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- PublicationCyclic Behaviour of Pond Ash-Based Controlled Low Strength Material(01-01-2020)
;Dev, K. LiniFlowable fills, also called as Controlled Low Strength Materials (CLSM), are often used as alternative to compacted granular materials in specific situations like bedding layer to buried pipelines and backfill behind retaining walls. The fills are widely used in places where compaction cannot be done due to inaccessibility for moving compaction equipment and are often subjected to cyclic loading. While several studies are available in the literature on the static behaviour of flowable fills, the cyclic behaviour of flowable fills received less attention. This paper focuses on the cyclic behaviour of pond ash-based flowable fills. Comparative studies were carried out on compacted pond ash (CPA) specimens prepared at both standard and modified Proctor unit weight and optimum moisture content for similar testing conditions. The cyclic behaviour was studied by performing cyclic triaxial tests for different cyclic stress ratio (CSR) on both compacted pond ash and flowable fill. The results obtained based on cyclic triaxial tests showed that the flowable fills perform much better compared to the compacted pond ash specimens. - PublicationAn area efficient, high-resolution fully foldable switched-capacitor DC-DC converter with 16% efficiency improvement(01-01-2020)
;Peetala, Kishore ;Ranjan, Adibya ;Ankamreddi, RamakrishnaA Fully foldable modified Dickson architecture (FFMDA) based switched-capacitor dc-dc converter is proposed in this paper. The proposed converter uses only 4-stages in contrast to 5-stages in a regular Foldable Dickson converter to achieve the same number of gain settings, thereby becomes 20% area efficient. Peak efficiency improvement of 16% is achieved with a fully-foldable nature of proposed architecture in combination with subtraction mode. The converter is implemented in 130nm technology and uses stacked MOS and MIM capacitors to get the highest density. Operating at 2V input, the converter provides a wide range of regulated output voltages from 0.2 to 1.28V and delivers load current from 100µA to 2mA with average and peak efficiency of 71.35% and 87.5%, respectively. - PublicationProtein folding: how, why, and beyond(01-01-2020)Identifying the series of molecular events that take place when a protein molecule folds or unfolds has confounded and delighted researchers alike while challenging the limits of experimental approaches and the applicability of theoretical models and simulations. This chapter discusses the vast conformational space accessible to a protein chain, the diversity of weak noncovalent interactions it makes, the role of solvent compensating energetic-entropic terms, and the cellular environment, all of which weave an intricate fabric of complexity during the folding of a protein. Emphasis is placed on how generating conformational landscapes in a quantitative fashion can provide an unparalleled view of competing substates, which can either aid in or hinder folding, thus playing a role in function and disease. The role and effect of mutations, the drivers of evolution, are discussed in detail along with the current high pedestal of disordered proteins that has overturned the conventional structure-function paradigm.
- PublicationEvaluation of sizing strategies for eVTOL UAV configurations(01-01-2020)
;Sridharan, AnantheVTOL sizing is tackled with a Multi-Disciplinary Optimization problem with nonlinear constraints in this work, focusing on UAVs with distributed vertical lift. Several optimization schemes are investigated for including airframe sizing with finite element analysis, vehicle trim, and blade aerodynamic shape design. The iterative weight convergence loop is replaced by a slack variable and equality constraint for the sizing optimizer. Airframe sizing and weight minimization (with stress inequality constraints) may be driven either by the sizing optimizer, or by a separate optimizer within the various constraint functions in a nested structure. It is preferable to drive the trim variables using the sizing optimizer; if a particular design cannot be trimmed, this information is propagated to the sizing optimizer through the corresponding equality constraints. The all-at-once optimization strategy yields results in the shortest time compared to the other methods. Using modified momentum theory for rotor performance, all gradient-based optimizations from different starting points converged to the same minimum, indicating that the design space is convex for the chosen bounds and objective function. Blade shape design with BEMT is also included in the sizing, either directly with blade twist and taper as additional design variables, or indirectly through a response surface. The methodology is demonstrated on the sizing of two package delivery vehicle configurations (a quadrotor and a lift-augment quadrotor biplane tailsitter) for a mission with 10 km radius of action. The cruise airspeeds for the two configurations are also identified as part of the sizing/optimization. The quadrotor is more suited for this point mission owing to its lower empty weight compared to the quad-biplane, which has better cruise efficiency but higher empty weight. - PublicationEMPIR: ENSEMBLES OF MIXED PRECISION DEEP NETWORKS FOR INCREASED ROBUSTNESS AGAINST ADVERSARIAL ATTACKS(01-01-2020)
