Indian Institute of Technology Bombay
  • Mumbai, Maharashtra, India
Recent publications
Historically, the surface water holding structures have been a primary water source for the people of Madurai, a South-Indian city in Tamil Nadu, India. Since the 1990s, the city has been experiencing rapid urbanization. The encroachment issues have started degrading the river Vaigai and system of water holding tanks called the Vandiyur tank cascade system (VTCS). Due to limited holistic hydrological understanding of the region, conservation efforts at VTCS have limited efficiency. To increase understanding of the regional hydrology, this study analyzed normal and actual annual rainfall for the district based on the 50 years of IMD data (1969–2018). The LULC change was studied using remote sensing images from 2002 to 2018. Results indicated that rainfall, with an average percentage departure of 22%, recorded an overall reduction of 11.2% during N–E monsoon and 10.6% during S–W monsoon. Using aerial imagery, a rapid increase in the urban catchments, up to 330%, and the curve number, up to 86%, was recorded in peri-urban and urban catchments. As a result of this, water availability in VTCS was observed to be highly fluctuating (5 to 100%). Field investigation further revealed that about 30 to 70% of the total volume of the tanks was occupied by the silt and muck deposited either from the upstream tanks or due to sewage discharge. Subsequently, the practice of tank-fed agriculture became limited to one season from previously two or three seasons. Reviving VTCS was the most pressing recommendation discussed that would possibly provide scope for holistic ground-surface water management.
The vast semi-arid Southern peninsular region of India is irrigated using a traditional surface water infrastructure called Tank Cascade Systems (TCS). The TCS is a common-property resource that was constructed about 2000 years ago and has been managed since then for generations using public-participatory approaches. Furthermore, the application of TCS is not only limited to irrigation but also domestic water supply, livestock management, retarding negative impacts from extreme events such as seasonal flooding and recurrent droughts. In addition, the indirect benefits of TCS in providing environmental services, being essentially controlling the micro-climatic conditions, are numerous. However, TCS has been degrading since the colonial rule due to limited TCS management. The policy on the rights to manage minor irrigation works (tank irrigation) lies in the hands of the estate continued even during the post-independence period. As a consequence, the rural economy and livelihood security, which was essentially dependent on TCS, collapsed. Nevertheless, since the 1980s, the Indian Government started realizing the significance of traditional TCS in the view of climate change, rapid urbanization, and demographic explosion. Several schemes and programs were launched in bilateral associations with local and foreign agencies including the World Bank. The evidence indicated that the policy interventions in regards to scientific revival and ecological restoration, and rehabilitation of tanks for providing substantial benefits to the stakeholders (farmers and local communities) are rational. Interventions for tank management are much-needed with a case-to-case approach rather than implementing the ideology of one model fits all.
Biaryl scaffolds are found in natural products and drug molecules and exhibit a wide range of biological activities. In past decade, the transition metal-catalyzed C–H arylation reaction came out as an effective tool for the construction of biaryl motifs. However, traditional transition metal-catalyzed C–H arylation reactions have limitations like harsh reaction conditions, narrow substrate scope, use of additives etc. and therefore encouraged synthetic chemists to look for alternate greener approaches. This review aims to draw a general overview on C–H bond arylation reactions for the formation of C–C bonds with the aid of different methodologies, majorly highlighting on greener and sustainable approaches.
The present study focuses on the inorganic geochemical features of the bituminous coal samples from the Raniganj and the Jharia Basins, as well as the anthracite samples from the Himalayan fold-thrust belts of Sikkim, India. The SiO 2 content (48.05 wt% to 65.09 wt% and 35.92 wt% to 50.11 wt% in the bituminous and anthracite samples, respectively) and the ratio of Al 2 O 3 /TiO 2 (6.97 to 17.03 in the bituminous coal samples and 10.34 to 20.07 in the anthracite samples) reveal the intermediate igneous source rock composition of the minerals. The ratio of the K 2 O/Al 2 O 3 in the ash yield of the bituminous coal samples (0.03 to 0.09) may suggest the presence of kaolinite mixed with montmorillonite, while its range in the ash yield of the anthracite samples (0.16 to 0.27) may imply the presence of illite mixed with kaolinite. The chemical index of alteration values may suggest the moderate to strong chemical weathering of the source rock under sub-humid to humid climatic conditions. The plot of the bituminous coal samples in the A–CN–K diagram depicts the traditional weathering trend of parent rocks, but the anthracite samples plot near the illite field and are a bit offset from the weathering trend. This may imply the plausible influences of the potassium-metasomatism at post coalification stages, which is further supported by high K 2 O/Na 2 O ratio (29.88–80.13). The Fourier transform infrared spectra further reveal the hydroxyl stretching intensity of illite in the anthracite samples substantiating the effect of the epigenetic potassium-metasomatism. The decrease in total kaolinite intensity/compound intensity of quartz and feldspar may provide additional evidence towards this epigenetic event.
