Indian Institute of Technology Indore

About: Indian Institute of Technology Indore is a education organization based out in Indore, Madhya Pradesh, India. It is known for research contribution in the topics: Fading & Support vector machine. The organization has 1606 authors who have published 4803 publications receiving 66500 citations.

On Performance of Hexagonal, Cross, and Rectangular QAM for Multi-Relay Systems

Abstract: Error performance is considered as one of the most important performance measures, and deriving the closed-form expressions for efficient modulation techniques over generalized fading channels is important for future cellular systems. In this paper, the performance of a dual-hop amplify-and-forward multi-relay system with best relay selection is analyzed over independent and non-identically distributed (i.n.i.d.) Nakagami-m fading links with both integer and non-integer fading parameters. The impact of practical constraints of imperfect channel state information (CSI) and non-linear power amplifier (NLPA) at each of the relays are considered. Closed-form expressions for the outage probability are derived for both integer and non-integer fading parameters, and asymptotic analysis on the outage probability is performed to obtain the diversity order of the considered multi-relay system. Based on the cumulative distribution function approach, average symbol error rate (ASER) expressions for general order hexagonal QAM, general order rectangular QAM, and 32-cross QAM schemes are also derived. The comparative analysis of ASER for various QAM schemes with different constellations is also illustrated. Furthermore, the impact of the number of relays, fading parameter, channel estimation error, and non-linear distortion on the system performance is also highlighted. Finally, the derived analytical results are validated through Monte-Carlo simulations.

Mesoporous layered hexagonal platelets of Co3O4 nanoparticles with (111) facets for battery applications: high performance and ultra-high rate capability

Abstract: The thermally stable and crystalline 2D layered mesoporous hexagonal platelets of cobalt oxide (Co3O4) with (111) facets were prepared by using the template-free wet chemical synthesis approach. The high surface energy (111) facets known for a highly electroactive surface are expected to enhance the electrochemical properties, especially the rate capability. The highly crystalline Co3O4 with an average particle size of 25 nm formed a 2D mesoporous layered structure, with an average thickness of ∼40 nm, a pore size of 8–10 nm, and a specific surface area of 45.68 m2 g−1 promoting large surface confined electrochemical reaction. The 2D layered mesoporous Co3O4 exhibits a maximum specific capacity of 305 mA h g−1 at a scan rate of 5 mV s−1 and 137.6 mA h g−1 at a current density of 434.8 mA g−1. The maximum energy and power densities of 32.03 W h kg−1 and 9.36 kW kg−1, respectively, are achieved from the 2D hexagonal platelets of mesoporous Co3O4 nanoparticles with (111) facets. An excellent ultra-high rate capability of ∼62% capacity retention was observed after increasing the discharge current density from ∼434.8 mA g−1 to 43 480 mA g−1. Furthermore, a cycling stability of 81.25% was achieved even after 2020 charge–discharge cycles at a current density of 12 170 mA g−1. This high performance and ultra-high rate capability could be attributed to the (111) facets ‘crystal plane’ effect of Co3O4. Our results presented here confirm that the 2D mesoporous layered hexagonal platelets of Co3O4 exhibit “battery-mimic” behaviour in an aqueous electrolyte of KOH.

Solid-state synthesis of stable and color tunable cesium lead halide perovskite nanocrystals and the mechanism of high-performance photodetection in a monolayer MoS2/CsPbBr3 vertical heterojunction

