Indian Institute of Technology Palakkad
Recent publications
In this research, a very interesting and little-discussed contact of a thin shell with a rigid substrate is studied. The standard problem considered is that of a cylindrical shell, which is subjected to a uniform line load on top, resting on a smooth planar rigid substrate. The material is assumed to be linearly elastic. To solve the contact problem, the available shell theories have been used, the governing equilibrium equations are solved separately for contact and free regions and then the continuity conditions of displacements and stresses at the intersection of the two regions have been used. Out of all the shell theories available, the linear Cosserat shell theory, shear deformation theory, and the Flügge-Lur’e-Byrne shell theory have been selected. The results are obtained for the radial and tangential displacements, contact pressure, and also for the applied load vs contact patch length plots. The results obtained from the Cosserat, shear deformation, and Flügge-Lur’e-Byrne shell theories are compared with those from finite element simulation (using ABAQUS). It has been observed that for thin shells (that is for thickness to radius ratio less than 0.1) the contact pressure and load vs contact length results obtained from the Cosserat theory and FE simulation are in excellent agreement. In contrast, the contact pressure obtained from shear deformation and Flügge-Lur’e-Byrne theories has a non-zero value at the edge of the contact region that is there is a discontinuity in contact pressure at the contact edge. Also, the limitations of Flügge-Lur’e-Byrne theory to accurately predict the load vs contact patch length behavior have been highlighted. Therefore, it has been concluded that the inclusion of transverse shear strains along with transverse normal stress and strain is necessary in order to accurately capture the physics of the contact problems of shell-like structures and Cosserat theory provides the best analysis for such complex problems.
Metal additive manufacturing (MAM) process has gained enormous popularity in the past few decades due to its capability to fabricate the components in near-net-shape with minimal material wastage. Owing to its flexibility to produce complex/intricate shapes, the process has found several applications in the aerospace, automobile and biomedical industries. However, wide industrial acceptance of the MAM components is lagging because of their poor dimensional accuracy and surface integrity which limits the functionality and achievable tolerances when compared to the subtractive manufacturing methods. Thus, a post-processing strategy is needed to enhance the dimensional accuracy and surface integrity of the additive manufactured components. Manual inspection of various features, especially corner profiles, can be expensive, time-consuming and inaccurate. Ti6Al4V alloy has wide applications in aerospace, biomedical and marine industries due to its superior properties like strength-to-weight ratio, biocompatibility and fatigue resistance. This article presents an image-processing approach for improving the corner accuracy and surface integrity of selective laser-melted (SLM) Ti6Al4V components using wire electric discharge polishing (WEDP). Subsequently, fourteen components with different corner profiles, namely acute (θ = 30O), orthogonal (θ = 90O) and obtuse (θ = 120O), were fabricated by varying laser power, hatch distance and scan speed. Minimum polishing depth has been evaluated by capturing the raw images of MAM components, and the corner profiles are extracted using an image-processing approach. A significant improvement in dimensional accuracy of 80.7%, 77.3% and 85.4% was obtained for orthogonal, acute and obtuse profiles respectively after WEDP. Moreover, the surface roughness (Sz) reduction from ~ 61.86 to ~ 8.41 μm was achieved along with removing micro-pits and voids, waviness and balling defects from the surface. EDS analysis showed that only a negligible amount of Zn (0.57 wt. %) and Cu (0.8 wt. %) is present over the finished surface. Based on the above findings, WEDP showed excellent capabilities in conjunction with an image-processing approach to enhance the dimensional accuracy and surface integrity of metal additive manufactured components.
