Browsing by Author "Mohan, S."

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CHARACTERIZING TEMPO CHANGE IN MUSICAL PERFORMANCES
(International Computer Music Association, 2011) Dannenberg, R.B.; Mohan, S.
Tempo change is an essential feature of live music, yet it is difficult to measure or describe because tempo change can exist at many different scales, from inter-beat-time jitter to long-term drift over several minutes. We introduce a piece-wise linear tempo model as a representation for tempo analysis. We focus on music where tempo is nominally steady, e.g. jazz and rock. Tapped beat data was collected for music recordings, and tempo was approximated as piece-wise linear functions. We compare the steadiness of tempo in recordings by accomplished, professional artists and in those by amateur artists, and show that professionals are steadier. This work offers new insights into the nature of tempo change based on actual measurements. In principle, improved models of tempo change can be used to improve beat tracking reliability and accuracy. In addition to technical applications, observations of music practice are interesting from a musicological perspective, and our techniques might be applied to a wide range of studies in performance practice. Finally, we present an optimal function approximation algorithm that that has broader applications to representation and analysis in many computer music applications. Â© 2011 ICMC. All Rights Reserved.
Deriving temporal trends in user preferences through short message strings
(2016) Deb, S.; Mohan, S.; Venkatraman, P.; Bindu, P.V.; Santhi Thilagam, P.
Short message strings are widely prevalent in the age of social networking. Taking Facebook as an example, a user may have many other users in his contact list. However, at any given time frame, the user interacts with only a small subset of these users. In this paper, we propose a recommender system that determines which users have common interests based on the content of the short message strings of different users. The system calculates the similarity between two users based on the contents of short message strings by the users over a certain time period. A similarity measure based on short message strings must be temporal study as the contents of the short messages vary rapidly over time. Experimental study is conducted in the Facebook domain using status updates of users. � 2016 IEEE.
Deriving temporal trends in user preferences through short message strings
(Institute of Electrical and Electronics Engineers Inc., 2016) Deb, S.; Mohan, S.; Venkatraman, P.; Bindu, P.V.; Santhi Thilagam, P.S.
Short message strings are widely prevalent in the age of social networking. Taking Facebook as an example, a user may have many other users in his contact list. However, at any given time frame, the user interacts with only a small subset of these users. In this paper, we propose a recommender system that determines which users have common interests based on the content of the short message strings of different users. The system calculates the similarity between two users based on the contents of short message strings by the users over a certain time period. A similarity measure based on short message strings must be temporal study as the contents of the short messages vary rapidly over time. Experimental study is conducted in the Facebook domain using status updates of users. Â© 2016 IEEE.
Development of CeO2 based High Performance MEMS Oxygen Gas Sensor
(National Institute of Technology Karnataka, Surathkal, 2021) N, Ramshanker.; Mohan, S.; Bhat, M S.
A gas sensor is a device that is used to measure the concentration of gas in its vicinity. It can also be used as a leak detector to detect a gas leak or other emissions. Extensive research is being carried out on gas sensor in designing miniaturized and cost e ective sensors that possess the required characteristics of high sensitivity, selectivity and stability with respect to a speci c application. Fast and unambiguous analysis of human surroundings will be in the near future inseparable part of public health, security and life quality control. Semiconductor metal oxide gas sensors stand out among the other types of sensors because of their simplicity and low cost. In the present work, we developed scalable, high sensitivity, fast response and low operating temperature CeO2 thin lm based oxygen sensors. A systematic investigation has been carried out to develop the high performance oxygen sensor which includes the optimization and integration of sensor lm and micro-heaters. CeO2 thin lms of di erent thicknesses ranging from 90 nm to 340 nm have been deposited at 400oC using RF magnetron sputtering on Al2O3 substrates. Characterization techniques such as Ellipsometry, XRD, XPS and AFM have been used to characterize the CeO2 lms for their thickness, structural, compositional/chemical and surface morphological properties. From XRD and XPS data, it has been observed that all the lms are polycrystalline and with thickness more than 195 nm are stoichiometric. It has also been observed that the resistivity of the lms depends on the texture coe cient of (200) plane of CeO2. It has been found that 260 nm thick lm has high textured coe cient of (200) plane