Evaluating a software design is an important practice of expert software designers. They spend significant time evaluating their solution, by developing an integrated mental model of the software design and the requirements. However, sufficient emphasis has not been given on teaching and learning of evaluation practices in software design courses, and hence, graduating students find it difficult to critically analyse an existing design and improve upon it. In this paper, we describe a model-based learning pedagogy for teaching–learning of software design evaluation. Model-based learning has been extensively used in science education and entails helping students construct, refine, revise, evaluate, and validate scientific models. We argue that modelling practices in software design evaluation are analogous to these practices. We adapted the model-based learning paradigm and operationalised it into a technology-enhanced learning environment (TELE) for fostering software design evaluation skills in computer science undergraduates. We conducted a research study with 22 undergraduate students to explore how the TELE and its features help students effectively evaluate a given software design. Students attempted a pre-test and post-test which asked them to identify defects in the design. We used the content analysis method to identify categories of defects from student responses in the pre-test and post-test. We also analysed student interaction logs and conducted focus group interviews to identify how features in the TELE contributed towards student learning. Findings from the study showed that students’ understanding of evaluation improved, from merely adding new functionalities and requirements, to a process which involved identifying alternate scenarios in the design which violate the given requirements. Students perceived that pedagogical features of the TELE were useful in helping them effectively evaluate software designs. Findings from the study provide evidence for the model-based learning paradigm as an appropriate pedagogy for software design and also opens the space for researchers to investigate model-based learning in other aspects of software design, such as designs of different types and varying complexities.
The effects of landuse/landcover (LULC) and climate change on hydrology and soil erosion processes are of major concern, especially in the humid tropics. In this study, an evaluation of these changes is performed in a humid tropical catchment (Vamanapuram river basin, India) using a physically based distributed model, SHETRAN. The past landuse maps and climate data from six fine resolution NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) are used to force the SHETRAN model. A comparison of the change in the rate of soil erosion and hydrological responses during the future climate scenarios (near: 2021–2050 and far: 2071–2100) with respect to the historical period (1980–2005) is conducted. The isolated effects of landuse, climate variability and the combined effect caused change in streamflow (1.1%, 7.9%, 9.0% respectively) and sediment load (−10.4%, 1.7%, −10.5% respectively) in the past. An ensemble mean of general circulation model (GCM) projections showed that mean temperature and average annual precipitation under representative concentration pathway RCP 4.5 (8.5) scenarios for near and far futures increased from the historic period by 0.51 °C (1.6 °C), 0.6 °C (3.2 °C) and by 9% (6%), 15% (22.8%), respectively. Under RCP4.5(8.5), the average annual streamflow increased gradually from the near to far future, by 3.2% (−1.8%) and 13.6 % (22.1%) whereas, the projected sediment load a showed change of −21.05% (−26.63%) in near future while far future indicated change by −11% (4%). The SHETRAN model has been found to be effective in evaluating climate change impacts on hydrology and sediment yield and is useful for future river basin management.
Due to its significant expansion as a sustainable energy source, the investigation of thin-film-based solar cells is a very important field of research among materials scientists. Nowadays, CdTe based photovoltaic devices are developed using indium sulfide (In2S3) as potential material. This study reports the effect of the annealing temperature, up to 450 °C, on In2S3 physical properties, and the consequences for the use of the In2S3 in photovoltaic devices. Structural analysis on indium sulfide pellets, made from commercial indium sulfide powder, reveals that all the samples are polycrystalline, crystallizing in the tetragonal structure (β phase). Above the annealing temperature of 400 °C, indium oxide (In2O3) is also detected. Optical absorption, in the visible and near-infrared region, is close to zero for all the samples (as-prepared and annealed). The measured band gap energy decreases with annealing temperature up to 350 °C, and increases above this temperature. The conductance of the samples increases with increasing measured temperature, confirming the semiconductor behavior. This work provides an example of the potential application of β-In2S3, in the powder form, for environmental rehabilitation.
