Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

&nbsp;

IIT Palakkad

This paper presents the mathematical design and implementation of an actuator fault-tolerant control system for an underwater robot having four rotatable thrusters where the rotatable action of the thrusters is unconventional to a conventional underwater robotic system. Initially, the dynamic model of the robot is presented. Later, a motion control scheme using a backstepping control technique is made to track a desired spatial trajectory. Two techniques of active fault tolerance control viz., Elimination of Column Method, and Weighted-Pseudo Inverse Method are implemented successfully for single actuator faults on an infinity-shaped trajectory, which is a critical aspect of this study as most of the previous literature reported only on set point control. The methods mentioned above are extended to multiple thrusters failure, but both of them could not handle more than a single thruster failure. Hence, an attempt is made to accommodate two thrusters' failure through the line of sight approach by considering the vehicle as under-actuated. The desired vehicle performance is achieved with this approach. Finally, oceanic currents are modeled to simulate the effectiveness of the methods discussed in the paper to prove the performance capabilities of the control system and fault accommodation schemes under realistic conditions. © 2020 Elsevier Ltd

World University root node

Department of Mechanical Engineering

Ocean Engineering

Actuator fault-tolerant control study of an underwater robot with four rotatable thrusters

This paper presents a robust motion control of a sitting-type lower limb rehabilitation robot (LLRR) in its operational-space. The mathematical background of the proposed robot is discussed and its motion control design in the task-space based on a double-loop control approach is derived herein along with its closed-loop system stability analysis. The motion tracking performance analysis of the proposed scheme is demonstrated using computer based numerical simulations. For numerical simulations and to validate the effectiveness of the motion control strategy, the clinically obtained test gait data is used for the desired motion trajectory of the lower limb rehabilitation robot. © 2020, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.

Advances in Intelligent Systems and Computing

Robust Operational-Space Motion Control of a Sitting-Type Lower Limb Rehabilitation Robot

Department of Civil Engineering

Annual Meeting- Asia Oceania Geosciences Society (AOGS)

A comparative study on different calibration approaches for streamflow prediction in SWAT Model

Department of Mathematics

Information Geometry

Cram{\'{e}}r–Rao lower bounds arising from generalized Csisz{\'{a}}r divergences

This paper reviews the feasibility of using low grade clay for developing geopolymer mortar by partially replacing conventional source material. The study intends to develop a framework for identification, classification and utilization of various clays and suggest suitable processing techniques to qualify for geopolymerization. The influence of source clay based on the reactivity of silica, physical, chemical and mineralogical characteristics on the properties of geopolymer mortar is extensively studied based on existing literature. Characteristics of clay after various treatment methods (calcining and lime treatment) are also reviewed so as to identify the extent of its effectiveness on geopolymers. Characteristics based on micro-structural studies such as energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD) along with geotechnical characterization are reviewed. The paper highlights the significant characteristics of clay that is significant for geopolymerization and its implication on the properties of geopolymer mortar. The manifestation of geopolymer characteristics and its relation to crystallography and microstructure is explored to develop strategies for the qualification of clays. The influence of parameters such as alkali concentration and sodium silicate to sodium hydroxide ratio on compressive strength is presented. Based on the review, an attempt has been made to characterize different types of clay obtained from few sources in India, and a study has been conducted to assess the qualification technique proposed. © RILEM 2020.

Environmental Sciences and Sustainable Engineering Centre (ESSENCE)

RILEM Bookseries

Qualifying of Low Grade Clay for Geopolymer Mortar: A Preliminary Assessment

We describe a new and simple strategy based on the Gauss divergence theorem for obtaining centroidal gradients on unstructured meshes. Unlike the standard Green–Gauss (SGG) reconstruction which requires face values of quantities whose gradients are sought, the proposed approach reconstructs the gradients using the normal derivative(s) at the faces. The new strategy, referred to as the Modified Green–Gauss (MGG) reconstruction results in consistent gradients which are at least first-order accurate on arbitrary polygonal meshes. We show that the MGG reconstruction is linearity preserving independent of the mesh topology and retains the consistent behaviour of gradients even on meshes with large curvature and high aspect ratios. The gradient accuracy in MGG reconstruction depends on the accuracy of discretisation of the normal derivatives at faces and this necessitates an iterative approach for gradient computation on non-orthogonal meshes. Numerical studies on different mesh topologies demonstrate that MGG reconstruction gives accurate and consistent gradients on non-orthogonal meshes, with the number of iterations proportional to the extent of non-orthogonality. The MGG reconstruction is found to be consistent even on meshes with large aspect ratio and curvature with the errors being lesser than those from linear least-squares reconstruction. A non-iterative strategy in conjunction with MGG reconstruction is proposed for gradient computations in finite volume simulations that achieves the accuracy and robustness of MGG reconstruction at a cost equivalent to that of SGG reconstruction. The efficacy of this strategy for fluid flow problems is demonstrated through numerical investigations in both incompressible and compressible regimes. The MGG reconstruction may, therefore, be viewed as a novel and promising blend of least-squares and Green–Gauss based approaches which can be implemented with little effort in open-source finite-volume solvers and legacy codes. © 2018 Elsevier Inc.

