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.

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IIT Palakkad

We consider a biphasic continuum model for avascular tumour growth in two spatial dimensions, in which a cell phase and a fluid phase follow conservation of mass and momentum. A limiting nutrient that follows a diffusion process controls the birth and death rate of the tumour cells. The cell volume fraction, cell velocity–fluid pressure system, and nutrient concentration are the model variables. A coupled system of a hyperbolic conservation law, a viscous fluid model, and a parabolic diffusion equation governs the dynamics of the model variables. The tumour boundary moves with the normal velocity of the outermost layer of cells, and this time-dependence is a challenge in designing and implementing a stable and fast numerical scheme. We recast the model into a form where the hyperbolic equation is defined on a fixed extended domain and retrieve the tumour boundary as the interface at which the cell volume fraction decreases below a threshold value. This procedure eliminates the need to track the tumour boundary explicitly and the computationally expensive re-meshing of the time-dependent domains. A numerical scheme based on finite volume methods for the hyperbolic conservation law, Lagrange P2- P1 Taylor-Hood finite element method for the viscous system, and mass-lumped finite element method for the parabolic equations is implemented in two spatial dimensions, and several cases are studied. We demonstrate the versatility of the numerical scheme in catering for irregular and asymmetric initial tumour geometries. When the nutrient diffusion equation is defined only in the tumour region, the model depicts growth in free suspension. On the contrary, when the nutrient diffusion equation is defined in a larger fixed domain, the model depicts tumour growth in a polymeric gel. We present numerical simulations for both cases and the results are consistent with theoretical and heuristic expectations such as early linear growth rate and preservation of radial symmetry when the boundary conditions are symmetric. The work presented here could be extended to include the effect of drug treatment of growing tumours. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

World University root node

Department of Mathematics

Fulltext

Journal of Scientific Computing

Numerical Solution of a Two Dimensional Tumour Growth Model with Moving Boundary

We revisit the issue of Lagrangian irreversibility in the context of recent results [H. Xu, Proc. Natl. Acad. Sci. USA 111, 7558 (2014)PNASA60027-842410.1073/pnas.1321682111] on flight-crash events in turbulent flows and show how extreme events in the Eulerian dissipation statistics are related to the statistics of power fluctuations for tracer trajectories. Surprisingly, we find that particle trajectories in intense dissipation zones are dominated by energy gains sharper than energy losses, contrary to flight crashes, through a pressure-gradient driven take-off phenomenon. Our conclusions are rationalized by analyzing data from simulations of three-dimensional intermittent turbulence, as well as from nonintermittent decimated flows. Lagrangian irreversibility is found to persist even in the latter case, wherein fluctuations of the dissipation rate are shown to be relatively mild and to follow probability distribution functions with exponential tails. © 2020 American Physical Society. ©2020 American Physical Society.

Department of Physics

Physical Review Fluids

Lagrangian irreversibility and Eulerian dissipation in fully developed turbulence

The conceptual design of a new sitting-type lower-limb rehabilitation robot along with simplified motion control for its passive range of motion therapies is put forth here. The suggested system’s design is demonstrated and verified using computer-based numerical simulations. For this, the desired motion trajectory is generated with the help of a clinically obtained gait data-set. The robustness of the proposed simplified motion control scheme is verified with the variation of the physical parameters of the patients’ limb. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2020.

Department of Mechanical Engineering

Mechanisms and Machine Science

Conceptual Design and Control of a Sitting-Type Lower-Limb Rehabilitation System Established on a Spatial 3-PRRR Parallel Manipulator

This paper considers a resolved kinematic motion control approach for controlling a spatial serial manipulator arm that is mounted on a vehicle base. The end-effector's motion of the manipulator is controlled by a novel kinematic control scheme, and the performance is compared with the well-known operational-space control scheme. The proposed control scheme aims to track the given operational-space (end-effector) motion trajectory with the help of resolved configuration-space motion without using the Jacobian matrix inverse or pseudo inverse. The experimental testing results show that the suggested control scheme is as close to the conventional operational-space kinematic control scheme. © 2020, DESIDOC

Defence Science Journal

Simplified motion control of a vehicle-manipulator for the coordinated mobile manipulation

Intervention-class autonomous underwater vehicles (AUVs) have to execute complex tasks such as underwater inspection and manipulating objects which demand high manoeuvrability along with good stability. Due to these contrasting capabilities, often the vehicle control activity demands high actuator outputs with almost zero time response. This condition leads to actuator saturation and limits the vehicle response to the control inputs. Another factor to be considered is the thrusters hydrodynamic constraints during propulsion which results in a highly nonlinear and coupled equations of motions. This forms the basic motivation to design a suitable nonlinear control methodology by considering the empirical data based thrust modelling, drag effects of the propulsion, and interaction effects of the external appendages and the hull of the vehicle. The capability of the proposed control strategy is evaluated by implementing a trajectory tracking problem. The simulation results prove the capability of the proposed control strategy to execute complex tasks in the presence of actuator saturation and hydrodynamic constraints. © 2020 IEEE.

