Browsing by Author "Mishra M."

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A comparative study of regression, neural network and neuro-fuzzy inference system for determining the compressive strength of brick�mortar masonry by fusing nondestructive testing data
(2019) Mishra M.; Bhatia A.S.; Maity D.
Determining the compressive strength of masonry structures is critical for assessing their service life and thus providing safety assurances to their occupants and valued stakeholders. This paper presents a methodology based on various data fusion systems for predicting the compressive strength using data collected from nondestructive testing. According to the experimental readings obtained from the laboratory tests for masonry wallettes, 44 samples are used to construct the training datasets and results validated against a masonry structure located in Kharagpur. The compressive strength of masonry units is predicted using statistical regression models and other state-of-the-art approaches. Two indices, namely the coefficient of determination (R2) and root mean square error, are used to test the performance of different models. The results indicate that both neural network and neuro-fuzzy inference system have a superior predictive capacity than other models and can be reliably employed in the field to evaluate the compressive strength of brick�mortar masonry structures. � 2019, Springer-Verlag London Ltd., part of Springer Nature.
Erratum: Truncated hexagonal bi-pyramidal gallium ferrite nanocrystals: Integration of structural details with visible-light photo-activity and self-cleaning properties (Journal of Materials Chemistry A (2018) DOI: 10.1039/c8ta02749h)
(2018) Mishra M.; Mukherjee I.; Mall A.K.; Mitra A.; Dash S.; Chatterjee S.; Mukherjee S.; Roy A.
Correction for 'Truncated hexagonal bi-pyramidal gallium ferrite nanocrystals: integration of structural details with visible-light photo-activity and self-cleaning properties' by Monali Mishra et al., J. Mater. Chem. A, 2018, DOI: 10.1039/c8ta02749h. � 2018 The Royal Society of Chemistry.
Experimental evaluation of the behaviour of bamboo-reinforced beam�column joints
(2019) Mishra M.; Kumar M.K.; Maity D.
The housing industry has a high energy consumption because of the widespread use of items such as concrete and steel for construction. Consequently, researchers have explored the use of bamboo, which is an eco-friendly material, as an alternative to steel in the construction of buildings. Bamboo is already used for constructing various structural members, such as beams, columns, slabs, and walls. However, no study has been performed on the behaviour of beam�column joints made of bamboo reinforcement. The present study focused on using bamboo as an alternative reinforcing material in beam�column joints. A series of laboratory tests were conducted for investigating the mechanical properties of bamboo. The failure of six full-scale bamboo-reinforced beam�column joints in a reaction frame was examined. Furthermore, the effectiveness of different configurations of beam�column joints was investigated in terms of the load�deformation characteristics, ultimate moment, cracking behaviour, and failure patterns through experimental testing. A comparative study of bamboo-reinforced beam�column joints with and without water-repellent treatment and steel-reinforced beam�column joints is conducted. The ultimate load-carrying capacity of the bamboo-reinforced beam�column joints was considerably larger than that of joints without any water-repellent treatment. The performance of steel-reinforced concrete joints was marginally better than that of bamboo-reinforced concrete joints. � 2019, Springer Nature Switzerland AG.
Flexible nano-GFO/PVDF piezoelectric-polymer nano-composite films for mechanical energy harvesting
(2018) Mishra M.; Roy A.; Dash S.; Mukherjee S.