which shows minimum electrical resistivity and maximum sensitivity towards the oxygen gas. The CeO2 lm with an optimum thickness of 260 nm has shown very high sensitivity (12.6), fast response time ( 10 s) and recovery time (15 s) at a low operating temperature of 400oC, which are the best values reported till date in case of undoped CeO2 thin lm based sensors. The response time of CeO2 based sensor may be reduced further by increasing the conductivity of the CeO2 lms with appropriate dopants. v A novel technique was used for the synthesis of CeO2-HfO2 mixed oxide thin lms using RF sputtering. The mixed oxide lms showed better sensing performance in comparison with pure CeO2 lms. The Hf atomic concentration was controlled varying the size and number of HfO2 pellets to achieve the best sensing performance. The CeO2-HfO2 mixed oxide sensor with 10-11% of Hf concentration showed best sensitivity ( 15), response time (8 s) and recovery time (10 s) at a low operating temperature of <400oC reported till date. From XRD and XPS data, it was understood and concluded that the best sensing characteristics of CeO2-HfO2 mixed oxide lm with 10-11% atomic concentration of Hf can be attributed to the existence of a highly reactive plane (200) with the highest surface energy and a strongly reduced surface with oxygen vacancy formation due to the presence of Ce3+ ions and HfOx, x<2 on the surface of the mixed oxide lm. The sensor performance is reproducible without any drift in the base line resistance. Microheaters play a crucial in MEMS gas sensor technology. Several microheater designs have been studied, however new heater patterns and designs are required to achieve excellent temperature uniformity and low power consumption. Here in this work, the area of the heater is optimized in order to increase the resistance by adopting novel designs / geometries. The single meander shape was taken as a reference design. After several modi cations, iterations and optimizations, two di erent geometrical structures namely Perforated Type 1 and Type 2 Platinum microheaters of dimension 500 m x 500 m were designed and analyzed using FEM based software COMSOL. The simulated results show the temperature being distributed uniformly across the entire structure in both the designs. The designed microheaters were fabricated and characterized thermally and electrically and showed excellent temperature uniformity and the power consumed to obtain the temperature of 400oC is nearly between 1.14 to 1.44 W which is considerably lower than reported values in the literature. The fabricated heaters were integrated into a gas sensor and the device was tested for oxygen gas. The sensing results were found to be in good agreement with the results obtained using a conventional heater. Readout circuits are circuits used to convert the sensed signal, such as vi voltage, current, resistance etc. or changes in it into a more convenient form of the same or di erent type of signal for further processing. A highly e cient 3-stage op-amp based readout circuit is designed to measure the dynamic change of the sensing lm resistance. The three stages are namely : constant current source, bu er ampli er and feedback ampli er. The 3 ampli er con guration with a constant current source is used to measure the change in resistance and voltage is measured across the resistance under test. The real-time simulation results show that the circuit is highly e cient and linear.
Development of CeO2-HfO2Mixed Oxide Thin Films for High Performance Oxygen Sensors
(Institute of Electrical and Electronics Engineers Inc., 2021) Ramshanker, N.; Lakshmi Ganapathi, K.L.; Varun, N.; Bhat, M.S.; Mohan, S.
In this work, the authors report the fabrication and characterization of CeO2 -HfO2 mixed oxide thin film based oxygen gas sensors. The atomic concentrations of the individual elements Ce and Hf in the mixed oxide (CeO2 -HfO2) thin films were controlled and tuned using a novel method in RF sputtering to achieve better oxygen sensing characteristics. The characteristics of the sensing film were evaluated using various characterization techniques such as TEM-EDS, FESEM-EDS, XPS and XRD. The XPS and EDS data revealed that the Hf concentration increases with an increase in size as well as number of the HfO2 pellets that are placed on a 3-inch CeO2 target during sputtering. From the XRD and XPS analysis, it was found that the mixed oxide film with 10-11% Hf atomic concentration has the best sensing characteristics. The superior sensing characteristics of the CeO2 -HfO2 film can be attributed to the existence of a highly reactive plane (200) with the highest surface energy and a strongly reduced surface with oxygen vacancy formation due to the presence of Ce3+ ions and HfOx, x < 2 on the surface of the mixed oxide film. The sensor film detected the presence of oxygen gas even at low temperatures (< 400°C); however, the response time and recovery time were slightly higher. The sensor film of thickness 220 nm with Hf concentration between 10-11% showed excellent sensitivity (15), fast response and recovery times of 8 s and 10 s respectively at an operating temperature of 400°C, which are the best values reported till date for CeO2 based oxygen sensors. © 2001-2012 IEEE.
