Faculty Publications
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Item Gesture Recognition using Viola Jones Framework and Contour Detection(Institute of Electrical and Electronics Engineers Inc., 2017) Karthik, S.; Ramesh, K.; Prakash, S.B.; Murthy, Y.V.S.; Koolagudi, S.G.The work in this paper suggests a method to recognize gestures of a hand using the approaches of contour detection and Viola Jones framework. At initial stage, hand detection algorithm has been applied to detect the hand using machine learning approach. Later, the methods of contour detection and convex hull are considered for gesture recognition. The system has been trained with variety of gestures and hands with different hand positions. © INDIACom-2017.Item A survey of design techniques for conversational agents(Springer Verlag service@springer.de, 2017) Ramesh, K.; Ravishankaran, S.; Joshi, A.; Chandrasekaran, K.A conversational agent also referred to as chatbot is a computer program which tries to generate human like responses during a conversation. Earlier chatbots employed much simpler retrieval based pattern matching design techniques. However, with time a number of new chatbots evolved with an aim to make it more human like and hence to pass the Turing test. Now, most of the chatbots employ generative knowledge based techniques. This paper will discuss about various chatbot design techniques, classification of chatbot and discussion on how the modern chatbots have evolved from simple pattern matching, retrieval based model to modern complex knowledge based models. A table of major conversational agents in chronological order along with their design techniques is also provided at the end of the paper. © Springer Nature Singapore Pte Ltd. 2017.Item Thermal stability and crystallization kinetics of Bi doped Si15Te85-xBix (0 ≤ x ≤ 2) chalcogenide glassy alloys(Elsevier Ltd, 2018) Fernandes, B.; Munga, P.; Ramesh, K.; Udayashankar, N.K.Bulk Si15Te85-xBix (0 ≤ x ≤ 2) chalcogenide glassy alloys were prepared by well-established melt quenching technique. Thermal stability and crystallization kinetics of these alloys were investigated by employing differential scanning calorimetry (DSC) technique at different heating rates, namely, 10, 15, 20 and 25 K/min under non-isothermal condition. Thermal parameters such as glass transition (Tg), onset crystallization (Tc) and peak crystallization (Tp) temperatures were observed. Double crystallization peaks observed in the DSC thermogram refer to the instability and phase separated network in the glasses. Various kinetic parameters such as thermal stability (ΔT), enthalpy (ΔHc), entropy (ΔS), specific heat (ΔCp) and fragility index are deduced. The calculated kinetic parameters suggest that the stability of glassy samples decreases with the increase in Bi addition. The activation energies of glass transition (Eg), and crystallization (Ec) are calculated using relevant kinetic formulae. We further discuss on the kinetics of the synthesized materials relevant for their applications in phase change memory (PCM) material. © 2017 Elsevier Ltd.Item Electrical switching and thermal behavior of ternary Si15Te85-xBix (0 ≤ x ≤ 2) chalcogenide glasses(Elsevier Ltd, 2018) Fernandes, B.; Munga, P.; Ramesh, K.; Udayashankar, N.K.Bulk semiconducting Si15Te85-xBix(0 ≤ x ≤ 2) chalcogenide glasses have been prepared using a well established melt-quenching technique. Electrical switching studies have been undertaken on Si15Te85-xBix(0 ≤ x ≤ 2) chalcogenide glasses. The results indicate that these samples exhibit memory type electrical switching behavior. It has been observed that the switching voltage VT of the glasses decreases with the addition of Bi. In addition, thermal stability and OFF state resistivity of the samples have been found to decrease with the increase in Bi concentration and are related to the observed decrease in switching voltages. The switching voltage (VT) has been found to increase with the thickness of the sample and decrease with increase in temperature confirming the thermal origin of the memory switching process. Further, scanning electron microscopy (SEM) studies reveal the formation of a crystalline channel indicating the conducting path between the two electrodes in the switched region. © 2018 Elsevier Ltd. All rights reserved.Item Memory type switching behavior of ternary Ge20Te80-xSnx (0 x 4) chalcogenide compounds(Institute of Physics Publishing michael.roberts@iop.org, 2016) Fernandes, B.J.; Sridharan, K.; Pumlianmunga, P.; Ramesh, K.; Udayashankar, N.K.Chalcogenide compounds have gained huge research interest recently owing to their capability to transform from an amorphous to a crystalline phase with varying electrical properties. Such materials can be applied in building a new class of memories, such as phase-change memory and programmable metallization cells. Here we report the memory type electrical switching behavior of a ternary chalcogenide compound synthesized by doping Tin (Sn) in a germanium-telluride (Ge20Te80) host matrix, which yielded a composition of Ge20Te80-xSnx (0 x 4). Results indicate a remarkable decrease in the threshold switching voltage (V T) from 140 to 61 V when the