;Sen, Sanchari ;Ravindran, BalaramanRaghunathan, AnandEnsuring robustness of Deep Neural Networks (DNNs) is crucial to their adoption in safety-critical applications such as self-driving cars, drones, and healthcare. Notably, DNNs are vulnerable to adversarial attacks in which small input perturbations can produce catastrophic misclassifications. In this work, we propose EMPIR, ensembles of quantized DNN models with different numerical precisions, as a new approach to increase robustness against adversarial attacks. EMPIR is based on the observation that quantized neural networks often demonstrate much higher robustness to adversarial attacks than full precision networks, but at the cost of a substantial loss in accuracy on the original (unperturbed) inputs. EMPIR overcomes this limitation to achieve the “best of both worlds”, i.e., the higher unperturbed accuracies of the full precision models combined with the higher robustness of the low precision models, by composing them in an ensemble. Further, as low precision DNN models have significantly lower computational and storage requirements than full precision models, EMPIR models only incur modest compute and memory overheads compared to a single full-precision model (<25% in our evaluations). We evaluate EMPIR across a suite of DNNs for 3 different image recognition tasks (MNIST, CIFAR-10 and ImageNet) and under 4 different adversarial attacks. Our results indicate that EMPIR boosts the average adversarial accuracies by 42.6%, 15.2% and 10.5% for the DNN models trained on the MNIST, CIFAR-10 and ImageNet datasets respectively, when compared to single full-precision models, without sacrificing accuracy on the unperturbed inputs. - PublicationIntroduction(01-01-2020)
;Krishnan, SubramaniamRaghavan, JeenuA brief introduction to the components of a typical solid propellant rocket motor is given. The division of the pressure-time trace of solid motor into ignition transient, equilibrium operation, and tail-off transient is explained. Next, the two basic methods of performance prediction, namely equilibrium-pressure analysis and incremental analysis, are introduced and their applicability conditions based on port-to-throat area ratios and volumetric loading fractions of propellant are discussed. - PublicationScalable synthesis of two-dimensional metal organic frameworks and insights into solvent-guided oriented attachment(01-01-2020)
;Jose, Nicholas A.; ;Mushrif, Samir H. ;Zeng, Hua ChunLapkin, Alexei A.Two-dimensional metal organic frameworks (2D MOFs) are a class of next generation materials for adsorbents,membranes and sensors; however, many 2D MOF synthesis methods lack the scalability and precision required for translation to industrial scales. Furthermore, the engineering of 2D MOF structures is challenged by complex environment-surface interactions that arise from their high anisotropy, thinness and functionally diverse surfaces. In this work we developed new understandings and methods of engineering such structures by using accelerated, high shear synthesis, and solvent exchange. With the recently developed annular flow microreactor we synthesized 2DMOFs more efficiently than conventional batch methods, by up to 5 orders of magnitude in terms of reactor space-time-yield. To accurately characterize particle size and dynamics in various organic solvents, we used liquid cell transmission electron microscopy. This technique not only visualized the oriented attachment of nanosheets, but also showed that the rate and direction of attachment is significantly influenced by solvent-surface interactions. These techniques and understandings provide rational bases for 2D MOF engineering and process design. - PublicationA droplet-based detection and sorting of cells utilizing optofluidics and electro-coalescence technique(01-01-2020)
;Gaikwad, RavindraWe demonstrated the detection and isolation of fluorescently tagged cancer cells (HeLa and DU145) from a mixed population of cells and peripheral blood mononuclear cells at a concentration range ͳͲ4-ͳͲ6 at 300 cells per second in a single-cell droplet format. Initially, cells are focused in the single-file stream using sheath fluid before getting encapsulated in the droplets at the droplet junction. The cell encapsulated droplet then analysed and characterised based on different scatter and fluorescent signals at the optical detection zone. The fluorescent signals from the target cells activate a selective electro-coalescence isolation module which uses a very low voltage (60V). - PublicationSustainability practices in tourism supply chain with confirmatory factor analysis(01-01-2020)
