cent of the shock impulse acting on the dome is transmitted to the box-type structure. The dome and box-type structure withstood the explosive load, thereby validating their design.Defence Science Journal, 2013, 63(4), pp.381-385, DOI:http://dx.doi.org/10.14429/dsj.63.213