2020 Global Oceans 2020: Singapore - U.S. Gulf Coast

Control of a vectorial propulsion underwater vehicle considering thruster hydrodynamics constraints and actuator saturation

Complex and interactive robot manipulation skills, such as playing a game of table tennis against a human opponent, are a novel problem with multifaceted challenges. Accurate dynamic trajectory generation in order to respond to the tennis ball from the opponent and a novel control scheme for robust and high-performance tracking of the ball in such dynamic situations is a prerequisite to winning the game. In this paper, the dynamic movement primitives (DMPs) are employed for the stable generation of dynamic trajectories in the presence of environmental uncertainties such as ball position and velocity, opponent position and velocity and so on. In DMP, kernels parameters need to be found from expert demonstrations using a learning technique. To mitigate environmental uncertainties by accurate reconstruction of novel dynamic trajectories by combining multiple DMPs, we propose a piecewise linear canonical system (PLCS)-based modified DMP in contrast to the standard exponential canonical system (ECS)-based DMP. To enhance effectiveness and performance, a novel learning technique based on Lyapunov stability is embedded with the above-developed formulation. We show that the proposed learning technique is faster, has the best steady state error performance, and requires almost half the kernels than the state of the art. Next, to intercept the dynamic moving ball in real-time using the DMP, a novel control scheme is needed and designed using fuzzy fractional order sliding mode control. The control scheme results in chatter free tracking of the desired trajectories because the control law is free from sgn( cdot ) function. The tracking control performance is guaranteed theoretically via the Lyapunov approach and also verified through simulations and experiments. Finally, we have developed a complete system (including a vision system for tracking the ball) using a real 4 degrees-of-freedom (DOFs) Barrett Wam robotic arm and show that the proposed overall framework is able to respond to a hanging ball with high accuracy. © 1993-2012 IEEE.

IEEE Transactions on Control Systems Technology

Dynamic Trajectory Generation and a Robust Controller to Intercept a Moving Ball in a Game Setting

The article describes the structure of the lower limb rehabilitation system based on serial RRRR mechanism as a passive orthosis and an active parallel 3-PRRR mechanism. A mathematical model of the kinematics of the RRRR mechanism is presented. A description of a numerical method for determining the workspace of the RRRR mechanism based on the approximation of solutions of nonlinear inequalities systems to provide the required rotation angles in joints for rehabilitation is considered. A calculation algorithm, a software, and a visualization system for export the three-dimensional workspaces in STL format are synthesized. The results of mathematical modeling and analysis of the results are presented. © 2020, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.

A numerical method for determining the workspace of a passive orthosis based on the rrrr mechanism in the lower limb rehabilitation system

We explore correlations between dynamics of different microtubules in a bundle, via numerical simulations, using a one-dimensional stochastic model of a microtubule. The guanosine triphosphate (GTP)-bound tubulins undergo diffusion-limited binding to the tip. Random hydrolysis events take place along the microtubule and converts the bound GTP in tubulin to guanosine diphosphate (GDP). The microtubule starts depolymerising when the monomer at the tip becomes GDP-bound; in this case, detachment of GDP-tubulin ensues and continues until either GTP-bound tubulin is exposed or complete depolymerisation is achieved. In the latter case, the microtubule is defined to have undergone a “catastrophe”. Our results show that, in general, the dynamics of growth and catastrophe in different microtubules are coupled to each other; the closer the microtubules are, the stronger the coupling. In particular, all microtubules grow slower, on average, when brought closer together. The reduction in growth velocity also leads to more frequent catastrophes. More dramatically, catastrophe events in the different microtubules forming a bundle are found to be correlated; a catastrophe event in one microtubule is more likely to be followed by a similar event in the same microtubule. This propensity of bunching disappears when the microtubules move farther apart. © 2020, European Biophysical Societies' Association.

European Biophysics Journal

Spatio-temporal correlations between catastrophe events in a microtubule bundle: a computational study

Normal thermal fluctuations of the cell membrane have been studied extensively using high resolution microscopy and focused light, particularly at the peripheral regions of a cell. We use a single probe particle attached non-specifically to the cell-membrane to determine that the power spectral density is proportional to (frequency)-5/3 in the range of 5 Hz to 1 kHz. We also use a new technique to simultaneously ascertain the slope fluctuations of the membrane by relying upon the determination of pitch motion of the birefringent probe particle trapped in linearly polarized optical tweezers. In the process, we also develop the technique to identify pitch rotation to a high resolution using optical tweezers. We find that the power spectrum of slope fluctuations is proportional to (frequency)-1, which we also explain theoretically. We find that we can extract parameters like bending rigidity directly from the coefficient of the power spectrum particularly at high frequencies, instead of being convoluted with other parameters, thereby improving the accuracy of estimation. We anticipate this technique for determination of the pitch angle in spherical particles to high resolution as a starting point for many interesting studies using the optical tweezers. This journal is © The Royal Society of Chemistry.

Soft Matter

Detection of sub-degree angular fluctuations of the local cell membrane slope using optical tweezers

Landfill cover barriers are susceptible to flexural distress due to the differential settlements caused by biodegradation and heterogeneous composition of the underlying waste. The effect of discrete fibre inclusions on the flexural distress of landfill cover barriers was studied using centrifuge model tests. Three types of fibres were used: polyester (PET), polypropylene-tape (PP-T) and polypropylene-fibrillated (PP-F). For unreinforced barriers (UB), the crack initiation and water breakthrough were observed at low distortion levels compared to identical fibre-reinforced barriers (FB). The strain at crack initiation and strain at water breakthrough for FB was 2.36 times and 2.76 times higher than identical UB, respectively. Also, suppression of the cracks and improved water tightness was observed due to the overburden pressure in both UB and FB. PET fibre-reinforced barriers were found to be superior in maintaining the water tightness of the barrier compared to PP-T and PP-F fibres used in the present study. Propagation of cracks penetrating through the thickness of the soil barrier was significantly restrained by the fibres irrespective of the fibre type. Scanning electron micrographs of exhumed fibres indicated that the fibres in the present study were distorted and participated in taking tension due to differential settlements. © 2020 Thomas Telford Ltd