University of Calcutta

About: University of Calcutta is a education organization based out in Kolkata, India. It is known for research contribution in the topics: Population & Catalysis. The organization has 8900 authors who have published 19712 publications receiving 259067 citations. The organization is also known as: Calcutta University & CU.

An improved auto-tuning scheme for PI controllers.

Abstract: Ziegler-Nichols tuned PI and PID controllers are usually found to provide poor performances for high-order and nonlinear systems. In this study, an improved auto-tuning scheme is presented for Ziegler-Nichols tuned PI controllers (ZNPICs). With a view to improving the transient response, the proportional and integral gains of the proposed controller are continuously modified based on the current process trend. The proposed controller is tested for a number of high-order linear and nonlinear dead-time processes under both set-point change and load disturbance. It exhibits significantly improved performance compared to ZNPIC, and Refined Ziegler-Nichols tuned PI controller (RZNPIC). Robustness of the proposed scheme is established by varying the controller parameters as well as the dead-time of the process under control.

A new PT-symmetric complex Hamiltonian with a real spectrum

Abstract: We construct an isospectrum system in terms of a real and a complex potential to show that the underlying PT -symmetric complex Hamiltonian possesses a real spectrum which is shared by its real partner.

Syntheses, Structures, and Magnetic Properties of Diphenoxo-Bridged MIILnIII Complexes Derived from N,N‘-Ethylenebis(3-ethoxysalicylaldiimine) (M = Cu or Ni; Ln = Ce−Yb): Observation of Surprisingly Strong Exchange Interactions

Abstract: A series of heterodinuclear CuIILnIII and NiIILnIII complexes, [MIIL1LnIII(NO3)3] (M = Cu or Ni; Ln = Ce−Yb), with the hexadentate Schiff base compartmental ligand N,N‘-ethylenebis(3-ethoxysalicylaldiimine) (H2L1) have been synthesized and characterized. The X-ray crystal structure determinations of 13 of these compounds reveal that they are all isostructural. All of these complexes crystallize with the same orthorhombic P212121 space group with closely similar unit cell parameters. Typically, the structure consists of a diphenoxo-bridged 3d−4f dinuclear core, self-assembled to two dimensions due to the intermolecular nitrate···copper(II) or nitrate···nickel(II) semicoordination and weak C−H···O hydrogen bonds. Despite that, the metal centers of the neighboring units are well separated (the ranges of the shortest intermolecular contacts (A) are (M···M) 7.46−7.60, (Ln···Ln) 8.56−8.69, and (M···Ln) 6.12−6.20). Variable-temperature (5−300 K) magnetic susceptibility measurements of all the complexes have been...