Owing to the persistent quest of renewable energy technology, piezoelectric energy harvesters are gathering considerable research interest due to their potential in driving microelectronic devices with small power requirement. Electrical energy (milli to microwatt range) is generated from mechanical counterparts such as vibrations of machines, human motion, flowing water etc. based on the principles of piezoelectricity. Flexible high piezoelectric constant (d33) ceramic/polymer composites are crucial components for fabricating these energy harvesters. The polymer composites composed of gallium ferrite nanoparticles and polyvinylidene fluoride (PVDF) as the matrix have been synthesized by solvent casting method. First, 8 wt. % PVDF was dissolved in DMF and then different compositions of GaFeO3 or GFO (10, 20, 30 wt. %) (with respect to PVDF only) nanocomposites were synthesized. The phase of the synthesized nanocomposites were studied by X- Ray diffraction which shows that with the increase in the GFO concentration, the intensity of diffraction peaks of PVDF steadily decreased and GFO peaks became increasingly sharp. As the concentration of GFO increases in the PVDF polymer matrix, band gap is also increased albeit to a small extent. The maximum measured output voltage and current during mechanical pressing and releasing conditions were found to be ? 3.5 volt and 4 nA, respectively in 30 wt % GFO-PVDF composite, comparable to the available literature. � Published under licence by IOP Publishing Ltd.
Machine learning techniques for structural health monitoring of heritage buildings: A state-of-the-art review and case studies
(2021) Mishra M.
This paper performed a systematic review of the various machine learning (ML) techniques applied to assess the health condition of heritage buildings. More robust predictive models can be obtained through the effective utilisation of test data gathered from the laboratory or field combined with ML. These models can be used for several predictive applications such as predicting the compressive strength of masonry or repair mortars, possible damage scenarios in heritage buildings, seismic vulnerability assessment, determination of the mechanical properties of materials, and superficial damages on the surface of the monument due to weathering effects, material loss, efflorescence, seepage, algae growth, and moss deposition. The case studies of several interesting and diverse applications of ML, such as its use in strengthening applications, are also discussed. Indirect factors that must be determined to quantify the extent of damage such as moisture content, cracks, and amount of deposited dust in heritage buildings, are also discussed. Furthermore, future research directions and challenges in applying the ML techniques in the case of heritage buildings are highlighted. � 2020 Elsevier Masson SAS
Modeling of Landslide�Tunnel Interaction: the Varco d�Izzo Case Study
(2019) Vassallo R.; Mishra M.; Santarsiero G.; Masi A.
This paper reports a case study of the interaction between a slow-moving landslide in clay soil and a railway tunnel protected by sheet pile walls, that crosses the landslide accumulation. The earthflow, that develops in the Southern Apennines, Italy, has been long studied and monitored by different organizations, such as the national railway company and the University of Basilicata. Since the investigated landslide and construction typologies are quite diffused in mountainous areas, the case study can be considered representative of a large number of other similar cases. Differently from other approaches proposed in the literature, the role of the landslide slip surface depth, changing in the directions longitudinal and transversal to the tunnel, and of structural connections, affecting the pile�tunnel system response, are accounted for in detail. Several numerical models are used to simulate the interaction between the sliding soil and tunnel. Different 2D and 3D geotechnical and structural models are adopted to reproduce stress�strain scenarios compatible with the experimental evidence. The modeling results indicate that the interaction varies considerably along the tunnel length because of the 3D geometry of the landslide, and is conditioned by the residual shear strength available on the slip surface. The expansion joints in the tunnel lining only marginally influence the stress in the structure because of the presence of the adjacent sheet pile walls, which enable considerable collaboration between the tunnel sectors. � 2019, Springer Nature Switzerland AG.
Multiverse Optimisation Algorithm for Capturing the Critical Slip Surface in Slope Stability Analysis
(2020) Mishra M.; Ramana G.V.; Maity D.
In professional practice, slope stability assessment of natural or man-made slopes is performed using traditional limit-equilibrium-based methods. These methods often fail to identify the critical slip surface corresponding to the minimum factor of safety (FS). Optimisation methods based on stochastic search techniques can more easily locate the global optima solution than traditional methods can. The paper presents the application of the recently proposed multiverse optimisation (MVO) algorithm in determining the lowest FS along the critical slip surface. Four benchmark examples are analysed to test the performance of the multiverse optimiser for slope stability assessment. The results demonstrate that the MVO algorithm can capture the critical slip surface and compute its corresponding FS with a considerably low uncertainty. � 2019, Springer Nature Switzerland AG.
