IR@CMERI - The Central Mechanical Engineering Research Institute (CSIR)
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Sensing of Higher Alcohols and Selective Sensing of Iso-Amyl Alcohol by Poly (o-Phenylenediamine) Nanofiber
No full textNanofiber of semiconducting poly(o-phenylen-ediamine) (PoPD) with free =NH functional groups synthesized in dimethyl sulfoxide by reverse salting-out process was employed as chemiresistive sensor for the successful sensing of aliphatic alcohols vapor. The resistivity of PoPD nanofiber in its self-charge separated form was decreased upon exposure of various alcohol vapor, viz., methanol, ethanol, propanol, isopropanol, n-butanol, t-butanol, 1-pentanol, and hexanol with air mixture at room temperature (30±2 °C) and room humidity (65±5%). The film of PoPD nanofiber was responded strongly towards the methanol and ethanol vapor irrespective of their concentration above 50 ppm with air flow due to having strong interaction with such small molecules. However, the vapor of higher alcohols at room temperature could also be detected considering their differences in the % responses at varying concentrations. Interestingly, the film of PoPD nanofiber could be used for selective sensing of iso-amyl alcohol vapor, as the resistivity was increased in presence of vapor of iso-amyl alcohol with air. The sensing mechanism was established on the basis of the different interactions of PoPD nanofiber with the aliphatic alcohols analyzed from the spectroscopic characterizations
Letter to the Editor: Comments on the paper of Batagelj—on fractional approach to analysis of linked networks
No full textWe examine the role of count conservation when derived network matrices are obtained from linked network matrices using an outer product decomposition. It is seen that a full counting operation conserves the count of pathways between nodal variables while a fractional counting operation conserves the count of the nodal variable. We use the cases of co-referencing (bibliographic coupling) and co-citation with a simple citation network to illustrate the ideas
Investigation of the mechanical performance of carbon/polypropylene 2D and 3D woven composites manufactured through multi-step impregnation processes
No full textIn this work, pre-impregnation techniques including Dr. Ernst Fehrer (DREF) spinning and electrostatic powder coating were used to negate the poor impregnation of highly viscous thermoplastics. The DREF spun hybrid yarns and electrostatic spray coated towpregs were woven into 2D and 3D fabrics and subsequently consolidated to yield two variations of 2D and four variations of 3D composites including 3D angle inter-lock and 3D orthogonal weave. The 2D composites possessed higher tensile and flexural strength than the 3D composites. However, better notch impact properties were observed for 3D orthogonal weave. The closer wrapping in 3D orthogonal slightly improves the shock absorption capability of the composite than the angle interlock composite. Composites made from powder coated towpregs performed better than composites made from DREF spun hybrid yarns, minimizing the effect of the weave pattern. Porosity was a common feature of composites manufactured from DREF spun yarns as observed from micro-CT images
Alteration in capacitive performance of Sn-decorated MnO2 with different crystal structure: An investigation towards the development of high-performance supercapacitor electrode materials
No full textHetero atom doped-MnO2 is considered as the promising supercapacitor electrode material due to its high capacitance properties. Depending on the way of MnO6 octahedra interlinking, it can form different types of crystal structure (α, β, γ, δ). The capacitance properties of MnO2 depend on the cation intercalation/de-intercalation and the type of crystallographic structures. This study emphasises the phase and interlayer spacing control synthesis of Sn-incorporated MnO2 (α, β, γ, δ crystal form) through a facile one-pot hydrothermal technique by using verities of starting materials. The specific capacitance of MnO2 depends on different crystal structure and the effect of hetero atom introduction. Sn-decorated β-MnO2 (β-SM) exhibits high specific capacitance of ~1957 F g−1 at 2 A g−1 in a three-electrode system. An asymmetric supercapacitor (ASC) is configured by intriguing high capacity β-SM as positive electrode and thermally reduced graphene oxide (TRGO) as negative electrode in the potential window of 1.4 V. The ASC delivers the maximum specific energy of ~29.79 W h kg−1 with a specific power of ~1625.31 W kg−1 at the current density of 2 A g−1. The ASC shows good cycle life of ~94% retention in specific capacitance after 10,000 charge-discharge cycles at 15 A g−1 current density
