Spiral-wave dynamics in a mathematical model of human ventricular tissue with myocytes and Purkinje fibers

We present systematic numerical studies of the possible effects of the coupling of human endocardial and Purkinje cells at cellular and two-dimensional tissue levels. We find that the autorhythmic-activity frequency of the Purkinje cell in a composite decreases with an increase in the coupling strength; this can even eliminate the autorhythmicity. We observe a delay between the beginning of the action potentials of endocardial and Purkinje cells in a composite; such a delay increases as we decrease the diffusive coupling, and eventually a failure of transmission occurs. An increase in the diffusive coupling decreases the slope of the action-potential-duration-restitution curve of an endocardial cell in a composite. By using a minimal model for the Purkinje network, in which we have a two-dimensional, bilayer tissue, with a layer of Purkinje cells on top of a layer of endocardial cells, we can stabilize spiral-wave turbulence; however, for a sparse distribution of Purkinje-ventricular junctions, at which these two layers are coupled, we can also obtain additional focal activity and many complex transient regimes. We also present additional effects resulting from the coupling of Purkinje and endocardial layers and discuss the relation of our results to the studies performed in anatomically accurate models of the Purkinje network

Geometric Nonlinear Finite Element and Genetic Algorithm Based Vibration Energy Harvesting from Functionally Graded Nonprismatic Piezolaminated Beams

Energy harvesting technology has the ability to create autonomous, self-powered systems which do not rely on the conventional battery for their operation. The term energy harvesting is the process of converting the ambient energy surrounding a system into some useful electrical energy using certain materials. Among several energy conversion techniques, the conversion of ambient vibration energy to electrical energy using piezoelectric materials has great deal of importance which encompasses electromechanical coupling between mechanical and electrical domains. The energy harvesting systems are designed by incorporating the piezoelectric materials in the host structure located in vibration rich environment. The work presented in this dissertation focuses on upgrading the concept of energy harvesting in order to engender more power than conventional energy harvesting designs. The present work deals with first the finite element (FE) formulation for coupled thermo-electro-mechanical analysis of vibration energy harvesting from an axially functionally graded (FG) non-prismatic piezolaminated cantilever beam. A two noded beam element with two degrees of freedom (DOF) at each node has been used in the FE formulation. The FG material (i.e. non-homogeneity) in the axial direction has been considered which varies (continuously decreasing from root to tip of such cantilever beam) using a proposed power law formula. The various cross section profiles (such as linear, parabolic and cubic) have been modelled using the Euler-Bernoulli beam theory and Hamilton‘s principle is used to solve the governing equation of motion. The simultaneous variation of tapers (both width and height in length directions) is incorporated in the mathematical formulation. The FE formulation developed in the present work has been compared with the analytical solutions subjected to mechanical, electrical, thermal and thermo-electro-mechanical loading. Results obtained from the present work shows that the axially FG nonprismatic beam generates more output power than the conventional energy harvesting systems. Further, the work has been focussed towards the nonlinear vibration energy harvesting from an axially FG non-prismatic piezolaminated cantilever beam. Geometric nonlinear based FE formulation using Newmark method in conjunction with Newton-Raphson method has been formulated to solve the obtained governing equation. Moreover, a real code GA based constrained optimization technique has also been proposed to determine the best possible design variables for optimal power harvesting within the allowable limits of ultimate stress of the beam and voltage of the PZT sensor. It is observed that more output power can be obtained based on the present optimization formulation within the allowable limits of stress and voltage than that of selection of design variables by trial and error in FE modelling

Design of Door Handle

Doors are the most essential hardware used by human beings daily. Doors are used for sense of security to ourselves. To operate the door we need door handle and it’s the most important part in door. Door handles are used for opening and closing of a door with minimum effort. Various types of door handles such as lever handle, doorknob and pull handles are the different kind of handles we came across in our day to day life. There are various designs of door handles are available so that we are unaware of door handles selection criteria. Different shapes can be designed on the basis of user reaction to the available door handle. How we operate on the door handle is one key factor for selection of door handle. There are various other factors associate with door handle such as style, comfort, cost etc. It’s not just a device used for opening and closing of door but also for locking purpose. Door handles are divided on the basis of different types of door, finishes, and shapes

