A new atom transfer radical polymerization initiator based on phenolphthalein for the synthesis of bis‐allyloxy functionalized polystyrene macromonomers

A new atom transfer radical polymerization (ATRP) initiator, namely 2‐(1,1‐bis(4‐(allyloxy)phenyl)‐3‐oxoisoindolin‐2‐yl)ethyl 2‐bromo‐2‐methylpropanoate, was synthesized starting from phenolphthalein, a commercially available and an inexpensive chemical. Well‐ defined bis‐allyloxy functionalized polystyrene macromonomers (M_n,GPC 4800–11 700 g mol^?1) with controlled molecular weight and narrow molecular weight distribution (1.05–1.09) were synthesized using ATRP by varying the monomer to initiator feed ratio. The presence of allyloxy functionality on polystyrene was confirmed by Fourier transform infrared and ¹H NMR spectroscopy. A kinetic study of polymerization revealed pseudo‐first‐order kinetics with respect to monomer consumption. Initiator efficiency was found to be in the range 0.80–0.95. Matrix‐assisted laser desorption ionization time of flight spectra showed a narrow molecular weight distribution with control over the molecular weight. The reactivity of the allyloxy groups on polystyrene was successfully demonstrated by quantitative photochemical thiol‐ene click reaction with benzyl mercaptan as the model thiol reagent. Furthermore, the thiol‐ene click reaction was exploited to introduce other reactive functional groups such as hydroxyl and carboxyl by reaction of α,α′‐bis‐allyloxy functionalized polystyrene with 2‐mercaptoethanol and 3‐mercaptopropionic acid, respectively. © 2014 Society of Chemical Industry     

Artificial fish skin of self-powered micro-electromechanical systems hair cells for sensing hydrodynamic flow phenomena

Using biological sensors, aquatic animals like fishes are capable of performing impressive behaviours such as super-manoeuvrability, hydrodynamic flow ‘vision’ and object localization with a success unmatched by human-engineered technologies. Inspired by the multiple functionalities of the ubiquitous lateral-line sensors of fishes, we developed flexible and surface-mountable arrays of micro-electromechanical systems (MEMS) artificial hair cell flow sensors. This paper reports the development of the MEMS artificial versions of superficial and canal neuromasts and experimental characterization of their unique flow-sensing roles. Our MEMS flow sensors feature a stereolithographically fabricated polymer hair cell mounted on Pb(Zr_0.52Ti_0.48)O₃ micro-diaphragm with floating bottom electrode. Canal-inspired versions are developed by mounting a polymer canal with pores that guide external flows to the hair cells embedded in the canal. Experimental results conducted employing our MEMS artificial superficial neuromasts (SNs) demonstrated a high sensitivity and very low threshold detection limit of 22 mV/(mm s⁻¹) and 8.2 µm s⁻¹, respectively, for an oscillating dipole stimulus vibrating at 35 Hz. Flexible arrays of such superficial sensors were demonstrated to localize an underwater dipole stimulus. Comparative experimental studies revealed a high-pass filtering nature of the canal encapsulated sensors with a cut-off frequency of 10 Hz and a flat frequency response of artificial SNs. Flexible arrays of self-powered, miniaturized, light-weight, low-cost and robust artificial lateral-line systems could enhance the capabilities of underwater vehicles.     

A new framework for modeling coal devolatilization and combustion in boiler furnaces

This paper presents a new framework for the modeling of coal‐fired boiler furnaces. The input required for the model is the ultimate analysis of a coal sample. The model accounts for devolatilization followed by gas‐phase combustion. The devolatilization model used in this work is taken from published literature with slight modifications to match the numerical predictions with experimental measurements. This work also develops a reactor network model for simulating the performance of boiler furnaces. For the seamless integration of kinetic models of coal devolatilization and combustion with furnace numerical model, the thermochemistry data of several hypothetical and intermediate species involved in devolatilization chemistry are evaluated in the form of 14 coefficient National Aeronautics and Space Administration polynomials. The capability of the model for predicting the furnace temperature and product composition is demonstrated by simulating a single‐zone model. Copyright © 2017 John Wiley & Sons, Ltd.     

Analysis of Oil Debris in an Aero Gas Turbine Engine

Oil debris count is an important health monitoring parameter in aero gas turbine engine. Present paper deals with the oil debris analysis collected from the bearing houses and gear box of a military gas turbine engine. Due to relative motion between stationary parts, wearing-out has taken place in turbine bearing house. Improper assembly or dimensional inaccuracies found to be the root cause of high debris generation. For wearing-out of the drive shaft in gear box, lapses in assembly procedure and improper tolerances are found to be responsible. Though high ‘g’ maneuvers of the aircraft, hard landings, missile launch and bird hit or foreign object impact can lead to such high debris in the oil circuit, utmost care needs to be taken during assembly.     

Nanorefrigerants for energy efficient refrigeration systems

Journal of Mechanical Science and Technology - Nanorefrigerants, which are a new class of nanofluids, are mixtures of nanoparticles and refrigerants. They have several potential applications in...     

Experimental studies of gypsum plasterboards and composite panels under fire conditions

Gypsum plasterboards are commonly used to protect the light gauge steel‐framed walls in buildings from fires. Single or multiple plasterboards can be used for this purpose, whereas recent research has proposed a composite panel with a layer of external insulation between two plasterboards. However, a good understanding of the thermal behaviour of these plasterboard panels under fire conditions is not known. Therefore, 15 small‐scale fire tests were conducted on plasterboard panels made of 13 and 16 mm plasterboards and four different types of insulations with varying thickness and density subject to standard fire conditions in AS 1530.4. Fire performance of single and multiple layers of gypsum plasterboards was assessed including the effects of interfaces between adjacent plasterboards. Effects of using external insulations such as glass fibre, rockwool and cellulose fibre were also determined. The thermal performance of composite panels developed from different insulating materials of varying densities and thicknesses was examined and compared. This paper presents the details of the fire tests conducted in this study and their valuable time–temperature data for the tested plasterboard panels. These data can be used for the purpose of developing and validating accurate thermal numerical models of these panels. Copyright © 2012 John Wiley & Sons, Ltd.