A bottom-up approach to experimentally investigate the deposition of austenitic stainless steel in laser direct metal deposition system
No full textDirect metal deposition (DMD) is a method of metallic part fabrication under the classification of additive manufacturing process. In DMD, parts are manufactured by melting powder particles reaching the deposition zone, layer by layer with a laser beam. This potential process promises manufacturing flexibility of complex shapes deposition with a range of challenging materials. The work presents the establishment of laser, powder and deposition parameters in a newly developed metal-based direct laser deposition system. The experiments are performed using a 1.2-kW diode laser of 976-nm wavelength coupled with coaxial fed powder delivery nozzle. Geometrical characteristics and mechanical properties of the deposited single-wall, multi-layer wall are determined and discussed. The study also discusses some of the challenges met during the deposition and their potential resolutions. Issues with uniformity of layer width, layer height and mechanical properties such as surface finish and micro-hardness are addressed. The specific aim of this experimental work is to effectively control the process parameters towards building a sound thin wall clad deposition and to further use those parameters for the development of a functional 3D component. A 3D functional component is deposited using 300 W laser power, 4 mm/s scanning speed, 1.05 g/min powder feed rate and 50% overlap ratio which shows a good geometrical resemblance with the original part. The study thus can provide intuitive guidance for deposition to metal additive manufacturing enthusiasts
Saliency Subtraction Inspired Automated Event Detection in Underwater Environments
No full textUnmanned underwater exploration in unconstrained environments is a challenging problem. Analysis of the large volumes of images/videos captured by underwater stations/vehicles manually is a major bottleneck for further research. Existing computer vision methods either do not target unconstrained underwater environments or they only aim to detect static or moving entities. In this paper, we present a novel method for analyzing underwater videos and detecting events. Entry/exit of an object in scene is treated as an event independent of the other objects present therein. The method is applied on underwater videos with no prior knowledge, thus aiding in automated underwater exploration. The method is inspired by the fact that saliency of objects in the scene is invariant of the surrounding environment. The proposed method is composed of three main steps: Local Patch Saliency, Adaptive Saliency Subtraction, and event generation for analyzing underwater imagery from the videos. The method is aimed at detecting overlapping events containing man-made as well as natural objects including those containing multiple objects in the unconstrained underwater conditions. The performance of the method is evaluated on publicly available videos obtained from Ocean Networks Canada and Fish4Knowledge datasets. Ground truth for Ocean Networks Canada videos is not available; hence, a method for generating the same for varied sources is also presented. The algorithm achieves a precision of 98% for event detection with 20% misclassification rate. The results show the robustness of the method that performs even in complex and varying underwater conditions
Feasibility Study on Thermography of Embedded Tumor Using Fiber Bragg Grating Thermal Sensor
No full textThermal imaging is one of the emerging non-invasive neuro-imaging techniques utilized for demarcation of intra-axial brain tumor borders. Tissue regions comprising of tumors is known to attain higher temperature on the surface due to the increased rate of blood flow and cell metabolism and therefore the variation in tissue surface temperature may be accounted as an indicator of a tumor existence. In the present work, Fiber Bragg Grating based Thermal Sensor (FBGTS) is developed for temperature measurement of a simulated tissue based on Agar material which mimics the soft tissue of brain. A heater is embedded inside the simulated tissue which mimics the tumor's temperature variation inside the brain. The temperature of the embedded heater along with the surface temperature of the simulated tissue is acquired simultaneously using two FBGTS probes. Further, the temperature variations on the surface of the simulated tissue are studied for varying heater temperatures as well as for the varying position of the heater inside the simulated tissue, indicating varying positions of brain tumors. The present study proposes and demonstrates the feasibility of using FBGTS for thermography from which the possible detection and approximate position of an existing brain tumor can be evaluated