The formulation of effective gasoline surrogates is a challenging task due to advanced combustion strategies, engine design and variable operating conditions in spark-ignition engines. In earlier studies, the gasoline surrogates with iso-octane, n-heptane and toluene blends were designed to closely match the commercial gasoline fuels based on their laminar burning velocity variation and ignition delay time measurements. A new approach of proposing the next generation gasoline surrogates is investigated in the present study with direct testing of these surrogates in a real SI engine. The present study helps in assessing the efficacy of proposed gasoline surrogates in a real engine. The combustion, performance, and emission characteristics of proposed gasoline surrogates are compared with the commercially available gasoline fuels. A total of 10 (named A to F) surrogates were investigated with variable percentage of iso-octane, n-heptane and toluene. All the tested surrogates were successfully tested in a multi-cylinder engine. The result shows that, SF and SG are suitable to reproduce the combustion and emission characteristics of commercially available gasolines during detailed engine testing. It is observed that surrogate F and G results are more aligned with the commercial gasoline fuels thus representing the commercial gasoline more closely and can use further for validation and modeling of IC engines through the application of detailed kinetic models. However, a significant change was observed for other tested surrogates.
The present numerical study characterizes nucleate boiling heat transfer in ethanol from a single nucleation site on a horizontal base plate in the presence of a fluid-immersed solid copper torus. The torus lies above the base plate, with its axis centered along the nucleation site, and it is either kept stationary or subjected to forced oscillations in the vertical direction. A sharp-interface dual grid Level Set method (SI-DGLSM)-based in-house solver is used here, in which a Level Set-based Immersed Boundary Method (LSIBM) is used to impose the boundary condition at the moving solid-fluid interfaces. For nucleate boiling in the presence of a stationary torus, enhancement in Nusselt number is observed due to thinning of the thermal boundary layer under the torus and thickening of the thermal boundary layer near the bubble. In the presence of torus oscillations, a lock-on regime is observed at optimal actuation parameters, for which the frequency of bubble departure synchronizes with the actuation frequency of the torus. A significant increase in Nusselt number is observed within the lock-on regime due to active pumping of superheated liquid towards the nucleating bubble during bubble growth. Analysis of heat flux partitioning shows that the enhancement in Nusselt number may be mainly attributed to higher sensible heat flux in the presence of torus oscillations, especially near the lock-on regime. This work demonstrates a novel way for enhancing heat transfer in the single-bubble nucleate boiling regime via externally actuated solid objects immersed in the liquid.
Engineering the van-der-Waals gap by interlayer water confinement and hydration enable superfast ions transfer and intercalation that boosts the charge storage performance. Herein, we report the van-der-Waals gap modification into the layered WO3 nanostructures using cost-effective wet chemical method. The larger water molecules insertion into the hydrated WO3 crystal structure facilitates the expansion of van-der-Waals gap, which results the improvement of nanoplates thickness. The electrochemical performance in the thicker hydrated WO3 nanoplates is enhanced owing to the better crystalline nature and electrical conductivity along with van-der-Waals gap modification. Hence, the significant boost of single electrode specific capacitance from 160 F g⁻¹ to 250 F g⁻¹ at 2 mV s⁻¹ is observed in 1 M H2SO4 aqueous electrolyte. Further an asymmetric supercapacitor of 1.6 V exhibits the capacitance value 27 F g⁻¹ at 1 A g⁻¹ with 8000 Wh kg⁻¹ power density and 87% capacitance retention after 2500 cycles. The van-der-Waal gaps engineering of layered materials is a potential strategy to amplify supercapacitor performance.
In situ laser energy deposition ahead of supersonic/hypersonic vehicles controls the surface force and reduces drag dramatically. In the present study, the effects of repetitive laser pulse deposition on the flow-field alteration and wave drag reduction over a blunt body travelling at supersonic speed are investigated. The simulation is performed by solving the Navier-Stokes equation accompanied by the species conservation equations in two dimensions by assuming chemical non-equilibrium and thermal equilibrium. The interaction of the low-density area (of the breakdown induced by blast-wave) and the bow shock in front of the body, results in modification in the flow-field, thereby reducing the wave drag. The maximum drag reduction occurs when the repetition rate is kept below 100 kHz for all the positions of energy deposition considered in the present study. Higher frequencies of energy deposition result in higher wave drag on the body. For 300 kHz and the farthest location considered in the present study, the drag reduction is found as low as 18% of drag without energy deposition with 6.8% aerodynamic efficiency. The maximum wave drag reduction was observed at 50 kHz with a maximum aerodynamic efficiency of 78.7% at the farthest position of energy deposition considered in the present study.
