National Institute of Technology, Meghalaya

About: National Institute of Technology, Meghalaya is a education organization based out in Shillong, India. It is known for research contribution in the topics: Control theory & Electric power system. The organization has 503 authors who have published 1062 publications receiving 6818 citations. The organization is also known as: NIT Meghalaya & NITM.

Examining the Aerodynamic Drag and Lift Characteristics of a Newly Developed Elliptical-Bladed Savonius Rotor

Abstract: The elliptical-bladed Savonius wind turbine rotor has become a subject of interest because of its better energy capturing capability. Hitherto, the basic parameters of this rotor such as overlap ratio, aspect ratio, and number of blades have been studied and optimized numerically. Most of these studies estimated the torque and power coefficients (CT and CP) at given flow conditions. However, the two important aerodynamic forces, viz., the lift and the drag, acting on the elliptical-bladed rotor have not been studied. This calls for a deeper investigation into the effect of these forces on the rotor performance to arrive at a suitable design configuration. In view of this, at the outset, two-dimensional (2D) unsteady simulations are conducted to find the instantaneous lift and drag forces acting on an elliptical-bladed rotor at a Reynolds number (Re) = 0.892 × 105. The shear stress transport (SST) k–ω turbulence model is used for solving the unsteady Reynolds averaged Navier–Stokes equations. The three-dimensional (3D) unsteady simulations are then performed which are then followed by the wind tunnel experiments. The drag and lift coefficients (CD and CL) are analyzed for 0–360 deg rotation of rotor with an increment of 1 deg. The total pressure, velocity magnitude, and turbulence intensity contours are obtained at various angles of rotor rotation. For the elliptical-bladed rotor, the average CD, CL, and CP, from 3D simulation, are found to be 1.31, 0.48, and 0.26, respectively. The average CP for the 2D elliptical profile is found to be 0.34, whereas the wind tunnel experiments demonstrate CP to be 0.19.

Match-Line Division and Control to Reduce Power Dissipation in Content Addressable Memory

Abstract: Hardware search engines are widely used in network routers for high-speed look up and parallel data processing. Content addressable memory (CAM) is such an engine that performs high-speed search at the expense of large energy dissipation. Match-line (ML) power dissipation is one of the critical concerns in designing low-power CAM architectures. NOR-MLs make this issue more severe due to the higher number of short-circuit discharge paths during search. In this paper, an ML control scheme is presented that enables dynamic evaluation of a match-line by effectively activating or deactivating ML sections to improve the energy efficiency. $128{\boldsymbol \times }32$ -bit memory arrays have been designed using 45-nm CMOS technology and verified at different process-voltage-temperature and frequency variations to test the improvements of performance. A search frequency of 100 MHz under 1-V supply, at 27 °C applied on the proposed CAM results 48.25%, 52.55%, and 54.80% reduction in energy per search compared to a conventional CAM, an early predict and terminate ML precharge CAM (EPTP-CAM) and an ML selective charging scheme CAM, respectively. ML partition also minimizes precharge activities between subsequent searches to reduce total precharge power in the proposed scheme. An approximate reduction of 2.5 times from conventional and EPTP schemes is observed in the precharge dissipation. Besides low search power, proposed design improves the energy-delay by 42% to 88% from compared designs.

Explicit impacts of harvesting in delayed predator-prey models

Abstract: Modeling population dynamics using delay differential equations and exploring the impacts of harvesting in predator-prey systems are among few of the thrust areas of research in theoretical and applied ecology. Many results are established to understand distinct dynamics under population harvesting. However, comparatively less attention is paid to explain the explicit harvesting effects when populations fluctuate due to time delay. In this contribution, two well known Lotka–Volterra (LV) type and Rosenzweig–MacArthur (RM) predator-prey models incorporating time delay into the logistic growth term are considered. The analysis and the obtained results are summarized as follows. (a) Firstly, the dynamics of both the models, by considering the time delay as the bifurcation parameter, is analyzed. Some of the parameter conditions for the delay induced stability switching are improved and corrected in comparison to the earlier works. The delay induced stability results are derived and found to be similar for both the models. (b) We investigate whether harvesting of either prey or predator can locally stabilize (respectively, destabilize) the system when the unharvested system dynamics is at non-equilibrium (respectively, stable steady state) mode due to time delay. It is observed that harvesting can induce stability and instability switching depending upon the dynamics mode of the unharvested system. (c) In the same framework, we examine if a stable steady state can be obtained when predator is harvested towards Maximum Sustainable Yield (MSY) level. Unlike the case of non-delayed LV type and RM predator-prey models, it is found that harvesting the predator towards MSY in the delayed models does not guarantee a stable stock. The new results compared to the existing literature might contribute in enriching fishery management policy and theoretical ecology as a whole.

Sorption Isotherms, Kinetics, and Thermodynamics of Contaminants in Indian Soils

Abstract: The sorption isotherms, kinetics, and thermodynamics of contaminants, e.g., strontium, lead, and uranium, for four different Indian soils (named S1, S2, S3, and S4) were investigated. Batch...

Effects of PET fiber arrangement and dimensions on mechanical properties of concrete

Abstract: Concrete has low tensile strength and crack resistance. Its weaknesses could be enhanced with the addition of fiber. Polyethylene terephthalate (PET) fibers are generally used in concrete as discrete reinforcement in substitution of steel fiber. Fibers obtained by hand cutting of PET bottles are in the form of straight slit sheets, which impart weaker bonding in concrete matrix. The bonding of the fibers however may be improved by using other geometries such as flattened-end sheet pattern. So far, there are no guidelines for defining the geometry and dimensions of PET fibers. Therefore, this paper focuses on the use of fibers with different geometries and dimensions and investigates their effects on the mechanical properties of concrete. Test results show that geometry of fibers has a small effect on the workability of concrete. The use of smaller dimensions of fiber improves the workability. Enhancement in the strength and energy dissipation capacity of fiber concretes was observed from the use of flatte...