Grasslands are the largest contributor of nitrous oxide (N 2 O) emissions in the agriculture sector due to livestock excreta and nitrogen fertilizers applied to the soil. Nitrification inhibitors (NIs) added to N input have reduced N 2 O emissions, but can show a range of efficiencies depending on climate, soil, and management conditions. A meta-analysis study was conducted to investigate the factors that influence the efficiency of NIs added to fertilizer and excreta in reducing N 2 O emissions, focused on grazing systems. Data from peer-reviewed studies comprising 2164 N 2 O emission factors (EFs) of N inputs with and without NIs addition were compared. The N 2 O EFs varied according to N source (0.0001–8.25%). Overall, NIs reduced the N 2 O EF from N addition by 56.6% (51.1–61.5%), with no difference between NI types (Dicyandiamide—DCD; 3,4-Dimethylpyrazole phosphate—DMPP; and Nitrapyrin) or N source (urine, dung, slurry, and fertilizer). The NIs were more efficient in situations of high N 2 O emissions compared with low; the reduction was 66.0% when EF > 1.5% of N applied compared with 51.9% when EF ≤ 0.5%. DCD was more efficient when applied at rates > 10 kg ha ⁻¹ . NIs were less efficient in urine with lower N content (≤ 7 g kg ⁻¹ ). NI efficiency was negatively correlated with soil bulk density, and positively correlated with soil moisture and temperature. Better understanding and management of NIs can optimize N 2 O mitigation in grazing systems, e.g., by mapping N 2 O risk and applying NI at variable rate, contributing to improved livestock sustainability.
Anti-aliased Convolutional Neural Networks (CNNs) have been proposed to overcome the shift variant nature of the CNNs. The fundamental building block of the anti-aliased CNN has been the application of Gaussian or wavelet-based smoothing before the pooling operation. However, in all these approaches, the feature maps’ edges are also smoothed while suppressing high-frequency components. In this work, two novel pooling approaches are presented, namely the Laplacian-Gaussian Concatenation with Attention (LGCA) pooling and Wavelet-based Approximate-Detailed Coefficient concatenation with Attention (WADCA) that can preserve the edges in the feature maps. The results suggest that the proposed pooling approaches outperform conventional as well as blur pooling for classification, segmentation and auto-encoders. In terms of average binary classification accuracy (cats vs dogs), the proposed LGCA approach outperforms the conventional pooling and blur pooling by 4% and 2%, 3% and 4%, 3% and 0.5% for MobileNetv2, DenseNet121 and ResNet50 respectively. On the other hand, the proposed WADCA approach outperforms the normal pooling and blur pooling by 5% and 3%, 2% and 3%, 2% and 0.17% for MobileNetv2, DenseNet121 and ResNet50 respectively. It is also observed from the results that edge-preserving pooling does not have any significance in segmentation tasks possibly due to high to low-resolution translation. Meanwhile, high-resolution reconstruction has been observed for the LGCA pooling in the case of convolutional auto-encoders.
Developing low-cost and reliable sensor systems for the detection of trace amounts of toxic gases is an important area of research. Ammonia (NH3) is a commonly produced industrial chemical and a harmful colorless pungent gas released from various manufacturing and processing industries. Continuous exposure to NH3 vapor causes serious menace to human health, microorganisms, and the ecosystem. Exposure to relatively higher concentrations of NH3 severely affects the respiratory system and leads to kidney failure, nasal erosion ulcers, and gastrointestinal diseases. Excessive accumulation of NH3 in the biosphere can cause various metabolic disruptions. As a consequence of this, therefore, suitable sensing methods for selective detection and quantification of trace amounts of NH3 are of utmost need to protect the environment and living systems. Given this, there have been significant research advances in the preceding years on the development of fluorescence chemosensors for efficient sensing and monitoring of the trace concentration of NH3 both in solution and vapor phases. This review article highlights several fluorescence chemosensors reported until recently for sensing and quantifying NH3 in the vapor phase or ammonium ions (NH4+) in the solution phase. The wide variety of fluorescence chemosensors discussed in this article are systematically gathered according to their structures, functional properties, and fluorescence sensing properties. Finally, the usefulness and existing challenges of using the fluorescence-based sensing method for NH3 detection and the future perspective on this research area have also been highlighted.