Optimal Feet-Forces’ and Torque Distributions of Six-Legged Robot Maneuvering on Various Terrains
No full textAn analytical model with coupled dynamics for a realistic six-legged robotic system locomoting on various terrains has been developed, and its effectiveness has been proven through computer simulations and validated using virtual prototyping tools and real experiment. The approach is new and has not been attempted before. This study investigated the optimal feet-forces’ distributions under body force and foot–ground interaction considering compliant contact and friction force models for the feet undergoing slip. The kinematic model with 114 implicit constraints in 3D Cartesian space has been transformed in terms of generalized coordinates with a reduced explicit set of 24 constrained equations using kinematic transformations. The nonlinear constrained inverse dynamics model of the system has been formulated as a coupled dynamical problem using Newton–Euler method with realistic environmental conditions (compliant foot–ground contact, impact, and friction) and computed using optimization techniques due to its indeterminate nature. One case study has been carried out to validate the analytical data with the simulated ones executed in MSC.ADAMS® (Automated Dynamic Analysis of Mechanical Systems), while the other case study has been conducted to validate the analytical and simulated data with the experimental ones. In both these cases, results are found to be in close agreement, which proves the efficacy of the model
Three-dimensional phase field simulation of spheroidal grain formation during semi solid processing of Al-7Si-0.3 Mg alloy
No full textThe present study reports development and application of a three dimensional phase field (PF) model, to investigate the microstructure evolution mechanism responsible for generation of spheroidal primary Al grains, associated with cooling slope processed semi solid slurry of A356 aluminium alloy. The cooling slope rheoprocessing technique involves solidification of flowing melt on an inclined slope surface, where gravity assisted fluid flow and shearing action between the flowing melt and the slope surface causes formation of near spherical primary solid fragments, and subsequent isothermal globularisation of the evolving primary solid. The present PF model implements a seed density based nucleation model. The seed density requirements to simulate microstructure evolution for different simulation/melt treatment conditions of cooling slope processing have been estimated based on initial experimentation. The simulated micrograph of slope exit state i.e, at the end of cooling slope processing has been used to estimate the number density and average size of constituent α-Al grains of the generated slurry, at slope exit state. The values obtained are fed subsequently as input parameters to simulate post slurry generation isothermal globularisation process. The model predictions are validated experimentally, thus establishing its capability to predict the characteristics of semisolid slurry at different stages of cooling slope rheoprocessing, in terms of solid content (volume fraction), diameter, density, and shape factor (sphericity) of nucleated primary Al grains
Discerning Detection of Mutagenic Biopollutant TNP from Water and Soil Samples with Transition Metal-Containing Luminescence Metal–Organic Frameworks
No full textTwo luminescent MOFs, Mn@MOF and Cd@MOF, have been reported herein, which are capable of selectively detecting 2,4,6-trinitrophenol (TNP), one of the potent organic water pollutants in the class of mutagenic explosive nitroaromatic compounds (epNACs). It is perceived that the d10-based Cd(II)-constituting MOF shows a better response in the realm of TNP-like nitroaromatic sensing in comparison to the d5-based Mn@MOF which may possess lower electron density over the conjugated building blocks. The sensing competences of these chemosensors have been explored by means of various spectroscopic experimentations, and it is observed that for both d5 and d10-containing MOFs, the initial fluorescence intensity is significantly quenched in response to an aqueous solution of TNP. However, Cd@MOF is more selective and sensitive toward TNP over several other epNACs than Mn@MOF. The high chemical stability of the MOF samples, as well as its amusing sensing efficiency of Cd@MOF, further instigated to investigate the sensing ability in various environmental specimens like soil and water culled from several zones of West Bengal, India