Indian Institute of Technology Dharwad
Recent publications
Oxide‐Metal‐Oxide (OMO) based stacks are highly attractive by virtue of their favorable properties for being used as a top transparent electrode (TE) in semi‐transparent solar cells (ST‐SCs). This work focused on getting the best trade‐off between performance and transparency by optimizing the OMO electrode and the device layers with the help of optical simulation. We investigated NiO/Ag/SnO2 as the OMO electrode integrated into a device having SnO2, Spiro‐OMeTAD, and MAPbI3 as the electron transport layer (ETL), hole transport layer (HTL), and photoactive layer, respectively in n‐i‐p geometry. We have shown that an optimized OMO electrode in terms of average visible transparency (AVT) does not translate to the best device performance. We found that for the overcoat to undercoat oxide layer ratio of 1.17 a maximum JSC of 4.34 mAcm‐2 is achieved while a maximum AVT of 21.55% is obtained for a ratio of 0.78. On further optimization of the MAPbI3 thickness, for an oxide ratio of 1, a modeled device with 4.58 mAcm‐2 with AVT of 31.55% is demonstrated. In addition, it is also found that by integrating an optical spacer layer after the OMO electrode, the JSC of the device shows a jump of >115% to 9.86 mA/cm2. This article is protected by copyright. All rights reserved.
An (m,n)-colored mixed graph, or simply, an (m,n)-graph is a graph having m different types of arcs and n different types of edges. A homomorphism of an (m,n)-graph G to another (m,n)-graph H is a vertex mapping that preserves adjacency; and the type and direction of the adjacency. An (m,n)-relative clique of G is a vertex subset R whose images are always distinct under any homomorphism of G to any H. The maximum cardinality of an (m,n)-relative clique of a graph is called the (m,n)-relative clique number of the graph. In this article, we explore the (m,n)-relative clique numbers for three different families of graphs, namely, graphs having bounded maximum degree Δ, subcubic graphs, partial 2-trees and planar graphs and provide tight or close bounds in most cases.
This paper presents a dead-band compensated multiband stacked electromagnetic energy harvester for powering sensor nodes. It is adaptive for typical ambient RF power levels found within the environment. A stage-stage feedforward technique is adopted in the proposed harvester to enhance the output voltage, in turn, harvested power and sensitivity. Moreover, a compensation circuit is included in the design for bypassing the inactive bands to avoid unexcited band rectifier diodes. A prototype is designed to cover four frequency bands GSM (900 MHz, 1800 MHz), 4G-LTE (2.3 GHz), and Wi-Fi (2.4 GHz) and further integrated with TI BQ25570 power converter. The analytical, simulated, and measured results show the increment in the output voltage with the frequency bands. The measured efficiency of the RF-DC converter is 44.2% at -20 dBm input power and 89% at 0 dBm. The efficiency is improved by 13% on average under dead-band compensation. With the multiband stacking, the harvester achieves a start-up voltage of 320 mV at -24 dBm and found to be efficient to drive a temperature sensor STLM20 at -12 dBm input power.
Abnormal protein kinetics could be a cause of several diseases associated with essential life processes. An accurate understanding of protein dynamics and turnover is essential for developing diagnostic or therapeutic tools to monitor these changes. Raman Spectroscopy in combination with stable isotope probes such as carbon‐13, and deuterium has been a breakthrough in the qualitative and quantitative study of various metabolites. In this work, we are reporting the utility of Raman stable isotope probing (Raman‐SIP) for monitoring dynamic changes in the proteome at the community level. We have used 13C‐ labelled glucose as the only carbon source in the medium and verified its incorporation in the microbial biomass in a time‐dependent manner. A visible redshift in the Raman spectral vibrations of major biomolecules such as nucleic acids, phenylalanine, tyrosine, amide I and amide III were observed. Temporal changes in the intensity of these bands demonstrating the feasibility of protein turnover monitoring were also verified. Kanamycin, a protein synthesis inhibitor was used to assess the feasibility of identifying effects on protein turnover in the cells. Successful application of this work can provide an alternate/adjunct tool for monitoring proteome level changes in an objective and non‐destructive manner.