This work demonstrates a novel linear-circular wideband transmission type polarization converter for K-and Ka-band applications. The unitcell comprises primarily two FSSs on both sides of a thin dielectric substrate. For a linear polarized wave incidence, the transmitted wave is circularly polarized with a minimum 3 dB Axial Ratio (AR) from 19.08-37.27 GHz with a relative bandwidth of 64.56% and near 0 dB AR at two frequencies, 24.4 GHz and 34.8 GHz. The response is angular stable, almost up to 45 o for different oblique incidences under Transverse Electric (TE) and Transverse Magnetic (TM) modes. Electric field patterns are also investigated to visualize the circular polarization rotation sense. The unitcell is compact with a structural periodicity of 0.102λL×0.134λL and thickness of 0.051λL, where λL is the free-space wavelength corresponding to the lowest operating frequency. In addition, this design offers a bandwidth tunability feature by adjusting the stub's length at the back FSS. Since the design is miniaturized with 0.697(/) volume and wideband stable angular performance made, this a potential candidate for real-time satellite applications.
A novel transmission type polarizer for K-and Ka-band applications is demonstrated in this work. A thin dielectric substrate is sandwiched between the top and bottom Frequency Selective Surfaces (FSSs) that comprise the polarizer's unitcell. The transmitted wave is circularly polarized for the linearly polarized wave incidence, with a minimum 3dB Axial Ratio (AR) over the frequency from 16.52-39.93 GHz (82.94% relative bandwidth). The performance is stable up to 45 o for Transverse Electric (TE) and Transverse Magnetic (TM) incidences. The equivalent circuit model of the polarizer is extracted, and the response agrees with the EM solver results. The possibility to perceive the circular polarization rotation sense is captured by studying electric field patterns at two frequencies. The design is compact with a structural periodicity of 0.088λL × 0.116λL and thickness of 0.044λL, where λL is the free-space wavelength corresponds to the lowest frequency of the operating range. The minimum Polarization Extinction Ratio (PER) of 21 dB is observed over the entire operating range. Realtime satellite applications could benefit from the miniaturized volumetric design 0.448(/1000) and the stable angular response of the presented wideband polarizer.
The determination of neurotransmitters and adrenoreceptor drugs is highly essential due to their specific functions in the human body. In this work, the determination of carvedilol (CAR) and dopamine (DA) was carried out using carbon cloth (CC), which was modified using a facile strategy of drop-casting dimethyl sulfoxide (DMSO). This induced the formation of functional groups without any loss in the structural integrity of CC. The DMSO modified CC (CC-DMSO) was used for the detection of CAR in the range of 1 nM to 10 μM with a limit of detection (LOD) of 120 pM. Similarly, the CC-DMSO was able to detect DA in the range of 10 pM to 10 μM with a highly promising LOD of 0.3 pM. A bending test was also carried out on the electrode and it could be seen that only a negligible variation in sensing capability was observed when the electrode was in the bent form. In addition, the detection of CAR and DA was also carried out in real samples such as human serum. This study reveals that this modification strategy can serve as a versatile and flexible sensing platform for the detection of CAR and DA together in real world medical scenarios.
Detection of hydrogen peroxide (H2O2) from cell cultures is important for monitoring different diseases. Here, g-C3N4 (gCN) was incorporated into well-defined clusters of RuW (RuW-gCN) through monomer complexation of Ru-substituted phosphotungstate and melamine for electrochemical detection of H2O2. RuW-gCN exhibited enhanced electrochemical sensing properties in comparison to its constituents due to the synergic effects between RuW and gCN. The characterization of RuW-gCN revealed successful complexation to form the composite in addition to the presence of a layered structure of gCN. The electrochemical sensor made of RuW-gCN was able to detect H2O2 with a detection limit of 46 nM in the linear ranges from 100 nM to 50 μM and from 50 μM to 1 mM. The developed sensor was employed for the selective detection of H2O2 in the presence of analytes like ascorbic acid (AA), dopamine, and glucose in addition to being stable even after a week of storage at room temperature. It has also been verified for real sample application by detecting H2O2 produced by cancer cells as a result of an AA trigger.
