Department of Electrical Engineering

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IIT Jodhpur

Tin Oxide (SnO2) has established itself as excellent receptor in chemiresistive detection of ammonia gas in last two decades. There have been several routes developed to obtain a pristine SnO2 film over this time however, physical vapor deposition remains an attractive route for the same due to the control it provides for the growth and its scalability for industry scale production. In this work, we report on the effect of oxygen and argon ratio at different pressure in sputtering unit on the sensitivity of tin oxide. In particular, our investigation revealed that the device based on SnO2 thin film obtained at an sputtering pressure of 10 mTorr and Ar/O2 ratio of 50/50 possess highest response (~27.97% for 30 ppm of ammonia) at optimal temperature of 220 ℃. © 2020 Elsevier B.V.

World University root node

Materials Letters

Assessing simultaneous effect of Ar/O2 ratio and process pressure on ammonia sensing properties of reactive DC magnetron sputtered SnO2 thin films

Reconfigurable intelligent surface (RIS) is an emerging technology that can achieve reconfigurable radio propagation environments for beyond 5G/6G wireless systems by smartly tuning the signal reflection via a large number of low-cost passive reflecting elements. In this letter, we investigate the effect of co-channel interference (CCI) on RIS-based dual-hop mixed free-space optical (FSO)-radio frequency (RF) communication systems. The source node, equipped with multiple FSO apertures, transmits subcarrier intensity modulated symbols on the FSO link subjected to Gamma-Gamma (GG) distributed atmospheric turbulence with pointing errors (PEs). It is assumed that the relay-RIS and RIS-destination links follow Rayleigh distribution. The destination node is corrupted by multiple CCI (each following Rayleigh distribution). The performance of the considered system is evaluated by deriving novel closed-form expressions for the outage probability (OP) and bit error rate (BER). It is shown through numerical results that RIS-based dual-hop mixed FSO-RF system provide a significant performance enhancement in comparison to a traditional dual-hop mixed FSO-RF system even in presence of CCI. © 1997-2012 IEEE.

IEEE Communications Letters

Reconfigurable Intelligent Surface for Mixed FSO-RF Systems with Co-Channel Interference

Free space optical (FSO) communication is a promising candidate for the next generation (5G and beyond) wireless communication systems, due to its merits (i.e. low latency, high data rate, and license-free band, among others). However, atmospheric turbulence (AT) as well as pointing error (PE) are two of the main challenges with FSO communication that affect its performance. Here, the exact closed-form expression of the average secrecy capacity and secrecy outage probability under the composite effect of AT and non-zero boresight PEs is evaluated. For all the regimes of the AT (weak to strong), a generalised Malaga distribution is used to model the channel fading gain of the FSO link. The expressions are generalised and valid for all turbulence, and are applicable for intensity modulation direct detection as well as heterodyne detection techniques. © 2020 The Authors. IET Communications published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology

Fulltext

IET Communications

Secrecy performance of FSO communication systems with non-zero boresight pointing errors

The perturb & observe (P&O) algorithm is very popular for maximum power point tracking (MPPT) for solar photovoltaic (PV) systems. However, it has tracking problems during varying irradiations as well as the nuisance of oscillations around the maximum power point (MPP). This work introduces a circle center-line concept based P&O (CCCP&O) algorithm for MPPT, where, the concept of circle and its center are combined with the PO algorithm. This algorithm tends to reduce the number of iterations taken to reach the MPP, which reduces settling time. Moreover, the problem of large oscillations around the MPP is eliminated by using the concept of flexible step size. The algorithm initializes with standard PO, but utilizes a approach of diameter equivalence of a circle as a procedure to reach next operating point on the power-voltage plot. Therefore, the iterations required to get to the MPP are reduced substantially. The MPP changes with change in solar irradiance, therefore, a concept of artificial envelope around the P-V curve is used to improve tracking of the algorithm during varying irradiances. The overall performance of the algorithm is demonstrated and compared in simulation using SIMULINK MATLAB as well as also shown experimentally in a developed hardware prototype. © 2004-2012 IEEE.

IEEE Transactions on Circuits and Systems I: Regular Papers

A Rapid Circle Centre-Line Concept-Based MPPT Algorithm for Solar Photovoltaic Energy Conversion Systems

The Mach number, angle of attack and altitude of operation for an interceptor vary widely during the course of its trajectory. As a result, the interceptor Center of Pressure (CP) locations move significantly around a given Center of Gravity (CG) location at these operating conditions. This results in an inevitable variation in aerodynamic static stability leading to stable and unstable operating regions. In order to ensure good speed of response during the interceptor homing phase, lesser static stability is desirable. Hence the requirement to handle aerodynamic instability at some other operating conditions in the interceptor envelope become inevitable. Since flexibility has a strong bearing on autopilot design, it becomes necessary to control unstable operating points in the presence of flexibility modes. Despite the static stability variation, aerodynamic design can control the level of maximum instability of the configuration. Hence the maximum static instability the autopilot can handle has to be specified for aerodynamic configuration design. This paper brings out the limitations of autopilot design in controlling an unstable interceptor with low bending mode frequencies in terms of maximum instability the autopilot design can handle, which serves as an important input for aerodynamic design. © 2021 The Franklin Institute

Journal of the Franklin Institute

Limitations of autopilot design for controlling a statically unstable flexible interceptor

