Faculty Publications

Now showing 1 - 4 of 4

Linear Voltage Amplifier for High Voltage Applications
(Institute of Electrical and Electronics Engineers Inc., 2022) Nithin Reddy, G.N.; Iyer, S.R.; Agrawal, S.; Reddy B, S.
High voltage measurements require precision high voltage instruments for dielectric measurements and for other high voltage applications. The present work requires linear, high voltage, and high-frequency bandwidth supply, which must be precisely monitored and controlled. High voltage engineers crave automated control of supply through safer control techniques. The paper presents a high voltage supply used as a linear high voltage amplifier that amplifies the low voltage input of Â±5 V with a gain of 40 per unit this is obtained using TINA software. The novel linear high-voltage amplifier circuit proposed will be useful for insulation measurements, electrostatic applications, dielectric measurements, and other industrial applications. An attempt is made to develop the hardware for the proposed amplifier. Â© 2022 IEEE.
Optimizing the position of insulating materials in flat roofs exposed to sunshine to gain minimum heat into buildings under periodic heat transfer conditions
(Springer Verlag service@springer.de, 2016) Saboor, S.; Ashok Babu, A.B.P.S.
Building roofs are responsible for the huge heat gain in buildings. In the present work, an analysis of the influence of insulation location inside a flat roof exposed directly to the sun’s radiation was performed to reduce heat gain in buildings. The unsteady thermal response parameters of the building roof such as admittance, transmittance, decrement factor, and time lags have been investigated by solving a one-dimensional diffusion equation under convective periodic boundary conditions. Theoretical results of four types of walls were compared with the experimental results available in literature. The results reveal that the roof with insulation placed at the outer side and at the center plane of the roof is the most energy efficient from the lower decrement factor point of view and the roof with insulation placed at the center plane and the inner side of the roof is the best from the highest time lag point of view among the seven studied configurations. The composite roof with expanded polystyrene insulation located at the outer side and at the center plane of the roof is found to be the best roof from the lowest decrement factor (0.130) point of view, and the composite roof with resin-bonded mineral wool insulation located at the center plane and at the inner side of the roof is found to be energy efficient from the highest time lag point (9.33 h) of view among the seven configurations with five different insulation materials studied. The optimum fabric energy storage thicknesses of reinforced cement concrete, expanded polystyrene, foam glass, rock wool, rice husk, resin-bonded mineral wool, and cement plaster were computed. From the results, it is concluded that rock wool has the least optimum fabric energy storage thickness (0.114 m) among the seven studied building roof materials. © 2015, Springer-Verlag Berlin Heidelberg.
Charge-transfer interface of insulating metal-organic frameworks with metallic conduction
(Nature Research, 2022) Sindhu, P.; Ananthram, K.S.; Jain, A.; Tarafder, K.; Ballav, N.
Downsizing materials into hetero-structured thin film configurations is an important avenue to capture various interfacial phenomena. Metallic conduction at the interfaces of insulating transition metal oxides and organic molecules are notable examples, though, it remained elusive in the domain of coordination polymers including metal-organic frameworks (MOFs). MOFs are comprised of metal centers connected to organic linkers with an extended coordination geometry and potential void space. Poor orbitals overlap often makes these crystalline solids electrical insulators. Herein, we have fabricated hetero-structured thin film of a Mott and a band insulating MOFs via layer-by-layer method. Electrical transport measurements across the thin film evidenced an interfacial metallic conduction. The origin of such an unusual observation was understood by the first-principles density functional theory calculations; specifically, Bader charge analysis revealed significant accumulation and percolation of charge across the interface. We anticipate similar interfacial effects in other rationally designed hetero-structured thin films of MOFs. © 2022, The Author(s).
Insulator-to-metal-like transition in thin films of a biological metal-organic framework
(Nature Research, 2023) Sindhu, P.; Ananthram, K.S.; Jain, A.; Tarafder, K.; Ballav, N.
Temperature-induced insulator-to-metal transitions (IMTs) where the electrical resistivity can be altered by over tens of orders of magnitude are most often accompanied by structural phase transition in the system. Here, we demonstrate an insulator-to-metal-like transition (IMLT) at 333 K in thin films of a biological metal-organic framework (bio-MOF) which was generated upon an extended coordination of the cystine (dimer of amino acid cysteine) ligand with cupric ion (spin-1/2 system) – without appreciable change in the structure. Bio-MOFs are crystalline porous solids and a subclass of conventional MOFs where physiological functionalities of bio-molecular ligands along with the structural diversity can primarily be utilized for various biomedical applications. MOFs are usually electrical insulators (so as our expectation with bio-MOFs) and can be bestowed with reasonable electrical conductivity by the design. This discovery of electronically driven IMLT opens new opportunities for bio-MOFs, to emerge as strongly correlated reticular materials with thin film device functionalities. © 2023, The Author(s).

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