Performance Studies of 10 Metaheuristic Techniques in Determination of Damages for Large-Scale Spatial Trusses from Changes in Vibration Responses
(2020) Mishra M.; Barman S.K.; Maity D.; Maiti D.K.
The determination of the location and severity of damage is a crucial task in the damage assessment of structures. In this study, 10 population-based metaheuristic techniques are applied to identify the location and severity of damage in large-scale spatial truss structures. Two examples from the relevant literature are considered under various damage settings to compare the efficacy of the recent swarm intelligence-based optimization methods. A combined natural frequencies and mode shapes-based objective function has been used in the present study for the damage detection purpose. The effect of noise is incorporated in the dynamic responses to study the efficiency of the best algorithm out of 10 possibilities in identifying damages in noisy environments. The results indicate the superiority of teaching-learning-based optimization (TLBO) technique over other optimization techniques in identifying damages with effective precision. Furthermore, with TLBO the number of function evaluations and computation time required in the optimization process is substantially reduced. � 2019 American Society of Civil Engineers.
Room temperature multiferroism in polycrystalline thin films of gallium ferrite
(2017) Mishra M.; Roy A.; Garg A.; Gupta R.; Mukherjee S.
We have synthesized (010) textured polycrystalline thin films of gallium ferrite (GaFeO3 or GFO) on n-Si(100) and Pt/Si(111) substrates using sol-gel assisted spin coating technique. Structural characterization using x-ray diffraction and Raman spectroscopy confirms formation of single phase with crystallite size ?37�47 nm. Magnetic characterization demonstrates saturated magnetic hysteresis loop at room temperature and indicates that due to reduced crystallite size, ferri to paramagnetic transition temperature, TC ?300 K is higher compared to bulk GFO, reported earlier. Room temperature piezo-response force microscopic analysis reveals local ?180� phase switching of ferroelectric domains at very high coercive field, ?700 kV/cm, consistent with recent experimental and first-principles studies. Our study opens up the possibility of integrating polycrystalline GFO in novel room temperature multiferroic devices. � 2017 Elsevier B.V.
Truncated hexagonal bi-pyramidal gallium ferrite nanocrystals: Integration of structural details with visible-light photo-activity and self-cleaning properties
(2018) Mishra M.; Mukherjee I.; Mall A.K.; Mitra A.; Dash S.; Chatterjee S.; Mukherjee S.; Roy A.
We report the growth of gallium ferrite (GaFeO3 or GFO) nanocrystals with a unique morphology, "truncated hexagonal bi-pyramid" (THBP), and with a novel orthorhombic P212121 symmetry under hydrothermal conditions in pure water without using any reducing or shape defining reagent. The growth conditions of such a structure are optimized through a detailed study using field emission scanning electron microscopy. The structural details of the above hitherto unreported phase of the material are studied using room temperature powder X-ray diffraction (XRD), Raman spectroscopy, high resolution transmission electron microscopy and ab initio electronic structure calculations. In light of the above structural characterization, a possible mechanism for the formation of the specific shape of hexagonal bi-pyramid is proposed. Our investigations on optical, photocatalytical and wetting characteristics of the as-grown nanocrystals demonstrate their visible light photocatalytic activity as well as a strong-hydrophilic character. The material is poised to establish itself as a new "self-cleaning" material. � 2018 The Royal Society of Chemistry.
Unconventional magnetism in ZnO nanorods
(2017) Mishra D.; Rout C.S.; Mishra M.; Pattanaik A.K.
We report room temperature ferromagnetism in vacuum annealed ZnO nanorods. ZnO nanorods were annealed at 600�C for 6�hours in an annealing chamber with a pressure of 10?6 Torr. Our study indicates that ZnO nanorods develop room temperature ferromagnetism due to the presence of oxygen vacancy defects in it. Presence of large surface area of nanorods and oxygen vacancy are mainly responsible for the observed magnetic behavior. � 2017 Taylor & Francis Group, LLC.