;Babu, Deepak EldhoThe purpose of the research paper is to provide insight to the Indian hotel administrators by identifying key sustainability practices that can be jointly adopted with their supply chain members and will effectively contribute to the management of hospitality operations. A comprehensive framework is developed and a confirmatory factor analysis is used to test the relationship between the observed indicators and their factors. A set of reliable and valid measurements of sustainability practices in tourism supply chain that aims at the betterment of hospitality management methods is an outcome of the paper. The identified sustainability practices are used for conceptualisation of the model which can be logically used by the practicing managers in tourism supply chain and gain competitive advantage. The findings clearly suggest that sustainability practices need to be looked from the supply chain perspective than as individually. - PublicationInjection locking in switching power amplifiers(01-01-2020)
;Mishra, Amit Kumar; Shekhar, SudipIn this work, injection locking in switching power amplifiers (PAs) is studied. Traditionally, injection-locked PAs (ILPAs) have supported phase modulation, with injection locking used primarily to improve the power-added efficiency by reducing the power required to drive the ILPA. Since the output power in conventional ILPA architectures is mainly contributed by the locked oscillator in an ILPA, the amplitude modulation is difficult to achieve unless supply modulation is employed. In the ILPA presented in this work, it is shown that by injection locking a switching PA and a power oscillator, improvement in both power-added efficiency and drain efficiency can be achieved as compared to just a switching PA. Moreover, amplitude modulation at a fixed supply voltage is achieved using an RF-DAC approach to scale both the switching PA and the locked oscillator. This approach employs variable injection-strengths varying from ≤1 (weak injection locking) to >1 (strong injection locking) to achieve the required power back-off. Accordingly, new formulations are introduced to extend the existing injection locking theory for injection strengths >1 case in ILPAs. Benefits of a larger injection strength on lock-range, maximum allowable symbol rate, AM-PM distortion and phase noise performance for an ILPA is provided. An ILPA is designed to support 64-QAM and implemented in a standard 65-nm bulk CMOS process. A peak drain efficiency of 42.7% and power-added efficiency of 40% is measured at the highest output power of 23 dBm, operating from a 1.45 V PA power supply at 2.5 GHz. Modulation tests with 5/50 MSym/s 64-QAM signals achieve the measured RMS EVM of 1.9%/3.1% with the average output power, drain efficiency and power-added efficiency of 18.1 dBm, 27.9% and 25.8% at 2.5 GHz, respectively. - PublicationCarbo-click in drug discovery and development: Opportunities and challenges(01-01-2020)
;Kushwaha, Divya ;Singh, Sumit K.Tiwari, Vinod KumarCu(I)-Catalyzed click reaction of organic azide and terminal alkyne has been identified as one of the most facile and reliable strategy for the ready construction of diversely functionalized molecules. This highly efficient protocol regioselectively produces 1, 4-disubstituted 1, 2, 3-triazole under mild reaction conditions, which is well known heterocycle for its pharmacological properties. The compatibility of click reaction with carbohydrates has enabled the synthesis of diverse glycoconjugates and thus, speeded up the process of drug discovery and development in the area of glycoscience. This chapter surveys the recent applications of click chemistry in the development of carbohydrate-based therapeutics. - PublicationChanging poverty line - inclusion and exclusion of poor in Indian states(01-01-2020)Murugesan, BalajiThe Tendulkar committee and the Rangarajan committee had provided different poverty estimates for India in the past. It is necessary to appreciate the consequences of changing poverty estimates in identification of poor and non-poor households. This paper seeks to examine the sensitivity of the distributional profile in eight developed and under developed Indian states to a unit change in Tendulkar poverty line by applying kernel density function for the consumer expenditure distribution from the National Sample Survey Organization's 55th, 61st, 66th and 68th quinquennial rounds. The developed states have exhibited higher sensitivity compared to neo-patrimonial states to a unit change in poverty line. It is ascertained that the inclusion error will decline and exclusion error will increase if we move down the poverty line over a period of time as the poor people in the poverty zone are escaping at varied rates across space and time.