Journal of Computational Physics

A new Green–Gauss reconstruction on unstructured meshes. Part I: Gradient reconstruction

For improved stability of fluid-conveying pipes operating under the thermal environment, functionally graded materials (FGMs) are recommended in a few recent studies. Besides this advantage, the nonlinear dynamics of fluid-conveying FG pipes is an important concern for their engineering applications. The present study is carried out in this direction, where the nonlinear dynamics of a vertical FG pipe conveying hot fluid is studied thoroughly. The FG pipe is considered with pinned ends while the internal hot fluid flows with the steady or pulsatile flow velocity. Based on the Euler–Bernoulli beam theory and the plug-flow model, the nonlinear governing equation of motion of the fluid-conveying FG pipe is derived in the form of the nonlinear integro-partial-differential equation that is subsequently reduced as the nonlinear temporal differential equation using Galerkin method. The solutions in the time or frequency domain are obtained by implementing the adaptive Runge–Kutta method or harmonic balance method. First, the divergence characteristics of the FG pipe are investigated and it is found that buckling of the FG pipe arises mainly because of temperature of the internal fluid. Next, the dynamic characteristics of the FG pipe corresponding to its pre- and post-buckled equilibrium states are studied. In the pre-buckled equilibrium state, higher-order parametric resonances are observed in addition to the principal primary and secondary parametric resonances, and thus the usual shape of the parametric instability region deviates. However, in the post-buckled equilibrium state of the FG pipe, its chaotic oscillations may arise through the intermittent transition route, cyclic-fold bifurcation, period-doubling bifurcation and subcritical bifurcation. The overall study reveals complex dynamics of the FG pipe with respect to some system parameters like temperature of fluid, material properties of FGM and fluid flow velocity. © 2019, Springer Nature B.V.

Nonlinear Dynamics

Nonlinear dynamics of functionally graded pipes conveying hot fluid

β-diketiminate coordinated magnesium(I) compounds, [{(ArNacnac)Mg}2] (ArNacnac = [(ArNCMe)2CH]- (Ar = 2,6-diisopropylphenyl (Dip) or mesityl (Mes)), have been utilized as reducing agents in reactions with the redox active 1,4-diazabutadiene, (ButNCH)2 (ButDAB) and 2,2′-bipyrine (bipy). These reactions led to one-electron reductions of the unsaturated substrate and formation of the highly colored radical complexes, [(ArNacnac) Mg(ButDAB.)] and [(MesNacnac)Mg(bipy.)(bipy)]. The X-ray crystal structures of the compounds reveal each to possess one singly reduced ButDAB or bipy ligand. © 2020 Yuvaraj and Jones.

Department of Chemistry

Main Group Metal Chemistry

Reduction of a 1, 4-diazabutadiene and 2, 2’-bipyridine using magnesium (I) compounds

An extremely bulky, symmetrical three-coordinate magnesium(i) complex, [{(TCHPNacnac)Mg}2] (TCHPNacnac = [{(TCHP)NCMe}2CH]-, TCHP = 2,4,6-tricyclohexylphenyl) has been prepared and shown to have an extremely long Mg-Mg bond (3.021(1) Å) for such a complex. It was shown not to react with either DMAP (4-dimethylaminopyridine) or CO. Three unsymmetrical 1 : 1 DMAP adducts of less bulky Mg-Mg bonded species have been prepared, viz. [(ArNacnac)Mg-Mg(DMAP)(ArNacnac)] (ArNacnac = [(ArNCMe)2CH]- Ar = 2,6-xylyl (Xyl), mesityl (Mes) or 2,6-diethylphenyl (Dep)) and their reactivity toward CO explored. Like the previously reported bulkier complex, [(DipNacnac)Mg-Mg(DMAP)(DipNacnac)] (Dip = 2,6-diisopropylphenyl), [(DepNacnac)Mg-Mg(DMAP)(DepNacnac)] reductively trimerises CO to give a rare example of a deltate complex, [{(DepNacnac)Mg(μ-C3O3)Mg(DMAP)(DepNacnac)}2]. In contrast, the two smaller adduct complexes react with only two CO molecules, ultimately giving unusual ethenediolate complexes [{(ArNacnac)Mg{μ-OC(H)C(DMAP-H)O}Mg(ArNacnac)}2] (Ar = Xyl or Mes). DFT calculations show the latter reactions to proceed via reductive dimerizations of CO and subsequent intramolecular C-H activation of Mg-ligated DMAP by "zig-zag" [C2O2]2- fragments of reaction intermediates. Calculations also suggest that magnesium deltate complexes are kinetic products in these reactions, while the magnesium ethenediolates are thermodynamic products. This study shows that subtle changes to the bulk of the reacting 1 : 1 DMAP-magnesium(i) adduct complexes can lead to fine steric control over the products arising from their CO reductive oligomerisations. Furthermore, it is found that the more activated nature of the adduct complexes, relative to their symmetrical, three-coordinate counterparts, [{(ArNacnac)Mg}2], likely derives more from the polarisation of the Mg-Mg bonds of the former, than the elongated nature of those bonds. This journal is © The Royal Society of Chemistry.

Chemical Science

Sterically controlled reductive oligomerisations of CO by activated magnesium (I) compounds: deltate vs. ethenediolate formation

An r-partite tournament is a directed graph obtained by assigning a unique orientation to each edge of a complete undirected r-partite simple graph. Given a bipartite tournament T on n vertices, we explore the parameterized complexity of the problem of determining if T has a cycle packing (a set of pairwise arc-disjoint cycles) of size k. Although the maximization version of this problem can be seen as the linear programming dual of the well-studied problem of finding a minimum feedback arc set (a set of arcs whose deletion results in an acyclic graph) in bipartite tournaments, surprisingly no algorithmic results seem to exist. We show that this problem can be solved in 2O(k log k)nO(1) time and admits a kernel with O(k2) vertices. © Springer Nature Switzerland AG 2020.