Estimation of exact equivalent parameters of synchronous machines for power system studies

Synchronous generators form the principal source of electrical energy in power system. Many large loads are driven by synchronous motors. For stability studies of large power systems, accurate representation of the synchronous machine is required. The synchronous machine equations have the inductances and resistances of the stator and rotor circuits as parameters. These are referred to as fundamental parameters or basic parameters. While the fundamental parameters completely specify the machine electrical characteristics, they cannot be directly determined from measured responses of the machine. Therefore, the traditional approach to assigning machine data has been to express them in terms of derived parameters that are related to observed behavior as viewed from the terminals under suitable test conditions. This project is aimed at modeling and analyzing different models of synchronous machine. Models with different number of damper windings are analyzed and fundamental parameters of the machine are obtained using manufacturer‟s data. Newton Raphson method is used to solve the rotor and stator equations for the equivalent circuits of models and simulated in MATLAB. An experimental data is used to simulate the models and results are studied. Frequency domain analysis is performed to obtain transient time constants and compared with those obtained from computer simulation

A comparative study of early afterdepolarization-mediated fibrillation in two mathematical models for human ventricular cells

Early afterdepolarizations (EADs), which are abnormal oscillations of the membrane potential at the plateau phase of an action potential, are implicated in the development of cardiac arrhythmias like Torsade de Pointes. We carry out extensive numerical simulations of the TP06 and ORd mathematical models for human ventricular cells with EADs. We investigate the different regimes in both these models, namely, the parameter regimes where they exhibit (1) a normal action potential (AP) with no EADs, (2) an AP with EADs, and (3) an AP with EADs that does not go back to the resting potential. We also study the dependence of EADs on the rate of at which we pace a cell, with the specific goal of elucidating EADs that are induced by slow or fast rate pacing. In our simulations in two-and three-dimensional domains, in the presence of EADs, we find the following wave types: (A) waves driven by the fast sodium current and the L-type calcium current (Na-Ca-mediated waves); (B) waves driven only by the L-type calcium current (Ca-mediated waves); (C) phase waves, which are pseudo-travelling waves. Furthermore, we compare the wave patterns of the various wave-types (Na-Ca-mediated, Ca-mediated, and phase waves) in both these models. We find that the two models produce qualitatively similar results in terms of exhibiting Na-Ca-mediated wave patterns that are more chaotic than those for the Ca-mediated and phase waves. However, there are quantitative differences in the wave patterns of each wave type. The Na-Ca-mediated waves in the ORd model show short-lived spirals but the TP06 model does not. The TP06 model supports more Ca-mediated spirals than those in the ORd model, and the TP06 model exhibits more phase-wave patterns than does the ORd model

VANET Based Four Way Road Intersection Traffic Light Control Model

Traffic lights are responsible in maintaining the smooth passage of traffic in urban scenario. To enhance the efficiency of traffic control system we are utilizing the concept of Vehicular Ad-hoc Network (VANET) along with our proposed VANET Based Four Way Road Intersection Traffic Light Control Model. The proposed model facilitates more number of vehicles to cross the intersection simultaneously; reduces the vehicles waiting time at intersection. The dynamic cycle traffic control provides an adaptive mechanism to adjust the timing behavior of traffic signal in accordance to traffic demand. Traffic density estimation and traffic density analysis are the two major phases of the proposed traffic signal control. The proposed system comprises of estimation of vehicle density in different lanes approaching the intersection. The density estimation is carried out using (V2I) Vehicle to Infrastructure and (V2V) Vehicle to Vehicle communication. Further the assessment and analysis of obtained data from the estimated density part is carried out by the traffic signal controller to adjust the traffic signal cycles in accordance with the traffic requirement such that unnecessary traffic waiting time can be minimized. The proposed model and proposed Green Light Allocation algorithm is evaluated against the existing static and dynamic cycle control system using Matlab. We found that our proposed system is giving better performance by allowing more traffic volume to cross through the intersection in each cycle. Also our proposed system is reducing the waiting time of vehicles at intersection by frequently switching the Green Light among the phases of same signal cycle