- PublicationIntegration of Geddesian Town Planning Theory into Marketing: An Interdisciplinary Approach for Bottom of Pyramid Market: An Abstract(01-01-2020)
;Chaudhary, AyushUntil recently, the Bottom of Pyramid market was largely ignored by the multinationals, due to huge challenges it possesses to overcome; but now an increasing number of multinationals are trying to tap this huge and lucrative market. Most of the attempts of multinationals are resulting into partial success or no success at all. On the other side, many academicians have criticized this approach on the grounds of vulnerability of its consumers, market size and sustainable profits for MNC’s. Thus, there is an urgent need to build a robust theoretical framework that will help in not only overcoming the criticism laid by the various academicians but also will help in understanding the dynamics of this huge lucrative yet challenging market. This study aims to address this lacuna, by developing a theoretical framework with completely new perspective, which is, borrowed from a different discipline of literature – Town Planning. The Geddesian Theory of town planning has its roots deeply anchored in three different disciplines of Biology, Sociology and Social Sciences. The Biological perspective is based on Darwin’s theory of triumvirate of Organism, Function and Environment. The Sociological perspective is based on Le Play’s understanding of social structure of society and the Social Science perspective is based upon Geography, Economics and Anthropology, the three contemporary components of Social Science. Geddesian Town planning theory is one of the oldest and widely known theory of town planning. The uniqueness of Geddes theory is that it keeps the people or what Geddes popularly call them as Folk at the centre stage. Both, Geddes Town planning theory and Bottom of Pyramid literature are common in terms of their focus on vulnerability of people, focus on being people centric. Moreover, both the theory and practice are considerate about employment opportunity and the economic aspect of people. The three main tenants of Geddesian Theory – Folk, Work and Place are reflected as Consumer, Propensity to consume, and Place in this new framework. The purpose of this research is twofold, firstly to draw parity between Geddesian Town planning theory and Bottom of the Pyramid market and secondly to develop a new framework, which will help in understanding this market from a fresh perspective. - PublicationMicromechanics based analytical model for estimation of stress distribution and failure initiation in constituents of UDFRP composites subjected to transverse loading(01-01-2020)
;Verma, Akash; ;Akella, KiranSivakumar, Srinivasan M.When a Unidirectional fiber reinforced polymer (UDFRP) composite is subjected to transverse loading, there is spatial variation of stresses in the constituents. The failure in matrix initiates at the location of maximum stress. Stress distribution and failure initiation in constituents of UDFRP composites is usually studied through finite element (FE) analysis of representative volume element (RVE) which is computationally expensive and time consuming. The present study proposes an analytical model through which stress variation and failure initiation in the constituents of UDFRP composite can be obtained in simple and reliable way and it can be readily used in designing. For this model, RVE is idealized in the form of springs arranged in parallel and series. These springs represent the stiffness of constituents (fiber and matrix). The results of analytical model are compared with FE simulations and good agreement is observed. Influence of fiber volume fraction on failure initiation of UDFRP composites is also studied through FE analysis of RVE and analytical model. - PublicationCFD analysis of the HTGR reactor response to depressurization accidents(01-01-2020)
;Srinivasan, NavnccthRcvankar, Shripad T. - PublicationA Lagrangian-relaxation-based bounding approach for the convoy movement problem in military logistics(01-01-2020)