Development of titanium nitride thin film microheaters using laser micromachining
(Elsevier Ltd, 2022) M.a, M.A.; Lakshmi Ganapathi, K.L.; Ambresh, M.; Nukala, P.; Udayashankar, N.K.; Mohan, S.
In this paper, we report the fabrication and characterization of titanium nitride (TiN) thin-film-based microheaters. TiN thin films have been optimized on Si and SiO2 substrates for their optimum electrical resistivities by controlling the process parameters, including argon:nitrogen (Ar:N2) ratio in reactive pulsed DC magnetron sputter (PDCMS) deposition technique. An optical emission spectroscope (OES) was used for monitoring the plasma characteristics at various nitrogen flow rates. The microstructural and surface properties of the TiN films have been investigated and correlated with the electrical properties. It has been observed that the amount of nitrogen flux in the TiN plasma plays an essential role in the microstructural, surface, and electrical properties of the TiN thin films. Micro-heaters have been fabricated with TiN thin films with low electrical resistivity using laser engraving techniques instead of conventional lithographic and micromachining techniques. The TiN microheater has shown excellent performance. A temperature of 406 °C has been achieved by applying an input power of 8 W. This work paves the path for developing scalable and economic TiN microheaters using laser micromachining techniques. © 2021
Novel fabrication technique for NiTi and TiN micro-structures by femtosecond lasers
(IOP Publishing Ltd custserv@iop.org, 2020) M.a, M.A.; Lakshmi Ganapathi, K.L.; Udayashankar, N.K.; Mohan, S.
NiTi shape memory alloy (SMA) thin films were deposited onto silicon substrate using pulsed DC magnetron sputtering technique. To obtain crystalline NiTi thin films has to be synthesized at higher temperatures (475 - 525) C. This high temperature requirement restricts the ease in conventional lithographic procedures. The recent advancements in the laser micromachining lend their applications into the fabrication of miniaturized systems. The femtosecond lasers (FSL) allow non-thermal processing of materials by ablation. This work focuses on the deposition and fabrication of NiTi (â‰ˆ1.5 Î¼m. thick) and titanium nitride (TiN â‰ˆ0.3 Î¼m. thick) thin films based miniaturized systems by femtosecond laser bulk micromachining. The NiTi and TiN microstructures were release by bottom silicon etch using reactive ion etching chlorine chemistry (RIE-Cl). Â© Published under licence by IOP Publishing Ltd.
Photonic crystal ring resonator: A promising device for a multitude applications
(2017) Yadunath, T.R.; Kumar, R.R.; Sreenivasulu, T.; Kandoth, A.; John, K.; Ramakrishnan, R.K.; Das, P.P.; Badrinarayana, T.; Mohan, S.; Hegde, G.; Srinivas, T.
In this paper a 2D Photonic Crystal array in SOI platform having hexagonal periodicity with a ring defect incorporated along with two bus waveguides is conceptualized and realized for various applications of optical communication, sensing etc. The ring structure filters out a resonant wavelength from the spectrum carried to it through the line defect where the resonated peak is determined by the effective ring radius. The hexagonal architecture enables more coupling length than an ideal ring structure which helps in better intensity accumulation. The resonant peak exhibited at 1554nm in simulation, which is observed in the optical characterization at 1543nm. This is attributed to the fabrication tolerance. � 2017 SPIE.