Sn concentration was increased stepwise, which is attributed to the domination of the metallicity factor leading to reduced amorphous network connectivity and rigidity. Variation in the threshold switching voltage (V T) was noticed even when the sample thickness and temperature were altered, confirming that the memory switching process is of thermal origin. Investigations using x-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed the formation of a crystalline channel that acts as the conduction path between the two electrodes in the switched region. Structural and morphological studies indicated that Sn metal remained as a micro inclusion in the matrix and hardly contributed to the rigid amorphous network formation in Ge20Te80-xSnx. Memory type electrical switching observed in these ternary chalcogenide compounds synthesized herein can be explored further for the fabrication of phase-change memory devices. © 2016 IOP Publishing Ltd.Item Crystallization kinetics of Sn doped Ge20Te80?xSnx (0 ? x ? 4) chalcogenide glassy alloys(Elsevier Ltd, 2017) Fernandes, B.J.; Naresh, N.; Ramesh, K.; Sridharan, K.; Udayashankar, N.K.Chalcogenide semiconductors have evolved as multifunctional materials due to their fascinating thermal, optical, electrical and mechanical properties. In this report, Ge20Te80?xSnx (0 ? x ? 4) glassy alloys are systematically studied in order to understand the effect of variation of Sn content on the thermal parameters such as glass transition (Tg) onset crystallization (Tc), peak crystallization (Tp), melting temperature (Tm), activation energy of glass transition (Eg), and crystallization (Ec). The values of Eg are calculated from the variation of Tg with the heating rate (?), according to Kissinger and Moynihan model, while the values of Ec are calculated from the variation of Tp with the heating rate (?), according to Kissinger, Takhor, Augis-Bennett and Ozawa model. Thermal stability and glass forming ability (GFA) are discussed for understanding the applicability of the synthesized materials in phase change memory (PCM) applications. Thermal parameters are correlated with the electrical switching studies to get an insight into the phase change mechanism. The results of the calculated thermal parameters reveal that the GFA of the synthesized Ge20Te80?xSnx (0 ? x ? 4) glassy alloys has a synchronous relationship with their thermal properties studied through differential scanning calorimetry, indicating their potential for phase-change memory device applications. © 2017 Elsevier B.V.Item Electrical switching in Si20Te80 ? xBix (0 ? x ? 3) chalcogenide glassy alloys(Elsevier B.V., 2018) Fernandes, B.J.; Ramesh, K.; Udayashankar, N.K.Chalcogenide glasses have attained enormous research interest due to their importance in finding electronic memories. Here we report electrical switching and thermal crystallization behavior of Si20Te80 ? xBix (0 ? x ? 3) glasses. We observe a significant decrease in the threshold voltage (VT) and the thermal stability (?T), indicating that in Si20Te80 ? xBix glasses, the resistivity of the additive element Bi plays a dominant role over network connectivity/rigidity. The variation of VT with respect to thickness and temperature of the sample indicates that the memory switching observed in Si20Te80 ? xBix glasses is influenced by the thermally induced transitions (thermal mechanism). Scanning electron microscopy (SEM) studies on pre-switched and post switched samples reveal the morphological changes on the surface of the sample, and serve as an experimental evidence for the formation of the crystalline filament between two electrodes during switching. Furthermore, the decrease in ?T values indicates that the Si-Te glasses become de-vitrifiable more easily with the addition of Bi, influencing the decrease of VT. Structural evaluation like thermal devitrification studies and morphological changes elucidate the restricted glass formability of the studied glass system. © 2018 Elsevier B.V.Item Crystallization kinetics of Si20Te80?xBix (0???x???3) chalcogenide glasses(Elsevier Ltd, 2019) Fernandes, B.J.; Ramesh, K.; Udayashankar, N.K.In this report, we investigate the crystallization kinetics of Si20Te80?xBix (0 ? x ? 3) chalcogenide glassy systems using differential scanning calorimetry (DSC) technique. Systematic studies are carried out in order to understand the variation of thermal parameters such as glass transition temperature (Tg), onset crystallization temperature (Tc) and peak crystallization temperature (Tp) as a function of composition. Activation energy for glass transition (Eg) and crystallization (Ec) has been calculated based on the relevant statistical methods. Furthermore, thermal parameters such as change in specific heat (?Cp), fragility index (F), thermal stability (?T)& (S), enthalpy (?Hc), entropy (?S) are deduced to interpret distinct material behaviour as a function of composition. Structural evaluation like thermal devitrification studies elucidate the restricted glass formability of the studied glass system. Conclusively, a relationship has been established between the obtained thermal parameters and electrical switching characteristics. © 2019 Elsevier B.V.