Organic polymers are widely explored due to their high stability, scalability, and more facile modification properties. We developed cost-effective dithiocarbamate-based organic polymers synthesized using diamides, carbon disulfide, and diamines to apply for environmental remediation. The sequestration of radioiodine is a serious concern to tackle when dealing with nuclear power for energy requirements. However, many of the current sorbents have the problem of slower adsorption for removing iodine. In this report, we discuss the utilization of an electron-rich dithiocarbamate-based organic polymer for the removal of iodine in a very short time and with high uptake. Our material showed 2.8 g/g uptake of vapor iodine in 1 h, 915.19 mg/g uptake of iodine from cyclohexane within 5 s, 93% removal of saturated iodine from water in 1 min, and 1250 mg/g uptake of triiodide ions from water within 30 s. To the best of our knowledge, the iodine capture was faster than previously observed for any existing material. The material was fully recyclable when applied for up to four cycles. Hence, this dithiocarbamate-based polymer can be a promising system for the fast removal of various forms of iodine and, thus, enhance environmental security.
The joining of dissimilar hard metals such as high-strength steel and nickel-based alloy is required for shipbuilding and offshore applications to enhance the strength, fracture toughness, and corrosion resistance of the exposed parts. However, the joining of these dissimilar alloys has remained a major challenge due to the limited solubility of Fe and Ni in each other, which commonly results in the formation of brittle intermetallic compounds. We present here a novel investigation on the joining of overlapped nickel-based alloy 625 and marine-grade GL E36 steel plates by friction stir lap welding (FSLW). The interface microstructure and its influence on joint strength are rigorously tested. The main bonding mechanism is found to be the mechanical mixing of Fe and Ni along the interface. The interface thermal cycles are computed by a three-dimensional numerical heat transfer model and their effects on the microstructure are examined. Multiple micro tensile specimens are extracted from the stir zone to examine the through-thickness variation in the stir zone properties. The welded joint is characterized further by evaluating the interface microhardness distribution, lap-shear strength, and surface residual stresses.
We retrospectively analyzed the immunopotentiating mechanism of an oil-in-water (O/W) emulsion-based vaccine adjuvant LiteVax™ Adjuvant (LVA) that contains CMS (Maltose 4’-monosulphate 1,2,3,6,2’,3’,6’-heptadecanoic acid ester), squalane, Tween 80 in phosphate buffered saline. Despite being effective in animal models, the immunological mechanisms by which LVA exerts adjuvant function are not known. As dendritic cells (DC) are key for initiating and propagating the immune response, we have investigated the effect of LVA and of its components on the DC function. We show that CMS but not LVA significantly enhances the expression of DC activation-associated markers, cytokine secretion, and CD4+ T cell responses. On the other hand, CMS ZERO [non-sulphated sucrose fatty acid esters (ZERO)], used as a control, had no such activity. Our data identified the unique nature of CMS in LVA, and propose that LVA acts as a delivery system, and CMS acts as an immunostimulatory agent.