Photonic crystal ring resonator: A promising device for a multitude applications
(SPIE spie@spie.org, 2017) Yadunath, T.R.; Kumar, R.R.; Tupakula, T.; Kandoth, A.; John, K.; Ramakrishnan, R.K.; Das, P.P.; Badrinarayana, T.; Mohan, S.; Hegde, G.M.; Srinivas, T.
In this paper a 2D Photonic Crystal array in SOI platform having hexagonal periodicity with a ring defect incorporated along with two bus waveguides is conceptualized and realized for various applications of optical communication, sensing etc. The ring structure filters out a resonant wavelength from the spectrum carried to it through the line defect where the resonated peak is determined by the effective ring radius. The hexagonal architecture enables more coupling length than an ideal ring structure which helps in better intensity accumulation. The resonant peak exhibited at 1554nm in simulation, which is observed in the optical characterization at 1543nm. This is attributed to the fabrication tolerance. Â© 2017 SPIE.
Physical model studies on the stability of emerged seaside perforated semicircular breakwaters
(National Institute of Science Communication and Policy Research, 2018) Hegde, A.V.; Mohan, S.; Pinho, J.L.S.; Sharhabeel, P.S.
Present study discusses experiments conducted in a two dimensional monochromatic wave flume to determine the critical (minimum) weight required to resist the sliding of an emerged seaside perforated semicircular breakwater model. It is observed from a detailed review that there is hardly any literature, stressing the critical weight determination for the sliding stability of this breakwater type. Hence, the present research was taken up to study the variations in the critical weight required for sliding stability with different wave and structural specific parameters. The variations were recorded graphically using non-dimensional parameters obtained from a dimensional analysis using Buckingham’s ? theorem. © 2018, National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved.
Pulsed DC magnetron sputtered titanium nitride thin films for localized heating applications in MEMS devices
(Elsevier B.V., 2018) M.a, M.A.; Lakshmi Ganapathi, L.G.; G N V R, V.; Udayashankar, N.K.; Mohan, S.
Titanium nitride (TiN) thin films are deposited on Si/SiO2 substratesby using Pulsed DC magnetron sputtering and are characterized for their structural, mechanical and electrical properties for their application as localized heating elements in microsystem devices. The influence of substrate temperature on the properties of TiN films has been investigated. The correlation between the structural orientation with mechanical and electrical properties has been established. The films deposited at a substrate temperature of 300 °C have shown better structural, mechanical and electrical properties. This film has been chosen for the fabrication of microheater and its characterization. A maximum temperature of 250 °C is achieved by applying a power of 2.8 W to the microheater. © 2018 Elsevier B.V.
RF Sputtered CeO2 Thin Films-Based Oxygen Sensors
(Institute of Electrical and Electronics Engineers Inc., 2019) Ramshanker, N.; Lakshmi Ganapathi, K.L.; Bhat, M.S.; Mohan, S.
In this paper, we report the scalable, high sensitivity, fast response, and low operating temperature Cerium oxide (CeO2) thin film-based oxygen sensors by optimizing CeO2 film thickness. CeO2 thin films of thickness ranging from 90 to 340 nm have been deposited at 400°C using radio frequency (RF) magnetron sputtering on Al2O3 substrates. Ellipsometry, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) have been used to characterize the CeO2 films for their thickness, structural, compositional/chemical, and surface morphology properties. Gas sensors have been fabricated using CeO2 film as a sensing material and tested in an oxygen gas environment. CeO2 film with an optimum thickness of 260 nm has shown high sensitivity (12.6) and fast response time (?10 s) along with fast recovery time (15 s) at a low operating temperature of 400°C. To the best of our knowledge, these are the best values reported till date for undoped CeO2 thin film-based oxygen sensors. Furthermore, from the sensor's response, it was observed that there was no drifting from the baseline. This superior performance of CeO2 thin film-based oxygen sensor may be attributed to the combination of three factors, i.e., 1) high surface energy and reactivity due to the presence of (200) oriented CeO2 plane; 2) low resistance due to better crystallinity; and 3) perfect stoichiometry with required roughness. © 2001-2012 IEEE.