The AC loads cause the DC bus voltage and the source current to oscillate at twice the AC supply frequency (fac). These oscillations have detrimental effects on sources and converter components. A distributed control strategy is proposed to regulate the current ripples propagating to the sources, in a DC microgrid feeding both the AC and DC loads. The proposed control methodology regulates the output impedance of the source interfacing DC-DC converter dynamically at 2fac. The impedance is increased virtually in series with the inductor of the DC-DC converter by a dedicated controller, which regulates the ripple magnitude according to the harmonic reference. Using this, the second-order ripple currents can be mitigated or propagated to the nodes having some ripple absorbing circuits, or filters. This improves energy density in ripple filters installed at a node and optimal usage of the DC link capacitor at node terminals is achieved. The proposed SRC regulation is analyzed in presence of component variations and communication delay between the nodes. A low bandwidth communication is incorporated so as to facilitate the per-unit current exchange between the nodes for the proportional DC load sharing. The proposed concept is verified through simulation and experimentation. IEEE

IEEE Journal of Emerging and Selected Topics in Power Electronics

Dynamic Virtual Impedance based Second Order Ripple Regulation in DC Microgrids

The human musculoskeletal (MSK) system (also known as the locomotor system) provides strength and assistance to perform functional tasks and daily life activities. The MSK health monitoring plays a vital role in maintaining the body mobility and quality of life. Manual approaches for musculoskeletal health monitoring are subjective and require a clinician's intervention. The evolution in motion tracking technology enables us to capture the fine details of body movements. The research community has proposed various approaches to help clinicians in diagnosis and monitor treatment sessions. This paper succinctly reviews the evolution of technology-assisted approaches for musculoskeletal health monitoring, using motion capture sensors. To streamline the search through the literature database, the PICOS framework and PRISMA method have been incorporated. The present study reviews methods to transform motion capture data into kinematics variables and factors that affect the tracking performance of RGB-D sensors. Furthermore, widely utilized time-series filters for skeletal data denoising and smoothing for kinematics analysis, stochastic models for movement modeling, rule-based and template-based approaches for rehabilitation exercises assessment, and telerehabilitation sessions for remote health monitoring are explored. This article analyzes skeletal tracking methods by providing advantages and drawbacks of the state of the art rehabilitation sessions assessment, skeletal joint kinematics analysis, and MSK Telerehabilitation approaches. It also discusses the possible future research avenues to improve musculoskeletal disorder diagnosis and treatment monitoring. Our review signifies that RGB-D sensor-based approaches are inexpensive and portable for disorder diagnosis and treatment monitoring. It can also be a viable option for clinicians to provide contactless healthcare access to patients in the current scenario of the COVID-19 pandemic. © 2021 Elsevier Ltd

Computers in Biology and Medicine

A review of the evolution of scientific literature on technology-assisted approaches using RGB-D sensors for musculoskeletal health monitoring

The crucial role of molecular weight of the polymer dielectric in regulating the electrical performance and photo-response of TIPS-pentacene OFETs has been explored using poly(vinyl alcohol) (PVA) as the polymer dielectric layer. With increasing molecular weight of PVA, a degradation in the electrical and photo-response was observed. Atomic-force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR) and X-ray Diffraction (XRD) studies revealed that with increase in PVA molecular weight, polarizability of PVA dielectric layer and thus strength of the OFET channel reduced due to decreased hydroxyl group concentration oriented perpendicular to the PVA-semiconductor interface. Further, due to rising surface roughness of underlying PVA film with its molecular weight, macroscopic irregularities and therefore trap density in the active layer grown over it also increases. Therefore, both of these molecular weight dependent factors influence overall device performance and photo-response of OFETs in a critical way. © 2021 Elsevier Ltd

Polymer

Influence of molecular weight of polymer dielectric on the photo-response of solution-processed OFETs

A novel design technique of planar triple band self-triplexing Substrate Integrated Waveguide (SIW) cavity backed slot antenna is presented. The proposed antenna uses three separate feeding ports to excite three SIW cavity modes into the proposed design. A dumbbell shaped slot antenna placed at top metallic plate is excited by these modes to radiate at corresponding resonant frequencies in C (4-8 GHz), X (8-12 GHz) and Ku (12-18 GHz) band. The behaviour of the proposed SIW cavity modes are analyzed with the help of half mode theory to predict the resonant frequencies of the proposed antenna. The fabricated prototype of the antenna resonates at 6.76 GHz, 8.62 GHz and 13.33 GHz and exhibits unidirectional radiation pattern with a gain of 3.78 dBi, 4.46 dBi, 5.6 dBi and front-to-back ratio (FTBR) of 14 dB at three resonant frequencies respectively. The proposed antenna maintains a high isolation of better than 15 dB between its three excitation ports while retaining its compact configuration which makes it attractive for high frequency on chip antenna applications. © 2021 EurAAP.

15th European Conference on Antennas and Propagation, EuCAP 2021

Design of Compact SIW Cavity Backed Self-triplexing Planar Slot Antenna for Triple Band Application

The possibility to synergise two-dimensional (2D) materials with 0D nanoparticles has sparked a surge in high performance futuristic electronic devices. Here, we decorated plasmonic Au nanoparticles on surface of chemical vapor deposition (CVD) grown 2D MoS2 nanosheet and demonstrated bifunctional sensing behaviour within a single device. The plasmonic Au nanoparticles functionalized MoS2 device showed about 5 times higher sensitivity to NO2 than that of pristine MoS2 at room temperature. The enhanced gas sensing performance was attributed to a combination of Schottky barriers modulation at Au/MoS2 nanointerfaces and catalytic effects upon exposing the gas analyte. In addition, the device also exhibited enhanced photoresponse with a high photo-responsivity of 17.6 A/W and a moderate detectivity of 6.6 × 1011 Jones due to enhanced local plasmonic effects. Finally, photons and gas molecules are detected in sequence, which proved that only a single Au-MoS2 device exhibited remarkable bifunctional sensing characteristics. Such excellent bifunctional sensing ability of a single Au-MoS2 device paves the way to integrate the 2D material with plasmonic nanostructures for developing an advanced multifunctional sensor. © 2001-2012 IEEE.