We find Evolutionary Stable Strategy (ESS) and Evolutionary Stable Preference (ESP) in conflict modeled as a pairwise contest game for an endogenous prize. Our study attributes overbidding under ESS to misperceptions about various attributes of rival players in a conflict that evolved through ESP. We show that players tend to over perceive the resource endowments of rival players and this, in turn, gives rise to the more aggressive behaviour of players under ESS. We also use the notion of conflict expenditure in an endogenous prize setting to show that the false perception about the rival players under ESP gives rise to higher levels of dissipation of resources into appropriation. JEL Classifications: D70, D72, D74
A green-based approach for the synthesis of silver nanoparticles has gained tremendous attention in biomedical applications. Fungal endophytes have been recognized as a remarkable biological source for the synthesis of potential nanodrugs. The present study focuses on the fabrication of silver nanoparticles using the fungal endophyte Penicillium oxalicum (POAgNPs) associated with the leaf of the Amoora rohituka plant. Sharp UV−visible spectra at 420 nm appeared due to the surface plasmon resonance of POAgNPs and the reduction of silver salt. FT-IR analysis revealed the presence of functional groups of bioactive compounds of P. oxalicum responsible for the reduction of silver salt and validated the synthesis of POAgNPs. A high degree of crystallinity was revealed through XRD analysis, and microscopy-based characterizations such as AFM, TEM, and FESEM showed uniformly distributed, and spherically shaped nanoparticles. Furthermore, POAgNPs showed a potential inhibitory effect against bacterial and fungal strains of pathogenic nature. POAgNPs also exhibited potential antioxidant activity against the synthetically generated free radicals such as DPPH, superoxide, hydroxyl, and nitric oxide with EC 50 values of 9.034 ± 0.449, 56.378 ± 1.137, 34.094 ± 1.944, and 61.219 ± 0.69 μg/mL, respectively. Moreover, POAgNPs exhibited cytotoxic potential against the breast cancer cell lines, MDA-MB-231 and MCF-7 with IC 50 values of 20.080 ± 0.761 and 40.038 ± 1.022 μg/mL, respectively. POAgNPs showed anticancer potential through inhibition of wound closure and by altering the nuclear morphology of MDA-MB-231 and MCF-7 cells. Further anticancer activity revealed that POAgNPs induced apoptosis in MDA-MB-231 and MCF-7 cells by differential expression of genes related to apoptosis, tumor suppression, and cell cycle arrest and increased the level of Caspase-3. The novel study showed that P. oxalicum-mediated silver nanoparticles exhibit potential biological activity, which can be exploited as nanodrugs in clinical applications.
Higher energy requirement for asphaltic layer construction with asphalt binder containing reactive elastomeric terpolymer (RET) and poly phosphoric acid (PPA) can be addressed to a greater extent with the addition of warm mix asphalt (WMA) additives. However, moisture damage related problem is one of the concerns with such addition, which further aggravates with an increase in ageing level. The addition of lime may help in addressing moisture damage related problems in such cases. Previous research works show that based on the interaction between asphalt binder and particular WMA additive, the viscosity may undesirably increase also. So far, the influence of different WMA additives (wax, chemical surfactant (CS) and water-based (WB)) on the workability related properties of asphalt binder containing RET and PPA is not understood. It is also not clear if such warm mix additives with/without lime can help in improving long-term bonding with different aggregate types or not. Therefore, this research work aimed at identifying the appropriate WMA additive (with/without lime) which can help in (a) addressing the workability related problem and (b) improving long-term bonding with different aggregate types. To achieve this, different types of WMA additives (with/without lime) were added to RET and PPA modified binder. Viscosity-based measurement and chemical analysis using Fourier transform infrared spectroscopy were performed to understand workability and underlying chemical changes. Results indicated that although wax and CS-based warm mix additives can help in reducing energy demand, the addition of WB warm mix additive will have a negative impact from the workability perspective. Likewise, dynamic contact angle for different binder combinations was measured to evaluate the surface free energy components, which further helped to examine the long-term bonding with different aggregate types. Among different WMA additive types, the use of wax-based WMA additive was found to be most effective in improving compatibility with different aggregate types. Also, irrespective of the binder combination, the addition of lime improved the long-term bonding with considered aggregate types.
DC microgrids are increasingly gaining attention in industrial applications due to their simpler and more efficient integration with renewable energy resources and energy storage elements. The DC grid demands a faster, compact, cost-effective, and fault-tolerant protective system for reliable operation. To address the above challenges, this paper proposes a bidirectional solid-state dc circuit breaker topology that guarantees the reliable operation of dc grids (LVDC and MVDC). A modular extension of the proposed circuit breaker is also presented, resulting in better reliability, scalability, and fault-tolerant operation. The circuit breaker is derived using power semiconductor devices (SCRs and IGBTs), with SCR acting as a main power interruption device. Salient features of the proposed topology include modularity, use of low-power rated devices, low-current rated sensors, and pre-fault interruption. A detailed mathematical analysis validating the design and operation of the proposed modular circuit breaker is presented. Moreover, the paper also highlights the merits and limitations of the proposed concept. Finally, a laboratory prototype is developed with a system specification of 400VDC/14A to validate the performance of the proposed circuit breaker with single and modular operations, which is in line with the obtained simulation results. To verify current sharing between the modules, a few non-ideal conditions such as the use of non-identical main SCRs, and turn-on delay are considered and tested on the developed prototype.