Serotonin (5-hydroxytryptamine (5-HT)) is one of the important neurotransmitters which is released from the endocrine system. An abnormal level of this biomarker leads to several neurological diseases. The accurate assessment of serotonin is the utmost option to start treatment in the early stages of the disease. The current work is focused on the development of a disposable, screen-printed electrochemical sensor for the depression biomarker, serotonin in the physiological pH medium (pH 7.4) with the aid of a hexagonal, Ni(OH)2-nanoplate (NH-HNP)-embedded chitosan (Chit) and modified, screen-printed carbon electrode (SPCE). Initially, hexagonal nanoplates of Ni(OH)2 were synthesized by an eco-friendly and simple hydrothermal method. The prepared materials were well characterized by advanced analytical techniques to examine the physicochemical properties of the synthesized Ni(OH)2 hexagonal nanoplates. From the cyclic voltametric (CV) analysis, it was found that the oxidative current response of 5-HT at a NH-HNP-modified SPCE has about fivefold higher current values than over bare SPCE. The scan rate studies of NH-HNP-Chit/SPCE electrodes revealed that the oxidation mechanism of 5-HT is controlled by the diffusion behavior of the analyte. Differential pulse voltammetric tests of the NH-HNP-Chit/SPCE electrode exhibited a linear response in the dynamic concentration range of 0.1 to 30 µM, with a detection limit of about 60 nM. The sensor response is very reproducible from electrode to electrode, and the deactivation or surface-fouling of the sensor was not observed within the several experimental measurements. The sensor exhibited excellent storage stability over a period of twenty days. Finally, the fabricated, disposable SPCE sensor has shown respectable activity for the detection of depression biomarker 5-HT from synthetic urine and saliva samples.
This paper studies the improvement in machining performance by implementing a hybrid coolant approach for the machining of difficult-to-machine Inconel 625 superalloy. This study differs from the pre-existing hybrid cooling methods by using a novel modified tool holder for the supply of cryogenic coolant. An external nozzle is also involved as part of the coolant system to provide MQL spray to the cutting zone in hybrid cooling. Turning experiments using MQL, cryogenic cooling with an external nozzle, cryogenic cooling with a modified tool holder and hybrid cryo-MQL cooling were performed at different parameter levels to analyze the machining performance of the proposed new cooling technique. The results show that a maximum reduction of 30.52%, 63.67%, and 43.27% was observed for surface roughness, tool wear, and cutting forces using the hybrid cooling technique. The tool wear types and mechanisms underlying the wear formation when using various techniques for cooling are studied using SEM imaging of tooltips. Also, the chip morphology study was carried out to compare the effects on machinability.
A novel class of organic polymer (OP) with customizable functional groups in the backbone and side-chain was designed and synthesized to remove toxic Hg ²⁺ ions from contaminated water within 30 seconds using a simple spin column technique.
A cleft-shaped 2-picolyl-4-amino-1,8-naphthalimide Tröger’s base (TBNap) was synthesized and employed as a fluorescent ‘turn-on’ chemosensor for the discriminative sensing of volatile halogenated solvents based on the ICT sensing mechanism. TBNap...
The high penetration of inverter-based resources (IBRs) will substantially change the dynamic behavior of the power system including inertia distribution. Real-time inertia distribution monitoring is important to support power system operation in future low inertia grids. This article presents the development and validation of a center of power-based inertia distribution estimation technique utilizing the measurements available from the phasor measurement units of the wide-area measurement systems. The suggested technique is validated on the 246-bus northern regional power grid of Indian power system. The impact of different penetration levels of IBRs on the proposed inertia distribution index (IDI) is also studied. The suggested index works purely on power system measurements and does not need any model information. Further, the impact of change in IDI on oscillation baselining study is explored.
VOCs are volatile organic compounds that are produced naturally as well as due to anthropogenic activities. The application of VOCs ranges from being a biological chemical signal to a metabolic product to a serious pollutant. VOCs are gaining significance in the context of biology, diagnostics, sustainability as well as a healthy lifestyle. In this article, an overview of VOCs, their sources and their applications are discussed.
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526 members
Praveen .G
  • Global Sanitation Centre of Excellence
Pathath Abdul Rasheed
  • Biological Sciences and Engineering
Dinesh Setti
  • Mechanical Engineering
A.P. Vinod
  • Electrical Engineering
S. H. Kulkarni
  • Department of Mathematics
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Pālghāt, India
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https://iitpkd.ac.in/