Abstract: Herein, we report on a facile room-temperature bulk scale solid-state synthesis of highly luminescent color-tunable CsPbX3 nanocrystals (NCs) with superior optoelectronic performance and exceptional ambient stability. The composition tuned all-inorganic perovskite NCs exhibit high photoluminescence (PL) quantum yield with adjustable emission color in the range 416–691 nm and high color purity (linewidth ∼14 nm). The as-grown NCs are highly stable up to seven months under ambient conditions, and the post-growth annealing results in reduced non-radiative recombination centers and improved PL quantum yield (∼95%) in the perovskite NCs. The low-temperature PL study reveals high exciton binding energy in the NCs, and the highly luminescent perovskite NCs were utilized for the demonstration of color-tunable light-emitting diodes with high luminous efficiency (∼42 lm W−1 for CsPbBr3). We further integrate the CsPbBr3 NCs on direct CVD grown large-area monolayer MoS2 on Si/SiO2 substrates and fabricate a vertical heterojunction photodetector (PD). For the first time, direct CVD grown large area 1L-MoS2 on Si/SiO2 has been utilized here to demonstrate a 1L-MoS2/CsPbBr3 PD of type-II heterojunction with high responsivity (24.3 A W−1 at 405 nm) and extremely fast photo-response with photocurrent growth and decay times of 5.5 μs and 24.0 μs, respectively. The superior performance of the heterojunction PD is attributed to the fast transfer of photogenerated electrons from CsPbBr3 NCs to monolayer MoS2 and n-doping of the MoS2. Our interpretation is fully supported by density functional theory based electronic structure calculations and Kelvin probe force microscopy measurements, which show direct evidence of the charge transfer at the MoS2/CsPbBr3 heterojunction due to a type-II band alignment. Our results pave the way for the large-scale synthesis of highly stable and color-tunable CsPbX3 NCs and their application in bright LEDs and a high-performance photodetector with a fast response.

Multiplicity dependence of two-particle azimuthal correlations in pp collisions at the LHC

Abstract: We present the measurements of particle pair yields per trigger particle obtained from di-hadron azimuthal correlations in pp collisions at root s = 0.9, 2.76, and 7TeV recorded with the ALICE detector. The yields are studied as a function of the charged particle multiplicity. Taken together with the single particle yields the pair yields provide information about parton fragmentation at low transverse momenta, as well as on the contribution of multiple parton interactions to particle production. Data are compared to calculations using the PYTHIA6, PYTHIA8, and PHOJET event generators.

Tuning the Fluorescence and the Intramolecular Charge Transfer of Phenothiazine Dipolar and Quadrupolar Derivatives by Oxygen Functionalization.

Abstract: A series of new naphthalimide and phenothiazine-based push-pull systems (NPI-PTZ1-5), in which we structurally modulate the oxidation state of the sulfur atom in the thiazine ring, i.e., S(II), S(IV), and S(VI), was designed and synthesized by the Pd-catalyzed Sonogashira cross-coupling reaction. The effect of the sulfur oxidation state on the spectral, photophysical, and electrochemical properties was investigated. The steady-state absorption and emission results show that oxygen functionalization greatly improves the optical (absorption coefficient and fluorescence efficiency) and nonlinear optical (hyperpolarizability) features. The cyclic voltammetry experiments and the quantum mechanical calculations suggest that phenothiazine is a stronger electron donor unit relative to phenothiazine-5-oxide and phenothiazine-5,5-dioxide, while the naphthalimide is a strong electron acceptor in all cases. The advanced ultrafast spectroscopic measurements, transient absorption, and broadband fluorescence up conversion give insight into the mechanism of photoinduced intramolecular charge transfer. A planar intramolecular charge transfer (PICT) and highly fluorescent excited state are populated for the oxygen-functionalized molecules NPI-PTZ2,3 and NPI-PTZ5; on the other hand, a twisted intramolecular charge transfer (TICT) state is produced upon photoexcitation of the oxygen-free derivatives NPI-PTZ1 and NPI-PTZ4, with the fluorescence being thus significantly quenched. These results prove oxygen functionalization as a new effective synthetic strategy to tailor the photophysics of phenothiazine-based organic materials for different optoelectronic applications. While oxygen-functionalized compounds are highly fluorescent and promising active materials for current-to-light conversion in organic light-emitting diode devices, oxygen-free systems show very efficient photoinduced ICT and may be employed for light-to-current conversion in organic photovoltaics.