the visible to near-IR wavelengths of the electromagnetic spectrum. [9,10] Though organic-inorganic metal halides based perovskites can produce high photoluminescence (PL) yield, their instability makes it difficult for practical use. On the other side, all inorganic perovskite, e.g., cesium lead halides (CsPbX 3 ), based colloidal quantum dots attract much attention due to its very high PL yield (PLQY ≈ 90%), [11] narrow emission peak (enhanced color purity), low trap density, and reduced blinking [12] with high stability. Recent studies show ultralow threshold density (≈4.5 µJ cm −2 ) for amplified spontaneous emission (ASE) in CsPbBr 3 nanocrystals (NCs) film. [13,14] In past few years the successful employment of CsPbBr 3 quantum dots as light-emitting diodes, [9] single photon emitter, [15] advanced lasing material, [13] and photodetectors [16] make it necessary to have an in-depth study of different photophysical processes in this material. Some recent studies have been devoted to investigating excitonic recombination processes in this material at ultrafast timescale. [17] To date, most of these studies have been done at room temperature (RT). However, to understand the photoexcited carrier dynamics, temperature-dependent time-resolved PL (TRPL) study is an essential tool. Since PL lifetime can be significantly affected by the presence of surface traps, temperature-dependent TRPL gives us an insight of the trap-related kinetics in the NC. [18] Some recent studies [19,20] of the fine structure analysis of the excitonic and PL spectra of CsPbX 3 (X = Cl, Br, I) NCs show the presence of trion formation at low T. These trions are red-shifted by few meV from free excitons peak and decay radiatively with much faster rate than the excitons which results in faster PL decay at low T. [19,21] It has also been argued that the lowest triplet excitonic states are bright (emission red-shifted by few meV) in this material which is the cause of the higher photon emission rate. [22] Here, we have studied temperature-dependent TRPL decay of CsPbBr 3 NCs along with the steady-state absorption and PL to get insight into the influence of surface trap states on the emission kinetics in highly luminescent NCs. From timeresolved emission spectroscopy, we have found that the PL decaying faster at low temperature is in contrast to many other colloidal NCs such as PbS and CdS, [23,24] where PL lifetime gets extended by lowering the temperature. However, similar lengthening of PL lifetimes at elevated temperatures has also Temperature-dependent time-resolved photoluminescence (TRPL) spectroscopy of high optical gain CsPbBr 3 nanocrystals (NCs) films along with temperaturedependent steady-state absorption and photoluminescence (PL) spectra is studied. A red shift in the optical band edge and the corresponding PL peak is observed by lowering the temperature from room temperature, analogous to hybrid perovskite semiconductors. However, the faster PL decay of CsPbBr 3 NCs film at a low temperature as compared to room temperature is in con...

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Ultrasound waves are directly being used in many of the industrial applications including material removal for generating profiles on material surfaces. Trend has been shifted to use ultrasonic sound waves or ultrasonic vibrations as assisting media to enhance process performance. Electric discharge machining is one such industrial application for material removal, where ultrasonic vibrations have been introduced as assisting media for improving process performance. Ultrasonic vibrations were mainly employed in electric discharge machining process for improved debris evacuation from the sparking gap to increase process efficiency. It also resulted in stable and consistent sparking sequences by minimizing adverse arcing phenomenon in electric discharge machining. Since its introduction, technology of ultrasonic assistance in electric discharge machining has gone through considerable changes and penetrated to various variants of the electric discharge machining process mainly die sinking electric discharge machining, wire cut electric discharge machining and micro electric discharge machining.This article presents a research review for applications of ultrasonic vibrations for electric discharge machining process. The review has been carried out in terms of modes of applying ultrasonic vibrations, effect on performance parameters, process modelling and optimization and application for difficult-to-cut advanced materials. Based on the review of present status of the ultrasonic-assisted electric discharge machining, future research needs have been identified to strengthen the capacity and capabilities of the electric discharge machining process. KeywordsUltrasonic vibration, electric discharge machining, ultrasonic vibration-assisted electric discharge machining, die sinking electric discharge machining, wire cut electric discharge machining and micro electric discharge machining Date

Electrical discharge machining has emerged as the most popular non-conventional material removal process due to its novel variants, inherent process capability, and suitability for hybridization with other conventional and non-conventional material removal processes. However, high specific energy consumption, self-sacrificial electrode, hazardous emissions, toxic dielectric waste and sludge generation make this process one of the most unsustainable machining processes. Increased market competitiveness and requirement to comply with ISO 14000 standards demanded to implement sustainable manufacturing practices for short- and long-term business growth. In this article, the authors have reviewed the research work done in three of the sustainability indicators for the electrical discharge machining process, such as environmental impact, personnel health and operational safety. Modes of dielectric supply such as wet, dry and near dry have a paramount influence on the said sustainability indicators. Research works related to each indicator have been reviewed for the three modes of dielectric supply. This review provides a basis for understanding the current status of research activities for electrical discharge machining in the context of sustainability indicators. Future research needs have been discussed to make electrical discharge machining a more sustainable metal removal process.