Despite significant progress in the solution of Neutron Transport Equation (NTE) using Lattice Boltzmann Method (LBM), it suffers from the ray effect a problem similar to SN methods. The ray effect is prominent in the problems where source is localized and medium has low scattering cross-section. Due to ray effect spatial distortion in the scalar flux and angular flux is observed. This effect arises because NTE is solved in discrete directions, allowing neutrons to travel only in a few directions. Therefore, first collision source (FCS) method is applied for SN method. Presently, FCS method is applied to LBM and result are obtained for two-dimensional source problems. It is observed that by applying FCS to LBM, ray effect is mitigated. Compared to SN method, LBM approach is relatively simple in implementation and can be effectively used. Therefore, it has potential to provide easy and convenient solution of neutron transport equation.
With the ever-increasing size of anaerobic digesters (AD), the management and disposal of digestate have become a challenging task for AD operators. Anaerobic digestate is rich in nutrients and contaminants; thus, a suitable treatment is required to meet environmental legislation and protect the receiving environment. There has been a thrust among the research efforts in anaerobic digestate management in the last decade. Volarization of digestate into high-value products is necessary to make the AD process more cost-effective. Moreover, digestate utilization helps in recycling the already mined resources. Efforts have been made to use digestate as a feedstock to recover energy and value-added products such as nutrients (N, P), biochar, biofuels, polyhydroxyalkanoates (PHAs), and algal cultivation, which can arguably help to enable the circular economy in modern communities. This communication thoroughly examines the anaerobic digestate-based biorefinery concept and its linkages with the circular bio-economy. This review comprehensively summarized digestate management practices; recovery of renewable fuels and other value-added products from digestate, including bottlenecks and perspectives altogether in digestate management and treatment. The state-of-the-art of commercialization of anaerobic digestate valorization technologies has also been provided. Overall, this review could support decision-makers in identifying environmentally sound and sustainable solutions ahead of time.
The utilization of landfill-mined-soil-like fractions (LFMSF), which is a major fraction resulting from landfill mining (LFM) activity, is being debated owing to a lack of comprehensive understanding of its characteristics. In this context, based on the physicochemical properties of LFMSF, several of the earlier researchers have opposed its utilization as compost, feedstock in waste-to-energy applications, and fill material in civil engineering applications. However, it has been noticed that LFMSF consists of enough amount of organic matter (OM) and inorganic carbon (IC) to make it suitable as a buffering material that would help to modify/treat geomaterials exhibiting extreme pH values. In this context, the determination of its buffering capacity (BC), a parameter that quantifies the buffering potential, becomes essential. However, determination of BC by resorting to the existing protocols is not suggestible mainly due to (i) an extremely narrow range of the pH (3–8) employed, (ii) lack of incorporation of the optimal time required for reaction/pH stabilization (tpHS), (iii) concern for decomposition of OM during the addition of H⁺/OH⁻ while experimentation and (iv) heterogeneity associated with the LFMSF unlike the geomaterials that are commonly tested (viz., agricultural soils and compost). Hence, to overcome these limitations, a comprehensive methodology that can be employed for determining the ultimate buffering capacity (BCu) by establishing appropriate tpHS (i.e., 200 h) and liquid to solid ratio (i.e., 20), which would eliminate the decomposition of OM over a broad range of pH (i.e., 2–12) has been proposed. Based on the testing of several LFMSF samples collected from various landfill/dumpsites in India, easy-to-use relationships between the (i) reaction time (t) and (ii) physicochemical properties of the samples that influence BC and BCu, directly or indirectly, have also been proposed.
The storm surge and hydrodynamics along the Krishna–Godavari (K–G) basin are examined based on numerical experiments designed from assessing the landfalling cyclones in Bay of Bengal (BoB) over the past 38 years with respect to its highest maximum sustained wind speed and its duration. The model is validated with the observed water levels at the tide gauge stations at Visakhapatnam during 2013 Helen and 2014Hudhud. Effect of gradual and rapid intensification of cyclones on the peak water levels and depth average currents are examined and the vulnerable locations are identified. The duration of intensification of a rapidly intensifying cyclone over the continental shelf contributed to about 10–18% increase in the peak water levels, whereas for the gradually intensifying cyclone the effect is trivial. The inclusion of the wave-setup increased the peak water levels up to 39% compared to those without wave-setup. In the deep water region, only rapidly intensifying cyclones affected the peak MWEs. Intensification over the continental slope region significantly increases the currents along the shelf region and coast. The effect on peak maximum depth averaged current extends up to 400 km from the landfall location. Thus, it is necessary to consider the effect of various combinations of the highest cyclone intensity and duration of intensification for identifying the worst scenarios for impact assessment of coastal processes and sediment transport. The study is quite useful in improving the storm surge prediction, in preparedness, risk evaluation, and vulnerability assessment of the coastal regions in the present changing climate.