In the race for feeding the growing population and making a commercial profit, food that is our daily need is manipulated and adulterated in many ways. Food forgery is real, and it can cause a concerning impact on the health of an individual. Food forgery includes adulteration, tampering with the colour, flavour, the texture of food, tampering and mislabelling food packages, shortcuts in the farming and manufacturing process, excessive use of growth hormone, or pesticide, usage of substandard ingredients, and many more. Conventional methods for monitoring the quality of food are diligent, invasive, and time taking processes. Bio-photonics spectroscopic techniques such as infrared spectroscopy, fluorescence spectroscopy, Raman spectroscopy, and imaging technology combined with computational power give a reliable, non-destructive, portable, non-invasive way to do online quality monitoring and shelf-life prediction of the food. Bio-photonics is the interdisciplinary field of science that studies the interaction of light with biological matters. Studying the emission, absorption, and scattering phenomenon of light when it interacts with the food can give us different aspects of food quantity and quality. These techniques have the potential to detect pathogens, contamination, and protein and lipid structural changes in food at the molecular level. This review article aims to summarize the different spectroscopic techniques and their challenges in analysing and monitoring the different aspects of food quality.
This paper proposes a single axis, high performance CMOS-MEMS closed-loop accelerometer, implemented using In-Plane movable Suspended Gate Field Effect Transistor (IP-SGFET). The IP-SGFETs gate is embedded within a movable proof mass supported by flexible folded beams. The external acceleration displaces the proof-mass, which changes the drain current of IP-SGFET. The change in current is read out with the help of a simple differential amplifier which is constructed with the IP-SGFET. The differential amplifiers output voltage is used through a closed-loop integral control and a high voltage dynamically reconfigurable charge pump, that generates a high voltage differential drive of up to 10.5±5.12 V, to drive an actuator that brings the gate back to its resting position. The actuator used is a comb-drive type electromechanical actuator. In this work, two tools, viz. MEMS+ and TCAD device simulation tools are used in a sequential manner to handle the electrostatics coupled with the micro-mechanical domain present in the SGFET. The results obtained are then used as Look-up-tables for the design and simulation of the entire system, including the control circuits, in SPECTRE. Appropriate design of the MEMS suspended structure, the FET device and interface circuit results in a open loop sensitivity of 927 mV/g with a near-zero cross-axis sensitivity. Using the actuator and the reconfigurable charge pump, closed loop operation is realized with a dynamic range of ±4 g at a supply voltage of 3.3 V.
Crops emit volatile organic compounds (VOCs) when infested with diseases or pests as a natural self-defense mechanism. These VOCs can effectively indicate the biotic stresses of crops and, hence, can be termed as biomarkers of crop stress. This study reports the development of cupric oxide (CuO) nanoflake-based resistive sensors for the detection of linalool, methyl salicylate, and hexanal, which indicate biotic stresses in multiple crops, including maize. CuO nanoflakes were synthesized using a hydrothermal method. Their lateral dimensions were found to be ∼300 nm, and the thickness was ∼28 nm when studied using a field emission scanning electron microscope. The band gap of the semiconducting material was ascertained to be 1.82 eV through UV−visible spectroscopy. The CuO sensors were tested at different temperatures and were found to exhibit the highest response to all the target vapors at 250 °C. The sensors were tested at different concentrations (25−200 ppm) of the three VOCs. The response of the CuO sensor was found to be the highest for linalool and ranged from 6.7 to 13.3 times. The response was found to be 4.7− 12.2 times for methyl salicylate and 1.2−2.7 times for hexanal at 250 °C. As selectivity is an important parameter of any sensor, a novel technique with a simple algorithm considering the response of the CuO nanoflakes at two different temperatures (250 and 300°C) was developed to improve the selectivity and the prediction accuracy of the sensors.