;Ezhil, S. A.Convoy movement problem (CMP) is an important optimisation problem, especially occurring in military logistics, which focuses on routing convoys concurrently in a network. The CMP is subject to constraints for preventing certain interactions between convoys such that the objectives related to travel times of them are minimised. We propose a Lagrangian relaxation (LR) approach to efficiently obtain a lower bound on the optimal solution. Our LR approach does not have integrality property, and hence the lower bound obtained is always tigher than the lower bound obtained using the LP relaxation. As CMP is an NP-complete problem, lower bounds are useful to evaluate the solutions obtained by a heuristic. From our computational experimentation, it is found that the proposed LR approach is superior to the existing LR approach. - PublicationComplexities of Natural Gas Hydrates as an Energy Resource and its relation with Climate Change(01-01-2020)The ever-growing energy demands, declining oil prices, dwindling new findings of oil/gas reservoirs, complexity, and uncertainty associated with unconventional oil/gas supplies; and the seriousness towards mitigating the greenhouse gas emissions essentially implies the risky and uncertain nature of future energy at the global scale. Such a risky and complex pathway has made the exploration of unconventional hydrocarbons resources such as natural gas hydrates one of the potential alternatives that can significantly contribute to the growing energy demand. There is a huge gap between the experimental investigations and its associated up-scaling to a larger field-scale as these gas hydrates are generally located in highly remote places such as polar- and marine-environments. Thus, more studies are still required towards the field-scale exploration and production of gas-hydrates with their associated environmental, economic, and social consequences. In this context, an attempt has been made in order to list out the practical difficulties that are experienced during the exploration and production of natural gas hydrates as a possible and new energy resource given the constraints associated with the conventional fossil fuels. These complexities associated with the real field-scale production of gas hydrates are expected to provide improved insights for experimental scientists working on gas hydrates. In addition, the way the natural gas hydrates gets associated with climate change has been discussed in detail, and critical conclusions have been drawn.
- PublicationPlatinum-based anode catalyst systems for direct methanol fuel cells(01-01-2020)Viswanathan, B.Direct methanol fuel cell may become a practical device sooner or later. For effective utilization of this device for energy conversion the anode reaction has to be promoted efficiently and economically. Among the various anode catalysts tried, Pt-based systems have shown some promise and Pt in combination with other metals are examined in order to overcome the poisoning effect of partially oxidized product, such as Co or –CHO species. The limitations in this technology, namely, carbon corrosion, Ru dissolution, and crossover, in addition to methanol crossover, have to be overcome to make this a commercially viable technology. The prospects of this technology are also outlined.
- PublicationErratum to “Thermodynamics and folding landscapes of large proteins from a statistical mechanical model†[Current Research in Structural Biology 1 (2019) 6–12] (Current Research in Structural Biology (2019) 1 (6–12), (S2665928X19300030), (10.1016/j.crstbi.2019.10.002))(01-01-2020)
;Gopi, Soundhararajan ;Aranganathan, AkashnathanThe Publisher regrets that the “Conflict of Interest” statement was not included in the published article at the time of publication. The Authors confirm that they do not have any Conflict of interest to report for this article. The Publisher would like to apologise for any inconvenience caused. - PublicationERLP: Ensembles of Reinforcement Learning Policies(01-01-2020)
;Saphal, Rohan ;Ravindran, Balaraman ;Mudigere, Dheevatsa ;Avancha, SasikanthKaul, BharatReinforcement learning algorithms are sensitive to hyperparameters and require tuning and tweaking for specific environments for improving performance. Ensembles of reinforcement learning models on the other hand are known to be much more robust and stable. However, training multiple models independently on an environment suffers from high sample complexity. We present here a methodology to create multiple models from a single training instance that can be used in an ensemble through directed perturbation of the model parameters at regular intervals. This allows training a single model that converges to several local minima during the optimization process as a result of the perturbation. By saving the model parameters at each such instance, we obtain multiple policies during training that are ensembled during evaluation.We evaluate our approach on challenging discrete and continuous control tasks and also discuss various ensembling strategies. Our framework is substantially sample efficient, computationally inexpensive and is seen to outperform state of the art (SOTA) approaches.