To run a sustainable society, hydrogen is considered as one of the most reliable option for clean and carbon free energy carrier. Hydrogen can be produced through several means using renewable energy sources, and can be stored either in solid, liquid or gaseous state. Though, compressed and liquefied hydrogen storages are well-established technologies in the commercial sector, however, due to the leakage risk, boil-off losses and explosive nature, world is exploring a safer way of hydrogen storage i.e. absorption/adsorption based solid-state hydrogen storage technology. The present review focuses mainly on the different material options available for the absorption based solid state hydrogen storage technology. The study reports insight view of different absorption material, broadly classified as metal hydrides and complex hydrides, with their hydrogen storage and reversible characteristics. The review also reports the tailoring properties of different hydrogen storage alloys and effect of element substitution on the absorption/desorption characteristics of a particular alloy. Key issues like effect of ball milling, annealing, doping, grain size, etc., on the alloy synthesis have been addressed. The review broadly summarizes the progress and recent worldwide advancement in the absorption based solid state hydrogen storage materials, synthesis and their hydrogenation/dehydrogenation mechanisms.
Solar selective absorber coatings with wide angular solar absorptance aids in attaining high photo-thermal conversion efficiency for solar thermal systems. In this regard, nanoparticles-based absorber coatings were developed on stainless steel grade 304 by combining the impregnation method, solvothermal process, and dip-coating technique. Developed nanocomposite (SiO2 nanoparticles in transition metal oxide matrix) based single layer absorber coating with nano void textured surface, exhibits solar absorptance of 0.92 and spectral emittance of 0.12. MgF2 nanoparticles based anti-reflective layer on single-layer absorber coating improves the solar absorptance to 0.94 by destructive interference mechanism. Both nanoparticles based single and tandem absorber coatings show wide angular solar absorptance of 0.88 and 0.89, respectively, at an incidence angle of 50°. Besides, developed absorber coatings show lower thermal emissivity of 0.17 and good photo-thermal conversion efficiencies at high operating temperatures (400–500 °C). These developed absorber coatings offer excellent thermal stability at an open atmospheric condition till operating temperature, such as 400 °C for 100 h. Selective nature with wide angular solar absorptance and low heat loss behaviour of stable absorber coating show the photo-thermal conversion efficiency of 91% can improve the performance of receiver tubes in solar thermal systems.
A broadband coplanar waveguide fed butterfly shape slot antenna is presented in this paper. The designed antenna operates in the frequency range from 1.89 to 5.21 GHz (93.5%) for S11 ≤ −10 dB with a broadside gain of 5 ± 1 dBi over the bandwidth of 1.97–5.19 GHz (90.3%). The designed antenna is uniplanar having the size of 0.5 λ0 × 0.28 λ0 × 0.005 λ0 (λ0 is the wavelength at the lowest operating frequency in free space). The proposed configuration has a stable radiation pattern over the operating frequency band. The designed antenna is fabricated and simulated results are validated with measured results.
This review presents the current status of solar air heating systems in various sectors and industries and its prospect of integration with existing drying methods. Most of published review articles in this domain have focused on the use of solar drying in agricultural industries for food preservation. Many researchers have identified component level gaps and proposed various changes to solar thermal collectors for improved drying performance. Various technologies have been developed and implemented which optimised the energy requirements effectively and efficiently. However, there have been very few studies focusing on the potential integration methods in various industries where drying is an essential process during production. In this paper, a detailed review of the essential drying processes in various industries is presented to provide a perspective on the current state of available technologies and the ongoing research in the field solar drying. In addition to the agricultural industry, the paper also discusses the potential use of this technology in other emerging areas. Few industrial installations of this technology have been reviewed, and the major findings and observations have been reported. Possible integration of solar drying with the existing drying methods has been proposed to create novel drying systems for large-scale industries that can be generalised for industrial applications. Solar based drying technology can help in reducing the energy consumption of conventional dryers up to 15% to 80%, which could in turn reduce the carbon dioxide emissions annually by 20% to 80%, depending on the type of the industry and the material or product to be dried. This review will assist researchers and industries in making the drying process compatible with solar energy.
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15,946 members
Chintan Modi
  • Department of Systems and Control Engineering
Rashmi Gupta
  • Department of Humanities & Social Sciences
Rajesh Kancherla
  • Department of Chemistry
Rajneesh Mishra
  • Department of Metallurgical Engineering & Materials Science Including Corrosion Science & Engineering
A.K. Suresh
  • Department of Chemical Engineering
Powai, 400076, Mumbai, Maharashtra, India
Head of institution
Prof. Subhasis Chaudhuri, Director