Research on intelligent wireless network aims at the development of a human society which is ubiquitous and mobile, simultaneously providing solutions to the coverage, capacity, and computing issues. These networks will focus on provisioning intelligent use-cases through higher data-rates over the millimeter waves and the Tera-Hertz frequency. However, at such high frequencies, multiple non-desired phenomena such as, atmospheric absorption and blocking occur which create a bottleneck owing to resource scarcity. Hence, existing trend of exactly reproducing transmitted data at the receiver will result in a constant need for higher bandwidth. A possible solution to such a challenge lies in semantic communications which focuses on meaning (relevance or context) of the received data. This article presents a detailed survey on the recent technological trends in regard to semantic communications for intelligent wireless networks. Initially, the article focuses on the semantic communications architecture including the model, and source and channel coding. Next, cross-layer interaction, and various goal-oriented communication applications are detailed. Further, overall semantic communications trends are presented following which, the key challenges and issues are detailed. Lastly, this survey article is an attempt to significantly contribute towards initiating future research.
Global electricity generation by renewable energy sources and electrification of the transportation system are gaining more importance to mitigate climate change. The dc system has been playing a significant role in these developments. To protect dc systems, dc circuit breakers with advanced technology are required that are fast and reliable. Various solid-state dc circuit breakers such as Z-source and T-source circuit breakers have been presented in the literature to meet the dc system demand, however, these topologies suffer from limitations such as high conduction loss, complexity in design, no physical isolation, and presence of negative current flow in load during reclosing. To overcome the above said limitations, a bidirectional solid-state dc circuit breaker (BD-SSCB) has been proposed in this paper that detects the overload or short circuit faults and responds instantaneously to mitigate the fault current. The controllable shutoff function is much needed in applications where sudden load change occurs continuously during the normal operation, such as varying acceleration of an electric vehicle. The proposed BD-SSCB is validated using spice simulations and hardware experiments with varying system parameters for a system rating of 400V/10A.
Mechanical properties and fracture morphologies of Poly-Lactic acid (PLA) neat and composites (PLA reinforced with Aluminium, Copper, Carbon fibres and Brass) developed by Material Extrusion based Additive Manufacturing technique were studied to consolidate the comprehensive data for various applications. In the current study, printing parameters viz., layer height, print angle and print speed were varied to form the arrays of experimental trials to estimate the Tensile (Ultimate Tensile strength, young's moduli) and Flexural (Maximum bending strength) properties. Further, the study emphasized on fracture morphologies and categorized the types of fractures within the PLA neat and composite samples via Field Emission Scanning Electron Microscope (FESEM). An analytical model was adopted for a qualitative validation of results of micrographs for estimating the tensile and bending strengths. Results showed that the percentage improvement in the young's modulus was relatively higher for carbon fibre and brass reinforced composites in comparison to the other counterparts. It was conclusive from fracture morphology that the Intra-laminar type of fracture was prominent. However, PLA + Carbon Fibre (CF) samples exhibited Trans-laminar type of fracture, owing to their higher aspect ratio. Also, the composite samples exhibited better strengths during flexural test, in comparison to the tensile test. Optimization plots showed that the print angle was the most dominant factor influencing the strength values.
High-temperature reverse bias (HTRB) stress effects on static and dynamic characteristics of 0.15 $\mu$ m AlGaN/GaN high-electron mobility transistors (HEMTs) are reported. The HEMTs were stressed to off-state bias ( $V_{\mathrm{GS}} $ $=$ $-$ 7 V and $V_{\mathrm{DS}} $ $=$ 30 V) at a high temperature of 175 $^{\circ}$ C for 1000 h of duration. The HTRB-induced changes in drain current ( $I_{\mathrm{DS}})$ are analyzed. The $I_{G}$ – $V_{G}$ characteristics are evaluated at $V_{\mathrm{DS}} $ $=$ 0 V (emulating gate Schottky diode leakage) before and after the stress to examine the Schottky gate diode properties upon aging. The gate leakage current variations are further inspected with $V_{G}$ and $V_{D}$ sweeps. After aging test, a considerable drift in the output power ( $P_{\mathrm{out}})$ is observed during the interim RF measurement of the stressed HEMTs. The pulsed $I_{\mathrm{DS}}$ – $V_{\mathrm{DS}}$ characteristics reveal the reduction in $I_{\mathrm{DS}}$ , particularly in the transition between linear and saturation regions; which is referred as knee-voltage smoothing. The output-admittance ( $Y_{22})$ and drain current transient (DCT) measurements are conducted to track any new defects created in the stressed HEMT and also assess the evolution of the pre-existing trap parameters. Especially, the physical location of the traps responsible for the knee-voltage smoothing and output power drift is identified by TCAD simulations.
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338 members
Surya Singh
  • Department of Biosciences and Bioengineering
Rahul Pandya
  • Department of Electrical Engineering
Sudheer Siddapureddy
  • Department of Mechanical Engineering
Banavath Satish Naik
  • Department of Electrical Engineering
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